Conference vmszoo::rc

    At our last club meeting, there was a demo on vacuum bagging given by a
    local sailplane guru.  He displayed a nice pari of windsong wings, and 
    had a few things to say that sounded worth repeating.  Since my 
    personal experience level is zero, these are quotes, not guarantees.
    
    A good source of bags is a moving company.  They use them to protect
    rolled up area rugs.  Since its a tube, any length is possible.
    
    More than about four to six inches of vacuum will tend to deform the 
    foam, so just about any compressor or vaccuum pump will suffice, 
    including those tire inflators you see in KMART.
    
    When using a pump/compressor, his approach to cheaply regulating the
    vacuum was to control the leaks.  Starting with some leakage, he
    would massage the seams until the vacuum was satisfactory.
    
    For caulking, he recommended ordinary window caulking that comes in a
    strip rolled up in a box.  I didn't note the brand, but he didn't act
    like it mattered either.
    
    To prevent blocking the vacuum hose with the plastic bag, he prefers
    to insert a strip of paper toweling on one side of the bag. 
    
    The hand pump with vacuum gage sold for bagging is a standard item 
    available at heating and airconditioning supply houses for about
    $16.00, significantly less than the price at the WRAM show.  With that,
    however, you must achieve a very good seal which will last for the cure
    time of your chosen adhesive. 
    
    He emphasized that the mylar needed to be at least six mil, and he 
    was using some with a graph pattern on the back that he bought at a 
    graphic art supply.  His gripe about using the mylar was that paint
    would not adhere to the surface unless he roughed it up with sandpaper.
    The frosted side of the mylar wasn't usable, because it had enough
    tooth, that the epoxy wouldn't release.

    I would stay away from the tubes for bag material.  Go down to your
    hardware store and just by some 6 mil visqueen (poor mans storm window
    materieal)  I bought a roll of this 8' wide by 100' long for $10.00 at
    a plastics supply house here in the springs.  Lay the bag out, set the
    wing on it.  put some caulking (squirted out of a gun, not the harder
    puddy type) around the three edges,  Then fold the bag over and smooth
    it out and squish the caulk down so it comes in contact with both
    pieces of visqueen, apply a generous amount around the vacumn tube hose
    and turn on the vacumn.  This is alot better because you are not
    picking the whole mess up and trying to slide it into a bag.  Everyone
    I have seen using the bag has had trouble getting it into the bag.  
    
    If you make the caulking a ways out from the wing, you can cut that off
    and have a new bag only smaller.  The Caulking will never harden while
    it is under vacumn because most caulks need air to cure.  
    
    We have even opened the bag up, let the caulk harden and then just
    reuse it again.  The last wings I did, I used a new bag ever time, it
    is cheap enough to not have to worry about pin holes and the such.
    
    Forget the tube just by the cheap stuff, and for caulking, the cheaper
    the better.
    

>    and turn on the vacumn.  This is alot better because you are not

This is getting good.  Now what do you turn on?  Are you using a
refrigerator compressor?  How do you regulate it?  Do you let it
run all night?  I'd be scared of letting a K-Mart auto pump run
very long - they get real hot real fast.

Bye          --+--
Kay R. Fisher  |
---------------O---------------
################################################################################

    I've vacuum bagged a few wings and certainly agree with Mark. Just use
    the visqueen for the bag. This has several advantages, including the
    ability to precisely line up the core on the beds. This will ensure a
    straight trailing edge. I saw one video tape where thy just hung the
    bag from the rafters while it was cureing. DON"T DO THIS. You will get
    a trailing edge that looks like a series of S turns. As for the caulk.
    I've tried several kinds. Almost anything will work. But I like the
    silcon based stuff the best. I just use my caulk gun and it works
    great. Don't fuss with the tube bag method. It's not worth it and its a
    hassel. I can make a bag in less then 3 minutes around the wet layup,
    and no hassels with getting everything precisely lined up and flat.
    
    As for the pump, if you use a manual one (excuse the pun) you may be
    one busy sucker. Any leaks at all and you won't be able to keep up. I
    also use 24 hr. epoxie. Bag time is a minimum of 14 hours. So use an
    electric pump. I made mine out of a G.E. refridgurator. I works great.
    It's quit and can pull 22 in. Hg. That's not bad at 7K feet. I
    regulate down to 15 in. Hg. for bagging. This is done with a pressure
    switch that a friend custom built. You can by a mechanical one however
    for about $30. As for running all night, no problem. The duty cycle is
    about 8 seconds out of every 2 to 5 min. The pump, doesn't even get
    warm. But if you have a larger leak, the pump can run longer. But you
    don't have to worry about working the pump while you find and fix the
    leak. The total I have invested in the pump, not counting the switch is 
    $15. Almost every thing was scrounged for the junk heap. 
    
    The Mylar we use in the PPSS is 14 Mil. This is very critical. Too thin
    and waveiness and wrinkles will show up. Too thick and it might not
    conform to the shape properly. I've tried 6 and 10 mil and will not use
    them. 
    
    Has for painting, I use Hexcell Epolite epoxy. This stuff is white and 
    the finish is such that you don't need to paint, providing you want white.  
    If you don't want white, scuff it and paint has normal.
    
    Now a plug. The PPSS monthly newsletter is full of good stuff on this
    and other topics. You can join the club and get the newletter for
    $8/year (outside Co. only). The only reason I mention this is that 1. The
    PPSS is a non-profit org. and 2. We need the money to pay the lease on our
    new flying site. So if your interested send me a note. And I'll get you on
    the mailing list.
                                                                           

>    regulate down to 15 in. Hg. for bagging. This is done with a pressure
>    switch that a friend custom built. You can by a mechanical one however
>    for about $30. As for running all night, no problem. The duty cycle is

Wouldn't a mechanical regulator be like the second stage of my compressor
regulator - that is it would maintain say 22 in Hg. on one side and regulate
to 8-15 (adjustable) in. Hg. on the other side.  But this would not be
switch regulated to the motor so it would run all the time - right?
If this is true can the motor do that for 24 hours without problem?

Speaking of compressors - it sure seems silly to be looking for a refrigerator
motor when I have a nice air compressor setting 10 feet away.  Is there any 
way to hook up the air compressor to work backwards?  After all you can
use your vacuum cleaner to work either way!

Bye          --+--
Kay R. Fisher  |
---------------O---------------
################################################################################

    While it is true that you do want to regulate the vacume, you really
    want to control the pump and have it shut off when vacumn it is say 15"
    of HG and turn it back on when it is at 14".  You dont want the bag
    flucuating in vacumn.  You dont want it to do from 20" to 10" every 3
    minutes.
    
    The trouble with most pressure switches is the dead band (that part
    between on and off) is generally pretty wide say 10psi.  You want a
    vacumn switch that is good for say 30" of HG and a dead band of 1-3
    maybe 5 inches.
    
    I would not recomend running a compressor as a vacumn device.  They are
    designed to blow not suck.  A vacume cleaners is designed to Suck not
    blow.  Hold your hand over the vacumn cleaners exhaust and notice how
    hot it gets.  Your compressor is going to do the same I would bet.
    
    There are devices where you can generate vacumn using compressed air
    but I believe they are not good for much vacumn because they are not
    very efficient at doing this, kinda like making 120VAC with 12 VDC.
    
    Keep up the good ideas and questions though.....
    
    The trouble you find with regulators is the dead band part of them. 
    Most Air compressors have a dead band of say at least 10 psi.  You want
    a vacum 

    I agree with Mark. What you want is a pressure switch. The one I use
    was made by Dave Kurth (PPSS Member) and uses the same transducer he
    used to make and in-plane altimeter. This switch is setable and Dave
    designed in a 1 in. Hg dead band. It is also important to have a vacuum
    tank to keep duty cycle low on the pump. The real advandage of the
    refirg. compressor is that it's quiet. You can hardly tell when it's
    running. As for running all night, I bagged some stuff last night, this
    morning I had 15 in. Hg on the bag and a pump cold to the touch.
    
    I would say the best way to lean whats required and improve your
    technique is to bag some stabs. There small, easy to do, and cheap.
    Remember, the pump is only a small part of the process. I think you can
    count on ruinning a few things till you get all the steps down, what
    layup to use and learn techniques etc. What I've discovered is that
    this is "real" process and to get good results you need good planning
    and to have your act teogether. It's no fun standing there with a
    bucket full of setting epoxy while you try to figure out how to save
    your wing from becoming a very hard pretzel.
    
    Ron 
    Ron

    We have one of those food sealers advertized on TV. The vacumm type.
    It's supposed to pull 27 PSI. I've been wondering how to integrate
    it into a vacumm bag. Any ideas?
    
    Tom

    Gee Tom, I've never seen any of the food sealers. But I don't know
    why you couldn't use it. You probably would want a vacuum reservoir and plug
    the pump into it. Then run from the reservoir to the bag. Reliability is
    the name of game however, or you might destory your wing if the pump died 
    during the process.
    
    The 27 PSI must be measured on the output side of the pump, as its hard to
    go past one atmosphere of vacuum. I think the ideal pressure is 7 to
    10 PSI . Any more is over kill and you run the risk of compressing the 
    foam. A little pressure goes along way. Assume you have a 500 sq. in
    wing panel, at 10 psi, that's 5000 lbs pushing uniformly down on you
    wing. Thats more than my Colorado Cadillac weighs!
    
    Ron    
       

    What kind of layups and epoxy are people using for wings?  Also I'm
     intrested in weight/sq.in. of the finished wing. Ones I've done come
    in at around .045 Oz./sq.in.  

    
    
       I hope you will excuse this novice question, but what is and why
    vaccum bagging?.
    
        Jacques
    
                

    Re: .-1, Jacques,
    
    Vacuum bagging is the latest method for applying pressure to wing skins
    epoxied onto foam wing cores.  I've never done this but, basically, the
    technique is to apply the epoxy to the foam core, put the balsa/ply/ 
    veneer/etc. wing skin(s) in place, then place the entire assembly into
    a vacuum bag and pump the air out.  This applies firm, even pressure to
    the skin(s) while the epoxy cures and is superior to the older
    techniques, all of which involved weighting the assembly in some manner
    or another.
						 __
				|      |        / |\	   	       
      	         \|/		|______|__(o/--/  | \	   	       
      | |        00	       <|  ~~~  ____ 04 ---- | --------------------
    |_|_|        (O>o		|\)____/___|\_____|_/	   Adios amigos, Al
      |     \__(O_\_	        |	  |___/	 o	   (The Desert Rat)

    I finally got a Sucker Kit (tm) and have just finished bagging a
    124" polyhedral wing for use on my Pulsar fuselage. 
    I used obechi over white foam and Pacer laminating resin.
    
    The Sucker does the job with a minimum of fuss. Takes about 100
    strokes of the pump to start applying significant pressure to the
    skins, then 50-60 more to make sure you've maintained the vacuum.
    
    I used 3M caulking for the bag sealent, and as long as you make
    sure there is a good seal around the suction tube this is fool proof
    stuff.
    
    For $60 you get the pump, 2-3 ft. of plastic tubing, ~13ft. of vinyl
    bag, and a small funnel.
    
    Terry
    

    Do you expect to be using standard heavy plastic to fabricate bags in
    the future? Can you reuse the bags reasonably well? What's the funnel 
    used for? Did you use the wing saddles while bagging? On the outside 
    of the bags or inside with a separator? How were the included instructions?
    
    I'm considering one of these for my Xmas list and would be interested
    in some of these details here or off-line. I'm hoping to build the
    hands off foam cutter and this might be the ticket for covering them.

    I saw the video on using the Sucker pump for vacuum bagging. I also saw
    the video on vacuum bagging where the guy (different) uses a vacuum
    pump, vacuum gauges, and a vacuum switch that turns on the pump
    automatically whenever the vacuum drops below x mm Hg, and shuts it off
    when it goes above y mm Hg.
    
    Given the evidence, one technique implies that one can create a bag
    with little or no leaks, while the other implies that the bag is prone
    to leaking, and so ya got to monitor (automatically, via vacuum switch)
    all the time. Who is right, and what's the bottom line?
    
    This seems to remind me of the metal engine mounts (super rigid) that
    some advocate, while you have the shock absorbing mount (super pliant,
    relatively speaking) that other swear by. Engines like one or the other
    or both (i.e. don't care?).
    
    And I thought only uncivilised Injun tribes resorted to hocus-pocus,
    but this seems as good pale face mumbo jumbo as any !! :-) :-)
    
    

    re. .-1
    
    I've got some 6 mil plastic sheeting that I'll be using in the future.
    The sheeting that comes with the kit is at least 8-10 mil thick,
    thicker than necessary, but it is easier to work with. It can be
    reused if your caulking isn't too sticky to pull loose after each
    bagging. Unfortunately the 3M caulk is so sticky that cutting the
    caulk bead off is the only way to open the bag. I can't find the
    less sticky brands of caulk locally.
    The funnel is used with a vacuum cleaner to pre-evacuate the bag.
    It isn't necessary, I didn't try it.
    I used the top wing saddle temporarily, on the outside of the bag,
    only while pulling the vacuum then clamped the trailing edge between
    two straight edges. I used fiberglass tape as a t.e. stiffner
    between the sheets on the inbd. panels, and carbon fiber tow on
    the outbd. panels. Both came out very straight and stiff.
    The instuctions are ok, a summary of what is covered on the video
    tape, #7 in the DECRCM video library, I believe.
    
    I discovered you need much less epoxy than when using weights
    and a piece of wax paper between the wood and the paper towel wicking
    will result in less clean up of excess epoxy that is forced through
    the wood, or rather you won't spend as much time pulling or sanding
    bits of paper towel offthe wing.
    
    I'd recommend this as a simple system that can be used in the house
    without compressor noise, etc.
    
    Terry
    

    re .22
    
     Well, I only have ready access to Apache, Navaho, Zuni, Pima, and
    Isleta tribal folk wisdom and they were all convinced long ago that
    I'm crazy. Other than that, seal the caulk well with a small wall
    paper roller, and you're in business. I had only one leak in four
    sessions, when I didn't seal well around the suction tube. 
    The kit comes with two clamps to pinch the line off. I used 10"
    Hg on the gauge, and it held for the 12 hours that the cores were
    in the bag.
    The electric pump, press. sw. routine seems way to much trouble
    to me.
    
    Terry
    

    re. 24
    
    I used two bags for 4 panels and two stab panels, but that was for
    technical resons, i.e. stupidity.
    Figure on losing ~ 1 in. of bag per bagging if you cut the bead
    off.
    The trick to getting a good seal is to place the caulk at least
    1/2 " inside the lip of the bag. This allows it room to spread
    out over the max surface area when you mash it down.
    
    Terry
    

    When using glass cloth and epoxy as the outer layer in bagging foam
    cores, it's necessary to use mylar sheets laid on top of the glass
    in order to get a smooth surface. The mylar is then peeled off after
    the epoxy is cured....but you already knew that.
    
    Mylar sheet is expensive and hard to find, but I think I've found
    a workable substitute. Locally it is sold in hardware stores as
    'Visi-Tuff', and is used as wind insulation over doors or windows,
    or wherever clear vision through the insulation is required. It
    is about 14 mils thick, made of vinyl, and sells locally for
    $1.19 a linear foot in 3 ft. widths, up to $2.49 a foot in 6 ft.
    widths.
    
    I've tried epoxying it to spruce and to itself, and it just falls
    right off after curing and removing the clamps. So it should peel
    off the glass after bagging, even better than mylar does.
    
    I'll be bagging some blue foam stab cores using .58 oz. cloth as
    the outer surfaces, using the Visi-Tuff in place of mylar. Will
    report on results.
    
    Terry
    

    My impression is that mylar adds value through its stiffness, so that 
    it minimises waves that might result from variations in the amount of 
    epoxy.  Is the vinyl fairly stiff as well?  Most of the stuff I've 
    seen has been pretty soft. 

    The vinyl is more flexible. I doubt that would be a problem over
    an area the size of a typical model wing. The pressure from the
    bag is such that the epoxy will be forced out into a pretty uniform
    film anyway. We'll see.
    
    Terry
    

    Terry,
    
    If I'm reading this correctly, you're just using glass cloth and resin
    in the bag? How do you get the right amount of resin on? From reading
    .6 (John Chadd) he puts the resin on the core and then places the cloth
    over it and squeegees it out. I this correct? From reading the sheeting
    methods it seems that you put the epoxy onto the sheeting and squeegee 
    it almost all off (until there's just a slight sheen) and then place it 
    on the core. Enquiring minds want (to get it right ;^)

Jim,

Never put resin on to he cores directly. The resin will penetrate the holes in 
the foam and add weight without strength. The additional weight is significant, 
as much as 4-6oz on a 40 size model. Always put the resin on the sheeting 
material not the foam, then apply the sheeting to clean cores.

I have used glass directly on to the cores. I did it by laying up cloth 
on a sheet of polished and release agent treated  window glass. The resulting 
sheet will be smooth on one side (the side of the glass) and still have some 
roughness on the other for the binding to the cores.

I don't think it is as ridged as balsa sheeting but I cannot quantify that 
statement.

John

    John speaks the truth when he says to always put the epoxy on the
    sheet, never on the core. Although now I'm a little confused about
    his using the window glass to obtain a smooth outer surface. 
    John, do you put the window glass in the vacuum bag along with the
    core ? I can't visualize this working.
    Using glass cloth as the outer surface, I would tape two pieces
    of mylar, vinyl, or whatever I'm using to obtain the smooth outer
    surface, together along their trailing edges, tape on the outside.
    Then I'd lay the glass cloth down on the vinyl, pour on the epoxy
    and spread it out thin over the cloth, squeegeing out the excess.
    Then lay the foam core bottom side down on the bottom half of the
    cloth. Now fold the top half of the cloth along with its vinyl or
    mylar sheet up over the top of the core. Now you have a sandwich
    with the core in the center,the cloth and epoxy directly against
    it top and bottom,with the mylar/vinyl being the outer surface
    contacting the vacuum bag. Check alignment of the core and cloth
    all around, wipe off any stray epoxy and pop the whole thing in
    the bag. After you've pulled the vacuum and everthing looks good,
    clamp the trailing edge between two straight pieces of 1" x 1/8"
    spruce or similar. Clothes pins are ok for clamps you only need
    to hold the trailing edge straight. The vacuum is already giving
    as much pressure as you need. Remember the spruce clamp pieces and
    the clothes pins are outside the bag. 
    
    Terry
    

    Thanks for the clarification. The Video is in the mail I've been told
    (but to where he asked ;^) I'm also building one of the hands off
    cutters so foam wing production will be the theme of this building
    season. I've read about the use of drywall spackle as a filler for the
    pushrod tube troughs. Is there any special concern with using it in the 
    vacuum bag environment?
    
    I guess that's why I have 2.5lb panic wings... I buttered the cores to
    put on the sheeting ;^) I think the next set will be a little lighter.

>    John, do you put the window glass in the vacuum bag along with the
>    core ? I can't visualize this working.

No Terry, I lay op the cloth as a separate exercise and once it is cured use 
the resulting sheet as I would a sheet of wood veneer. 

John

    re .34
     Sheesh, of course ! Where was my brain? I've seen the results of
    this technique and it does make nice panels.
    
    re. .33
    
    Jim, I'd be careful about using spackling compound over large areas,
    such as large dents or long narrow slots. The pressure from the
    bag is such that it can easily compress the spackling down below
    the surface, leaving a 'nice' groove in the sheeting. You could
    experiment to determine how much vacuum your particular brand will
    stand. I can tell you that Red Devil brand doesn't like to see 10"
    Hg when used under obechi on white foam. I'd consider filling the
    slot with a strip of balsa and carefully sanding flush. The spackling
    works fine if you don't try to fill too large of an area.
    
    Terry
    

    Jim,
    
    Depending on the way that you are running pushrods for the foam,
    you might be able to stay away from cutting a groove....
    
    Use a piece of brass rod and a torch...  Heat the rod and push it
    through the foam to where you want to go, effectively "drilling"
    a hole in the foam.  Then you don't need to worry about spackling..
    
    This is a bit tougher if there are lots of curves needed, but it
    should work OK...
    
    jeff
    

    My experiment using clear vinyl sheet in place of mylar, worked
    out pretty well.
    I bagged two blue foam stab halves using .58 oz. glass cloth as
    the only covering with a strip of carbon fiber tow full length under
    the cloth for stiffness.
    
    One silly problem was that the vinyl becomes nearly invisible when
    cut into small stab size pieces, the overhead flourescent lighting
    and the newspaper over the work area both conspired to make it nearly
    impossible to tell where the edges of the vinyl were. Then after
    laying the cloth out on it and wetting it out with pale yellow
    epoxy, everything disappeared, and I had to keep my nose down on
    the bench to tell when the edges of the cloth were wet out.
    Next time I'll use the blue tinted vinyl and a plain white paper
    over the work area.
    After taking the stabs out of the bag , the vinyl fell right off.
    I was impressed at the proverbial glass like finish, considering
    how thin the cloth/epoxy layer is. The trailing edge was literally
    knife edge, I cut it back to ~ 1/64" thickness for durability and
    safety. 
    I'm convinced that this is a usable technique.
    
    Terry
    

    Well, preliminary success at bagging a wing!

    On Thursday night, Al Ryder and I got together to bag the first panel
    of the Eindecker project.   We were sheeting a core cut from white 
    insulation foam; sheeting it with 1/16 balsa.

    We tried a number of variations to maintain the vacuum.  The setup 
    we ended up with was a compressor from an old fridge hooked to a 
    vacuum gauge (actually, it was a hand vacuum pump with a gauge 
    built in) hooked to a 10(?) gallon air tank, connected to the bag.

    We used 4 mil vinyl for the bag, and Hexall epoxy.  We spread the epoxy
    with old business cards.

    Things we learned:

    1 - The air tank used as a vacuum reservoir made all of the difference
    in the world in maintaining constant pressure.

    2 - Attaching the compressor directly to the bag (without an automatic
    switch) WILL crush the foam (our leading edge is measurably
    inconsistent).

    3 - Build the bag ahead of time...  We laid the the vinyl open and put
    caulk down on 3 sides..  After epoxying the sheets, we closed the bag
    around the whole mess...  This led to wrinkles in the seam that turned
    into leak points.  If we had built the bag first (and flat) we would
    not have had the wrinkles.

    4 - you REALLY need to maintain a warm enough environment for the epoxy
    to cure.  Al's house at 60 degrees took well over 12 hours to kick.  

    Questions:

    1 - Has anyone ever tried to use a heavy duty garbage bag as the bag??
    Any problems with the seal??

    2 - Anyone know where we can pick up a vacuum switch cheap??

    Future Changes:

    1 - In light of the fact that we have 23 more panels to build for the
    Eindecker project, we are going to add a manifold (distribution panel)
    to allow us to bag multiple panels at a time.

    2 - The compressor puts out very hot air.  We are likely to build a
    curing box..  The exhaust air will be circulated in the box to help the
    epoxy cure.


    Al, anything to add??

    cheer,
    jeff

    To maintain a constant and less than extreme pressure without a switch,
    I put an aquarium air valve just in front of the compressor to bleed in
    air at a finely controlled rate and let the compressor run constantly. 
    This worked very well, albeit with a hot pump.

        bag---->tank---->gauge------------>pump
                                   ^
                                   |
                                 valve
                       air---------^

    I'm not too happy with this set-up.  I'm pulling epoxy vapors through
    the expensive hand pump with unknown consequences, so today I bought a
    bare gauge that I'll rearrange to be off to the side of the air path on
    a tee.  The pump runs very hot pulling 10 inches of vacuum; the exhaust
    air was measured to be 140 F +- 10 F; a switch would be an improvement. 

    Some sort of fumes/dust/mist was coming out of the exhaust all night
    and filled the air in the room; what stuff am I pumping?

    For the second wing, the pressure never went beyond 15 inches, but the
    foam thickness at the leading edge still varied.  How little pressure
    can I use and still get a good bend and bond?

    8 inches of vacuum is sufficient for white foam and balsa. With
    blue foam you can go to 10-12 inches.
    My hat is off to you guys using electric vacuum pumps. I guess they're
    necessary if you want to do multiple panels in a short time.
    
    Terry

    Ah..  Perhaps Al's new gauge will be more accurate in the 0-10 range.
    The one we were using was a bit sticky in that range...
    
    The electric pump really is quite nice, even on single panels (although
    I guess it is a bit of over kill).  But it really makes the resevoir
    tank useful...
    
    cheers,
    jeff
    

    I have guess about the mist in the exhaust. If the pump your using is a
    refridg. compressor I'll bet the mist is oil. The compressor is
    designed to be a closed loop system that recirculates the oil. When you
    vent the exhaust, you loose the oil. I built an oil seperator for mine
    using a 4" dia. plastic pipe and recirculate the oil back to the
    crankcase. The seperator is easy to build and looks like this:
               |--                           --
               |______________________________|
    Output   -------                         --------  exhasut to room
   from pump   |                              |
               |                              | Cap at both ends
               |____|_________________________|
               |    |                         |
                --  |                        --
                    |
                 Oil back to pump
    
    
    
    The hard part is figureing how to tap back into the oil resevior. I my
    case it was easy, in some it is not.
    
    Ron
    
                                                                      

>       <<< Note 91.42 by N25480::FRIEDRICHS "Take the money and run!" >>>
>                              -< bagging success >-
...
>    built in) hooked to a 10(?) gallon air tank, connected to the bag.

Where does one find a 10 gallon air tank (cheap)?

>    2 - The compressor puts out very hot air.  We are likely to build a
>    curing box..  The exhaust air will be circulated in the box to help the
>    epoxy cure.

If you notice the oil mist doesn't occur until after the compressor gets
REAL hot.  Just burning oil I'm sure.

But - with the 10 gallon air tank - I should think you could shutdown
the compressor once you get to 10 inches of mercury for the evening.

P.S.  My hand pump/gauge was also a source of leakage.  I had to take
the think out of the circuit to maintain vacuum.

Bye          --+--
Kay R. Fisher  |
---------------O---------------
################################################################################

    As I've been looking into this also. For about $15 you can get a good
    vacuum gauge from the autoparts store

    Ah, but where can you get a vacuum switch??  
    
    I have talked to a company called Kurt J. Lesker  and they have
    a switch for $$300-400!!  Does anyone know of a cheaper source??
    
    Thanks,
    jeff
    

    Re: .-1, Jeff,
    
    Auto air conditioner systems use a vacuum switch to protect the
    compressor (prevent it from burning up) under low freon situations.  I
    know absolutely nothing more about it, i.e. what it looks like, how
    big, whether part of the compressor, etc. but it might be something to
    look into.
						 __
				|      |        / |\	   	       
      	         \|/		|______|__(o/--/  | \	   	       
      | |        00	       <|  ~~~  ____ 04 ---- | --------------------
    |_|_|        (O>o		|\)____/___|\_____|_/	   Adios amigos, Al
      |     \__(O_\_	        |	  |___/	 o	   (The Desert Rat)

    I must be too dense to follow along, or something, but here's the
    way I see this vacuum bagging thing:
    
    1. A certain volume of air must be partially removed from an enclosed
       space.
    
    2. If this is a fairly large volume of air, then it would be nice
       to be able to remove it rapidly with the least amount of physical
       effort, i.e. an electric vacuum pump. 
    
    3. If it is a fairly small volume of air, as in the size of a bag
       used in modeling, then a simple hand pump works just fine with
       only moderate physical effort. If you don't plan on doing this
       more than a few times a week, most people will not be over-taxed.
    
    4. Therefore, once the vacuum has been established and the suction
       line pinched off, why worry about constantly running pumps,
       reservoir tanks, pressure switches, spewing oil fumes, et al?
    
    5. I do my vacuum bagging in my bedroom for gosh sakes (c'mon punks,
       think of a joke) ;^)
    
    Terry

    re  why keep pumping

    Our set-up had leaks, and from what I've heard, leaks aren't that
    uncommon.  The tank helped, but over a few hours the pressure would
    drop to a few inches, hence the need to pump at least intermittently.

    re the hand pump and the leaks

    Mine will hold 29 inches persistently.  The leaks were in the bag area.
    It is possible that the 4 mil poly is a bit porous; it is much more
    likely that our seals were at fault.  Next time I'll fabricate the
    bag while it is flat as Jeff suggested.  Also, the rope caulk may be
    partially at fault.

    re the mist

    Oil droplets are consistent with my observations.  Hot at the source,
    but probably not burning.  Low duty cycle intermittent pumping should
    solve that.  But if we are depleting the oil supply, it would seem
    prudent to suck in some oil now and then.

    re the gauge

    The sticktion in the hand pump gauge was not unexpected nor a problem;
    a tap with a finger caused enough movement.  I bought the new gauge to
    preserve the pump.  The new gauge was $12.50 in the plumbing department
    of County Store, a local [and very high priced] hardware store.  I
    suspect that an automotive [dashboard?] vacuum gauge would be
    sufficient and less expensive; it might need calibration; I paid top
    dollar on impulse, not that anyone else would do such a thing.

    re a vacuum switch

    From RCM 1/87 page 141 a reference I'll put into 9.22, the mail order
    topic.  It would get lost at the end of this long-winded reply.

    Alton, having fun learning

    My tank was bought at Sears for a pressure reservoir when I painted my
    house twenty years ago. Intended for high pressure, not mild vacuum, it
    is very sturdy in this application.  The volume is 9 gallons, probably
    sold as "a 10 gallon tank".  A length of schedule 40 waste line with
    end caps might be a better buy.  Inward 15 psi is wimpy.

        I recently picked up a freon refrigerant canister (green) from the
        service tech recharging our computer room a/c system. It is about
        a foot in diameter, and roughly a foot tall, making it something
        like 5-7 gallons capacity. It looks like a perfect candidate for
        use as a buffer either for vacuum pump / baging operation, or my
        compressor / airbrush. I believe that the tank was marked 120PSI,
        but it was also marked DO NOT REFILL, so they just discard them.

RE: 91.55

I've got one of those green freon tanks. Go take a look around Auto 
Shack or your local well stocked hardware store. There's a kit you 
can buy for about $17 to convert the tank into a proper air tank. 

RE: Note 91.56 by STOHUB::JETRGR::EATON 
> I've got one of those green freon tanks. Go take a look around Auto 
> Shack or your local well stocked hardware store. There's a kit you 
> can buy for about $17 to convert the tank into a proper air tank. 

    What do you mean "conversion kit"?  What is there to convert?  Do
    you mean just a few fittings to change the thread size?  Is there a
    check valve included?

    On another (related) topic; When I was in Dallas during my Dec./Jan.
    vacation, my dad took me to a surplus place that has compressors for
    $10.  I bought 2 of them.  These will pump up to 50 psi or, if you
    hook up to the other port, will draw 20 inches of mercury vacuum. 
    These pumps are designed for continous duty and have a built in fan
    to make sure they don't overheat.  They also don't omit any oil
    "mist" or any related "bad stuff".  

    >>>>>>  In other words, they make PERFECT vacuum bag pumps.  <<<<<<

    The surplus place has lots of them (approx 40?) and they are all
    $10.  If anyone (in New England) is interested in seeing what they
    look like, I'm going to bring it to the DECRCM meeting next Tuesday. 

    My dad said he'd be glad to buy (and ship) one for anyone that wants
    one.  Of course you'd have to pay for the shipping too.  (approx.
    $5.-$10. for shipping.)  They weigh approx 12-14 pounds.

    I am now working on a vacuum switch that uses one of the new silicon
    chip pressure sensors.  I got the sensor as a free sample, but they
    retail for about $13.  I'm guessing that the additional parts
    required will cost less than $5.  The only other item required is a
    120V 10A relay to actually switch the compressor on & off.  (I got a
    few of these relays at a flea market for $1. each.)

    I'm also looking for a vacuum tank and was planning on getting an
    empty freon (free-on :-) ) tank.  I've just been too lazy so far to
    call around to find one...

                       _____
                      |     \
                      |      \                          Silent POWER!
      _        ___________    _________   |            Happy Landings!
     | \      |           |  |         |  |
     |--------|-  SANYO  + ]-|  ASTRO  |--|              - Dan Miner
     |_/      |___________|  |_________|  |
                      |       /           |     " The Earth needs more OZONE,
                      |      /                       not Castor Oil!! "    
                      |_____/

    I just took apart a water system pressure switch with conversion on my
    mind.  It *could* be done, but it isn't worth the effort.  Now to try
    an automotive parts store.

    Check out Blakeslee's column in the March MA, pg 49.

    I just ran into another type of pump that might be used for vacuum
    bagging, and that's a pump used in the machines for milking cows. Now I
    haven't the slightest idea of where one would find one of these things,
    but thought that this information might be useful to someone in
    RC-land.
    
    	Marty Sasaki

    I followed up on Marty Sasaki's lead and called a dairy farming
    friend.  Close but not quite a solution.

    Milking machines run at about 15 inches of vacuum; that's the good
    news.  The bad news is that: 1) the regulation is by bleeding air into
    the intake line (like my aquarium valve approach), 2) the new
    regulators are not adjustable, and 3) the pumps themselves are multiple
    horsepower motors.  So I cannot reasonably solve my pressure regulation
    problem by buying a milking machine component.  I cannot take my bags
    to the farm because they only run the pumps while they are milking.

    Good ol' Bag Balm. The farmer's cure all.
    
    Jeff and I were talking while cutting cores last night and your multi
    bagger could be a leak nightmare. You're going to have to have some way
    of shunting off individual lines so you can isolate a leaker. The
    Eindecker core that Jeff brought along looks great. I was amazed at the
    toughness of the sheeting.

In a book that Kevin Ladd has they solve the vacuum switch with a car
vacuum diaphragm.  You just hook up your vacuum line to the diaphragm
and position wheel collars on the output mechanical shaft.  Then the
whole thing is mounted on a board and a micro switch is tripped
by the wheel collar.

I read the book - but I have never tried this.

Bye          --+--
Kay R. Fisher  |
---------------O---------------
################################################################################

    Another source for vacuuming bagging supplies, cloth, CF, Kevlar,
    kits, epoxy, etc:
    
    Weston Aerodesign
    944 Placid Court
    Arnold, Maryland 21012
    301-757-5199
    
    
    They have a complete vacuum bagging kit for $180. It includes pump,
    15ft. of hose, 4-way valve, vac. gauge, 20ft. of 6 mil poly bag,
    sealants, distribution manifold, 6ft. of bubble mat, 6ft. of 47"
    Mylar.
    Vacuum pump alone is ~$125.
    
    They also have a line of kits, Sam,Merlin, Magic, Terminator.
    Also available pre-built, ready to fly.
    

    Today I went to PEECO, a place in Hudson Mass that sells vacuum
    switches. They have their low price one in stock on the shelf, 
    
    and there it shall remain at a price of $110!

    The approach of Kevin Ladd's book is looking better every hour.

    I think I have another, especially since I don't have a suitable vacuum
    sensing diaphragm.  I have a vacuum gauge with a pointer.  What if I
    remove the glass face and put two wires in a position to touch the
    pointer as it passes them.  Then I connect a 555 timer chip with the
    reset at the high vacuum wire and the trigger at the low position.  When
    the pressure drops to the trigger wire, the output goes high, driving a
    relay (up to 100 ma DC?).  If pin 6 (threshold) and 7 (discharge) are
    tied to ground, the output will remain high until the pointer climbs
    high enough to touch the reset wire, then the output drops to nil.  Now
    I haven't even thought of a 555 circuit for a long, long time, but I
    think this will work.  Comments are requested --- especially any
    suggestions about driving an inductive load directly from a 555.

    those sprung pointers are pretty delicate and electrical contact would
    be kind of iffy (the pointer is painted, drag on it will make it stick,
    etc.). I think you might be better off persuing the vacuum
    advance approach that Kay mentioned since it's meant to move something
    a little more substantial (carb kickdown) You could probably scrounge
    one at a local junk yard for a couple of bucks and then you just need
    to tie it in like the pressure gauge and set up the collers since it
    already has the rod coming out of it.

I think that i'd try the car vacuum switch first but one way to sense the
position of the vacuum gauge pointer would be to put some reflective tape
on the pointer and use a couple of optical position sensors (i've seen them
for a couple or three bucks apeace) to turn the 555 off and on. The 555 has
a few hundred mils of drive current so it could activate one of the small pc
mount relays with no problem. Just be sure to use clamping diodes so that
inductive spikes wont blow the 555's output stage. That actually might not
be a problem with the small relays but i've been bitten by it before so i'd
throw the diodes in just in case. 

Glenn

    Another pressure switch idea is to use a silicon pressure sensor
    with a simple op-amp circuit.  I have schematics for this
    application that is in the data book for the sensor.  It is a very
    simple circuit that uses only one op-amp chip (LM324 or equliv.)

    Approx. cost:
      1  Sensor (SCC15A) $12.95      (I got mine as a free sample)
      1  Op-Amp (LM324)  $ 0.36
         Res. & caps     $ 2.00  (approx)
      1  120 V Relay     $ 5.00  (??? - I got mine for $1. @ flea mkt)
      1  Power supply    $ 8.00  (approx - To drive Op-Amp ckt.)
         (Could be just "9V battery" or calculator AC adapter...)

    I figure complete cost including a nice box to put it in should be
    less than $35. or $40.  (Mine will be only $10 to $15 since I have
    most componets already...)  This would include 2 pots for pressure
    and ON/OFF range (hysteresis).

    Pressure sensor data book and sensors from:
            SenSym, Inc.  (A Fasco company)
            1244 Reamwood Ave.
            Sunnyvale, CA  94089
            (408)744-1500

    Note that these pressure sensors can also be used in altimiter
    applications...

    [ Insert standard disclaimer here... ]

                       _____
                      |     \
                      |      \                          Silent POWER!
      _        ___________    _________   |            Happy Landings!
     | \      |           |  |         |  |
     |--------|-  SANYO  + ]-|  ASTRO  |--|              - Dan Miner
     |_/      |___________|  |_________|  |
                      |       /           |     " The Earth needs more OZONE,
                      |      /                       not Castor Oil!! "    
                      |_____/

    This is a sterling success!  (And a week when I needed that.)  The
    *system* does four wings at a time.  The vacuum is rock solid (if
    you'll forgive my adjective) at 7 to 8 inches, the temperature in 
    the curing box is in the eighties, and the pump is usually off.

    Switch:

    I bought, tried, rejected, and returned an automotive switch.

    I bought, examined, rejected, and will return an automotive 
    distributor advance diaphragm.  The travel was only 1/8th inch at 10
    inches.  I could have amplified that travel, but the slop would have
    been amplified as well.  And when the 555 worked, I didn't need it.

    The 555 approach is easy, cheap, easily adjusted, and it works.  I
    protected the chip with a series diode followed by a reversed shunt
    diode.  I put a 1 K pull-up resistor on both sense leads.  The plastic
    face of the gauge was drilled for the two sense wires; although the
    pointer itself is painted steel, the edges of it are bare (a stamping).
    The relay has a 5 v coil at 100 mA and a rating of 10 A at 110 v.  The
    DC power supply is set at 7 v.  The assembly is a shameful crock; the 
    555 is rubber-banded to the relay as a dead bug, and point-to-point
    wiring is used.  The ground return is rubber-banded to the gauge body.
    But the sucker works!

    Manifold:

    I used a foot of 1 inch schedule 40 PVC with end caps.  (Actually one
    end has threaded fittings, but the next manifold won't.)  The new gauge
    is off one end and the suction line on the other.  The taps connect to
    cheap aquarium air line.  For line shut-off's, I initially used brass
    aquarium air valves, but the leakage was severe.  Folded lines with a
    clothes pin clamp work, but at a significant risk of dislodgment.  I
    bought and tried an electrical grounding lug for #10 wire; this is
    essentially a 5/16 tunnel with a large set screw to jam the air line as
    it passes through the tunnel; it works beautifully.  For connectors to
    the air lines from the bags, I used aquarium check valves.

    Curing box:

    We run the house cold at night, very cold.  So I made a box 3+ feet
    long and 2 feet square with the manifold inside.  An old hair dryer on
    its lowest setting kept the box in the high eighties all night.

    The bottom line:  a crock, but a WORKING and EASY TO USE crock.

    Next time the cores should be cut at least an inch or two longer than
    the finished wing.  To avoid tolerance problems, the veneer had been
    deliberately cut about an inch longer than the foam.  As a result, the
    overhang at the ends applied pressure without foam to resist it, and
    the ends of the wings are a bit thin.  The same would have been true of
    the leading edge if we had not trimmed the balsa to a more exact fit.

    Because the veneered wing is so easy to trim, I'm inclined to cut the
    cores overly long and to include the leading edge portion in the core.
    I would then rip off the leading edge if a solid wood one is to replace
    it, and the extra length would be trimmed when the dihedral is cut.

    Al,
    
    Since soldering irons are mostly for landing gear ;^), Could you
    provide a non-EE schematic for the relay switch that a software type
    could follow? I can find the parts and assemble them together but I
    can't make judgements as to what value is critical and what value can
    be any in a range.
    
    Also, are you using the manifold as a vacuum reservoir also or is that an
    additional piece in your "system"?

    The manifold is in front of the tank.  For a software type, the
    manifold provides multi-threading of the application solution.  The
    tank absorbs momentary loads during the addition of the extra bags
    and matches the pump to the load.  For a software type, the tank is a
    buffer pool.  This exercise ought to be fun when I get to the 555.
    I'll put the switch circuit into another note.

    Alton, who is on vacation today.

    The 555 as you buy it:
    
                          +---U---+
                 GROUND   1       8   V+            
                          |  555  |
                 TRIGGER  2       7   DISCHARGE  
                          |       |
                 OUTPUT   3       6   THRESHOLD   
                          |       |
                 RESET    4       5   CONTROL     
                          +-------+
    
    The 555 as it is used here:
    
    
                          +---U---+
    to supply and gauge   1       8   to + 7 volt supply
                          |  555  |
    to the low limit wire 2       7   no connection
                          |       |
    to the diode clamps   3       6   no connection
                          |       |
    to the high limit     4       5   no connection
                          +-------+
    
    The diode clamp circuit:
    
    from the 555 output --------->|--------+--------- to relay coil
                                           |
                                           |
                                          ---
                                           ^
                                           |
                                           |
    from the power ground -----------------+--------- to relay coil
    
    The first diode blocks a reverse voltage kick from the relay coil
    when the switch turns off.  The second diode dumps the stored energy
    in the coil.  The diodes are little ones --- unimportant --- I don't
    know which ones I used, but they would have been handy on the bench.
    
    The gauge sense circuits (identical):
    
    from the +7 v power ----------+
    (at pin 8 of the 555)         |
                                  /
                                  / 1 K, zilch wattage resistor
                                  /
                                  |
    from the 555 sense lead ------+------------------ to gauge pointer
    (trigger or reset)                      
                                            
    from the power ground --------------------------- to gauge body
    
    The resistors were handy on the bench; the values may not be optimum,
    but they are non-critical, and they worked.
    
    If a circuit designer will select better values, add R/S part
    numbers, and re-draw this, I'll delete this note.
    
    Alton, who is going to go play on this vacation day.

    That may not satisfy a purist, but I think I can build one from it.
    
    Thanks!

RE: Note 1209.55 by BRAT::RYDER 

    Alton, congratulations on your success.  Late last Sat. night, I too
    got my circuit working.  My circuit certainly can't beat yours for
    simplicity.  I have one op-amp chip but about 10 resistors vs. your
    1 chip w/ 2 resistors.

    The only portion of your design I don't like is the hokey "wires on
    the pressure gauge needle" part.  But, I don't think the rubber
    bands are all that much of a crock - you should see my setup!  :-)

    How much does a pressure gauge cost?

    I didn't get around to make a curing box yet because I don't think I
    need one.  Our furnace is in a small closed room and stays about 75
    degrees even when the thermostat is turned down.  This is also now
    the "vacuum bagging" room.  :-)  I know that expoy cures faster at
    higher temp, but at 75 deg., the epoxy cured overnight anyway...

    I like your idea for the manifold.  I've just been using glass jar
    with R/C fuel tubing with "T"s to get more lines if required.  (See
    diagram below.)  Is the aquarium air line similar to fuel tubing? 
    How (in)expensive is it?

    FYI - I got my freon tank for free from a local refrigeration
    service place.  If there any of you looking for a tank, just look in
    the yellow pages under "Refrigeration Equipment - Commercial -
    Servicing".  Call and tell them you want an empty "50 pound" freon
    tank.  They throw them away when empty as they are non-refillable.

    My vacuum lines look like this:

        [Pump]===========T===========[Freon Tank]
                         |
                         |   +----- To pressure switch
                         |   |
                         |   |   +--- To vacuum bag(s)
                         |   |   |
                    [Glass Jar w/ Metal top]

    I've been using the glass jar as my manifold and as a "trap" for
    excess epoxy that may get sucked through the bag lines.  In the
    metal top of the glass jar, I have a 1/4" I.D. line coming from the
    pump/tank "T" and a 1/8" brass tube that connects to the bag via
    fuel tubing.  A second 1/8" brass tube connects to my pressure
    switch (via fuel tubing).

>> I bought and tried an electrical grounding lug for #10 wire; [...]
    Great idea.

>> For connectors to the air lines from the bags, I used aquarium check valves.
    What are these and how expensive are they?  Do they leak at all? 
    Please explain further how you use these...

                       _____
                      |     \
                      |      \                          Silent POWER!
      _        ___________    _________   |            Happy Landings!
     | \      |           |  |         |  |
     |--------|-  SANYO  + ]-|  ASTRO  |--|              - Dan Miner
     |_/      |___________|  |_________|  |
                      |       /           |     " The Earth needs more OZONE,
                      |      /                       not Castor Oil!! "    
                      |_____/

    Interesting Dan, I used the exact same word ("hokey") to describe
    the wires on the gauge...
    
    The aquarium tubing is made from a different material and is stiffer
    than fuel tubing, but comes in about the same sizes.  Very cheap
    though, (like .10/foot).  If you ask nicely, maybe Al or I would give
    you 50 feet of it... (We both have spools of it from our other hobby).
    
    The check valve fits inline with the tubing to each bag.  It SHOULD
    prevent a sudden vacuum loss in the system from letting air into the
    bag.  I believe that Al found there was very little leak.  They only
    cost about $1.50 each at your local pet store...
    
    Congrats on your success Dan!
    
    cheers,
    jeff
    

re Note 1209.61 by Dan Miner,

>>    How much does a pressure gauge cost?

    $12.50 at a very expensive hardware store.  (County Store in Milford NH)

>>  the manifold.  

    I forgot to mention the taps.  I happened to have some polypropylene
    3/8 mp x 1/8th barb fittings, but I know of a better tap.  Aquarium
    shops sell 1/8th airline splice fittings; they have a small flange in
    the middle and cost about 25 cents retail.  Next time I'll drill a 7/64
    hole in the PVC, smear some RTV on one end of a splice fitting, and
    stick it into the hole; suction will provide the primary strength.

re  airline tubing

    Aquarium shop airline tubing is usually this very cheap 1/8th ID thin
    walled, clear vinyl tubing.  Jeff and I both bought 500 foot spools of it
    years ago for about $10 or so.  Since then I have bought some from a
    plastic supply house with 3/32 walls; much easier to work with. 
    Hardware stores usually sell it by the foot.  So no, it is not fuel
    line (which I believe is silicon).  I don't know local retail prices.

    The cheap line is fine for the bag entry --- disposable and OK to be
    wimpy.  I use the better line for the "permanent" set up lines.



>>  I've just been using glass jar .... with "T"s to get more lines 

    I think the jar is a superb idea.  The fitting mentioned above would
    work.  However, I would probably put all taps into the jar to get
    better bag-to-bag isolation at suck-empty-the-not-first-bag time.

>>  I got my freon tank for free from a local refrigeration

    I like the price.  My Sears tank was not free!  (But it is *old*.)

>>  aquarium check valves. ..... What are these and how expensive are they?  

    Rubber clarinet mouthpieces in a plastic can.

    Short lengths of rubber tubing, pre-flattened at one end, over a nipple
    at the other.  Air passes from the round end out the flat end, but
    cannot reverse.  The cost used to be about a buck apiece, retail.

    A new one will not leak.  My old ones aren't leaking, but that may
    change with time.

>>  Please explain further how you use these...

    Actually, my primary use is as a connector between the bag line and the
    manifold line.  But I happened to have them, so in they went.  At the
    same time there is a slight value as an isolator for the early bags
    when the later bags are being sucked dry.  So they are installed as air
    line "diodes" letting air our of the bag but not back in.


    Time to go flying!
    Eat your heart out, guys.

    Alton

At the WRAM show the guy in the Aerospace Composite Products booth
had a vacuum pump that can continuously and self regulated at 9.5 inches
of mercury.  Quite and small - $70.00.  Too new to be in any of their
catalogues yet.  He was working on getting a source for inexpensive
limit switches - but the best he has been able to come up with so far
will retail at $50 and his cost is $39 when he gets them in large
quantities.  I mentioned to him what Dan Miner was doing and he expressed
an interest.  Hey Dan, perhaps you could send him a working proto type
or give him a call and make a deal where these devices could be professionally
produced and marketed.  If I didn't already have one refrigerator pump
and one other pump due from Dan and one sucker kit - I would jump at the
$70 pump he had at the show.  It was kinda neat - plug it into the wall and
plug the vacuum into the bag - no need for gauges or any extra vacuum lines.

Bye          --+--
Kay R. Fisher  |
---------------O---------------
################################################################################

    I got a catalog from CST Technology, Lancaster, Ca. They have a
    cute little vacuum pump for $75, which includes all the material
    to get started in vacuum bagging. It's a self-regulated, continuous
    running type, about the size and shape of a small cereal box.
    
    After last nights experience in bagging the Chups wings, I might
    just go for this baby.
    I used a brand new piece of mylar, sealed it on three sides with
    caulking tape, slid in both wings with the trailing edges facing
    out so that I could clamp them between pine strips for straightness,
    sealed the fourth side and then the fun began. I couldn't get more
    than 5" on the gauge of the Sucker pump. I could hear the leaks
    in the corners of the bag. After plenty of hassling I got it up
    to 10"as long as I kept pumping but it would leak down to zero in
    30 seconds. I finally decided my caulking tape was dried out, it
    seemed less sticky than usual when I was applying it. It's cheap
    stuff (not 3M) and apparently doesn't like sitting in a box for
    months at <20 % humidity. Anyway, duct tape around all three sides
    saved the day, but it never would hold more than 5", sufficient
    for the 1/32" balsa and white foam.
    Silicon caulking from a tube wouldn't have this problem, but it's
    hard to clamp the trailing edges when using it because you can't
    slide the wings up against the edges of the bag without getting
    caulk on them. 
    I'll report on the CST pump, if I get it.
    
    Terry

    This is rapidly becoming a reality for me. I should be bagging my first
    wings in a couple of weeks and I'm heavy into the information gathering
    stage (just ask Mark Antry about bending his ear wednesday night) What
    weight glass cloth are people using for covering bare foam cores (using
    the mylar sheet method)? I'm looking at 2m to standard class wings
    currently.

    Ajai was into bagging way back last year. He gave a demonstration
    at one of the DECRCM meetings. As a matter of fact, he brought
    his WHOLE PLANE in in a bag. 8^)
    
    Steve

    Gawd. And silly me, I was going to ASSEMBLE them before putting it in
    the bag! ;^)
    
    Do you know what weight cloth he cried into while "bagging" the plane?

    The most popular choice is probably 2 oz. cloth, for conventional
    spar structures. Some people like to use heavier cloth at the root,
    tapering out to lighter cloth outboard.
    
    A neat but expensive method is full chord, and nearly full span,
    carbon fiber mat under the cloth. This reportedly allows a sparless
    wing.
    
    I'm going to shortly try 1 or 2 oz. cloth on white foam stab cores.
    The last time I tried cloth on foam, I used .60 oz. cloth. The weight
    and surface finish were ok, but the rigidity was barely good enough
    for stab use.
    
    I just received an electric self-regulated vacuum pump from CST
    Technology. It's regulated to 7" max. which is perfect for white
    foam and adequate for blue foam.
    
    For $75 you get the pump, 9 ft. of nylon bagging material (which
    seems to be much more abrasion/puncture resistant than the usual
    vinyl), 30  ft. of sealant caulking, 24 ft. of felt vacuum wick
    (this stuff looks like it came from a Santa Claus suit, paper towels
    work just as well), and the hose and t-fitting.
    It runs pretty quietly, especially if its put on a piece of foam.
    
    I also got a roll of mylar, and a tub of white tinting paste to
    add to the layup epoxy, in order to avoid having to paint the final
    product. The amount of coloration that the tinting paste adds is
    not up to museum scale standards, but it's adequate for a functional
    finish or as a base color. It can only be used with the clear type
    of laminating epoxy which is what most people use for cloth on foam
    anyway, unless you like brown wings.
    
    Terry

    Maybe this should be in the cutting foam topic but...
    
    What type of spar structures are we talking here? Can the spars be
    avoided by using carbon fiber between the glass and the core?
    
    Jim (who's not fond of cutting spar troughs)

    By conventional spars I meant the type found in Pulsars, Lovesongs,
    etc., spruce strips top & bottom that run out 50-80% of span.
    
    Carbon fiber mat under the cloth does away with the need for spars
    outboard of the wing tube box. The plane in the picture I sent you
    uses 12" tube box, no spars, carbon mat under the obechi sheet out
    to about 32", and .014 carbon fiber strip on the top only, out another
    20". That wing is plenty strong but heavy because I got carried
    away in the wing tube box structure. 
    
    Terry

    
    Back to the hazardous business of living in the wild west again, and
    doing my bit to defend injun backs against pale face knives...
    
    Who ever said the middle east was unsafe? :-)
    
    >>Do you know what weight cloth he cried into while "bagging" the plane?
    
    Dunno, Jim. Matter of fact, I could bring the bag along to the next
    meeting if ya want a second look. Don't remember using any vacuum
    though, just remember to use a bag plenty big.
    
    RE what weight cloth I cried into - I couldn't risk having my
    application for US citizenship rejected. You'd think wasting a 
    plane would be good enough, but I didn't want to take chances.
    
    So I cried into some paper napkins that are made by taking trees down,
    so there are less of 'em around to gobble up planes...
    
    ajai

Well when we made our KILLER F3b planes we used no spars at all and the layup
was 8oz bi directional cloth covered with a 3oz standard weave. You could not 
break these wings!!!!! NO ifs ands or butts.  Now this is a bit on the heavy
side for a glider but I think we got around 12oz wing loading with it.  I made
my 2m slope plane out of the same layup and it was a little heaver than I would
like.  My next 2m thermal plane will be some 3-4oz standard cloth with some 1.5-
2.0 cloth with a top and bottom strip of CF.  Be carefull about not getting 
enough cloth.  For example we tried some stabs with just 1 layer of 2 oz cloth
and yes while they are strong enough you could easily dent them with your 
fingers handeling them.  I would always try to get 2 layers of cloth regardless
of the weight.

Now, no spars you say.....  YES dont fool around with the wings trying to put
spars in them, the less you touch a good cut core the better.  Our spar system
on the F3b wings was a 1/4" ply root rib and a 1/4" ply carry through rib 
installed about 4 " in from the root rib, the wing rod tube extends through 
both of these and presto your in business.  Keep in mind the dihedreal when
figuring just how far out to install the carry through rib. Also 1/4" ply may
be a little big for your normal thermal ship

    One minor question on the multi-layer wings...
    
    Do you lay-up all the layers at once or do you do individual layers and
    sand between them to scuff the surface?

    re .73
    
    Mark, when you install the carry-through rib do you cut off a 4"
    piece of the wing root, then glue the rib to the outboard end of
    the piece, then glue the 4" piece back onto the main part of the
    core ? Or do you cut a partial-chord length slot in the core 4"
    out, and insert the carry-through rib ?
    
    Terry

    I've been using the 3.17 oz./sq. yd. glass cloth from Aircraft
    Spruce with Saftey-Poxy made by Hexell (sp?).  So far, I've made 3
    "test" wing panels w/ 36" span and 10" chord.  The cores are cut
    from the free DEC "white" expanded bead foam using my automatic
    core cutter.

    My first panel used 2 layers of the 3.17 oz. cloth and was EXTREMELY
    strong.  Since then, I have cut it into four 9" sections to test
    some other building techniques.  Weight was 12 oz.  I think I used
    too much epoxy - the second and third panels look better.

    My second and third test panels were made with only one layer of the
    3.17 oz. cloth.  These panels are also very strong and I feel would
    be more than strong enough for actually flying.  They are also
    strong enough that you cannot dent them by just pressing on them
    with your finger.  Before the epoxy had fully cured (only about 8
    hours), I did dent the second panel with my fingers while removing
    it from the bag.  So, on the third one, I let it cure longer (about
    16 hours) before removing it from the bag.  No finger dents and a
    much nicer finish.  

    The second and third panels weighs 7 oz. each and I think I used
    exactly the correct amount of epoxy.  You have to remember that the
    foam is a little heavy too.  Somewhere else in this notes
    conference, Kay Fisher (I think) posted a list of how heavy the foam
    typically is...

    For the first panel, I used 20 inches of mecury vacuum and got a
    bumpy finish that looks similar to an orange peel due to the bumps
    and gaps in the expanded bead foam.  I was also using only 4 mil
    mylar (instead of 14 mil) because that's all I could find locally.

    Second and third panels used 8-10 inches of mecury vacuum w/ the
    same 4 mil mylar.  The surface is still bumpy.  I need to get some
    14 mil mylar.  I also will try using only 4-6 inches of vacuum and
    see if that helps.  I think the best solution may be to just switch
    to blue extruded foam.  The DEC foam was used for the test panels
    because I never intended flying with them and it was free.

    No spars in any of the panels.  For the "locals", I'll bring the
    panels to the next DECRCM meeting.

                       _____
                      |     \
                      |      \                          Silent POWER!
      _        ___________    _________   |            Happy Landings!
     | \      |           |  |         |  |
     |--------|-  SANYO  + ]-|  ASTRO  |--|              - Dan Miner
     |_/      |___________|  |_________|  |
                      |       /           |     " The Earth needs more OZONE,
                      |      /                       not Castor Oil!! "    
                      |_____/

    My concern is more along the lines of the higher aspect ratio glider
    wings. Long, slender, thin sections. I've been thinking of a layering
    similar to what Kay mentioned for his Lovesong (I think that was the
    context) where you use varying sized triangles from the root extending
    out the wings providing more rigidity towards the root. CF ribbon under
    the covering sounds like a good idea to me too.

re: Layers....  All layers of cloth are layed up in reverse order on the mylar
carrier....So put your 14 mil mylar down, put down some epoxy, spread it out,
put down the outside layer of glass, (say 2 oz), more epoxy, spread it out, put
down the next layer (say the 8oz uni-directional...oops in my last note on this
I said it was bi-directional, it was uni-directional), more epoxy, spread it out
then wrap this whole mess around the core and throw it in the bag!!  Presto

On the Carry through, it just a partial cut out of the core, if the core is
say 10" at the root, the carry through rib is 8", in other words leave 1-2" at
the TE and LE and put in the rest...Picture time....


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          ------------------------------------------------------------

I hate drawing these things.  The wat to cut them is to take some say 12 gauge
copper wire and put it in your Soldering gun and make it like a long U about
4-5" long and about 1/4" wide (or however wide you need it) then heat it up and
press it through the core and move it along to form the cut out.  Using the
end of this will also let you cut troughs for servo wires etc.

If this didnt come accross OK let me KNow...

RE: Note 1209.78 by NEURON::ANTRY
>>On the Carry through, it just a partial cut out of the core, if the core is
>>say 10" at the root, the carry through rib is 8",  [ ... ]

    Actually, I understood all of that because I've see a couple of
    videos (from the DECRCM library) that show this technique.

    What I can't figure out is this:  After the wing is glassed, how do
    you install (or locate) the tubes for the wing joiner rod?  

    I assume that the root rib has a hole drilled near the top and the
    carry through rib has a hole drilled near the bottom (depending on
    the amount of dihedral).

    Please elaborate on the process of connecting the 2 wings together.

                       _____
                      |     \
                      |      \                          Silent POWER!
      _        ___________    _________   |            Happy Landings!
     | \      |           |  |         |  |
     |--------|-  SANYO  + ]-|  ASTRO  |--|              - Dan Miner
     |_/      |___________|  |_________|  |
                      |       /           |     " The Earth needs more OZONE,
                      |      /                       not Castor Oil!! "    
                      |_____/

    I thought that the ribs and tubes would be in place when the core was
    bagged.
    
    I have a related question that was brought up by Al Ryder a while back
    (discussing Eindecker wing bagging). How do you prevent the root edge
    of the wing from "rounding over" due to the vacuum bagging pressure? I
    assume this isn't a problem due to the root rib being in place when
    bagged?

    The tubes and carry-through rib are in place before bagging. Everything
    should be trial fitted, aligned and permanently glued before bagging.
    As far as "rounding over", I've never seen this happen even with
    white foam. I put the root rib on after bagging as it is easier
    to make a precise flush fit with the skins, but there is no real
    reason you couldn't put it on before bagging.
    
    Terry

    Well, if the tubes are in place when bagging, then how do you
    prevent the tubes (and servo wire tubes) from filling up with excess
    epoxy?  

    Each answer brings another question...

                       _____
                      |     \
                      |      \                          Silent POWER!
      _        ___________    _________   |            Happy Landings!
     | \      |           |  |         |  |
     |--------|-  SANYO  + ]-|  ASTRO  |--|              - Dan Miner
     |_/      |___________|  |_________|  |
                      |       /           |     " The Earth needs more OZONE,
                      |      /                       not Castor Oil!! "    
                      |_____/

    There should only be a thin film of epoxy on the skins. Not nearly
    enough to be squeezed out the end and run down into the tubes.If
    that happens, then you've used way too much epoxy. Normally, the
    only indication of having a little too much epoxy is that it will
    be forced up through the pores in the wood and appear as brown stains
    on the surface. 
    The same applies when using multiple layers of glass cloth,except
    that you squeegee off the excess epoxy in between applying each
    layer. The glass cloth will retain more epoxy within its fibers
    of course, than a single sheet of balsa or obechi.
    A common technique when covering with cloth is to use a material
    called peel ply. This is a dacron (I think) cloth that goes on top
    of the outer layer of cloth. It soaks up any excess epoxy, then
    is peeled off after everthing is cured. It doesn't stick to the
    epoxy. I've never tried this technique, so can't say how smooth
    of a surface finish this gives. Mylar is still used on top of the
    peel ply.
    
    Terry

OK lets see here.

On the tubes and ribs.   Both root and carry through rib are in place before 
bagging, usually a hole is made in the root rib for the servo wire and its made
big enough so that you can get 3-4" of extra wire stuffed in it so you'll have 
some to work with.  Then I put masking tape of the edge of the root rib, the
side that would but up against the fuse, or the other wing.  Then you will not
have to worry about epoxy getting on the rib, or it filling in the servo wire
access hole, or crushing (rounding over) the edge of the foam, etc.  then after
you remove the wing from the bag, just sand all around the edge of the root rib
exposing all the way through the glass layer to the ply and then it will just
pop off and you are done.  

On the Tubes, I do mine after the wing is all done, you could go it before hand
but if you are doing the carry through/root rib way, versus the build a spar
box with the tube encased in it and all set with dihedreal etc. you dont have
much of a structure to work with, it will want to bend length wise as you try to
line it up and drill it, plus, like I said the less you handle the foam core 
itself the better.  So after the wing is bagged and you have removed the excess
from the root rib, the LE and the tip you can then lay your wing back in the
bottom bed and block it up to drill it.  Now drilling does not have to be a 
precise art you just dont want to poke the drill through the wing skin.  I just
have a piece of hardwood say, 2"x4"x2" that I have drilled some holes through 
using a drill press so that they are 90degres to the the block, then I clamp 
this block down on my bench and then jig the wing up to it.  Then for long drill
bits I just use brass tubing with some notches made in the end, it goes right
through foam and going through the two ply pieces, just takes a little bit 
longer.  Again, if it isnt what you want, and some of our guys dont worry about
that too much, they will purposly make the hole bigger than normal (but dont
poke through the bottom wing skin or you have violated the sturcture so to say)
then mix up some 5min epoxy and lay the tubes in and jig the wing up and let it
dry, then when that has set up they will mix some more 5min epoxy and warm it
up to make it viscous and then holding the wing upright pour the epoxy down
the hold surrounding the tube and filling it up.  Remember all you really need
is to anchor it to the root rib and the carry through, the glass skins do the 
rest.

    One other point to make about epoxy, the thin laminating epoxies
    such as Saf-T-Poxy, E-Z Lam, etc. will have a tendency to wick upward
    through the pores of the covering material rather than spread sideways
    looking for an escape route when vacuum pressure is applied.
    
    If you use the thicker slow cure construction epoxies such as Hobby
    Poxy II, they will try to ooze out sideways.
    
    Terry

re: .83 and peel ply, peel ply will not leave you with a smooth surface, it will
take on the surface of the peel ply.  The peel ply that I have seen had a 
texture like a burlap sack.  The mylar will leave you with a surface very 
similar to this tube that you are stareing at.  GLASSSSS SMOOOOOOTH....

On epoxy/glass wings, if you use more epoxy than glass by weight, something is
wrong.  Generaly when wondering how much epoxy to mix, weigh the cloth that
you will be using and then mix that much epoxy (by weight).

    That cloth weight = epoxy weight rule of thumb seems to be something I
    can remember easily.
    
    Terry, are you saying that Saf-T-Poxy or HobbyPoxy II is better or just
    different? I've been using HobbyPoxy II for my wood covered wings
    (weighted core bed method) but figured I needed different stuff for doing 
    the cloth versions.

    What Mark says about peel ply is what I suspected, but there is
    a fine weave version that is supposed to provide a smoother, but
    not glass smooth surface. Seems to me it would be simpler to just
    use less epoxy in the first place.
    
    On handling bare cores, I made up some cardboard sleeves that I
    keep the cores in before sheeting. I can slide the root end out to
    work on it , and the cardboard adds stiffness so that you can pick
    them up and move them around without worrying about breakage, dings,
    dropping x-acto knives on them etc. It is even possible for a cat
    to squat pensively atop them (but not for long) without damage.
    
    Terry

    re .87
    
    I'm saying that laminating epoxies such as Saf-T-Poxy are better
    for laminating purposes. They're thinner, spread out more easily,
    and are more economical.
    HobbyPoxy II can be used for laminating, as you and many others
    know, but once you try the laminating versions you'll see the
    difference. 
    
    Terry

    I'll go grab a fistful and give it a try P^)

    This past weekend I used my new Mighty-Mite vacuum pump from CST
    Technology for the first time on a 99" white foam/balsa wing.
    The pump is nice, quieter than an aquarium vacuum pump, and gets
    only warm to the touch after extended running. 
    The check valve, or something, holds the vacuum well when the pump
    is switched off, for several hours at a time, and I can't be sure
    that micro bag leaks weren't a contributing factor.
    I also used E-Z-LAM epoxy for the first time. It is clear, which
    makes it a little harder to see where your're spreading it, but
    it seems to flow out a little better than Saf-T-Poxy.
    With a room temperature of 65-75, night/day, it took 20+ hours to
    cure, so a heat lamp above the work bench will be an addition I'll
    use next time. The 2:1 resin/ hardener ratio is easier to measure
    than the 1:.44 ratio of Saf-T-Poxy.
    This would be good stuff to use for cloth over foam and adding color
    tint paste to the epoxy. I intend to do exactly that when I build
    the Ninja wings.
    
    Terry

    I'm about to dive into bagging and initially I'll be covering foam
    cores (with balsa leading and trailing edges) with glass cloth and
    epoxy on mylar sheets. I haven't looked for the mylar yet but most
    local people seem to be finding the 4mil stuff which can get wavy. My
    question is whether it would be beneficial to use a double layer to
    give more support between the core and the bag?

    
    	Reading the last reply an idea came into my mind.  A long while
    ago we used to buy a plastic skin material from Lanier.  The same
    plastic they use in their kits.  We were sheeting foam cores with it.
    This was when carbon fibre material hadn't hit the market so the
    wing often times came out weak so we abandoned the idea.  Could this
    plastic be used in place of the mylar. I think it would be thicker?
    
    Tom

    Hi Tom,
    
    Sig used to sell some stuff like that also. I think I have some rolled
    up in the shop still. I never really liked the stuff but bought it to
    give it a look. It is significantly stiffer and seems like it would
    work. My only other question would be, does the tranlucent quality of
    the mylar significantly help the positioning process?
    
    That brings up another question about this. One of the things I'm
    looking at initially attempting is a set of Panic wings. Now these have
    balsa leading and trailing edges. The trailing edge is pretty square so
    you can hinge the ailerons/flap onto the core. How does one use the
    mylar/plastic to do this type of wing? Do you cut the mylar to size so
    it doesn't hang over the trailing edge (and the more flexible bag can
    close around the TE)? Or do you make a normal airfoil and saw off the
    portion where the control surface goes and glue on a TE block? (I don't
    like this since I'm hoping to keep the glass intact for strength)

    With a wing structure like the Panic (God, I've typed the WORD!)
    I'd bag the core with the t.e. removed. Although if you had full
    chord cores, why not just cut out the aileron after bagging and
    use the cut out piece as the aileron ?
    I'm going to do the glass on foam bit with the Ninja but use the
    stock balsa ailerons since the cores are not full chord.
    
    I've bit the bullet and ordered the regular mylar sheet from CST
    Tech. It's more rigid and easier to handle than any cheaper substitutes
    I could find.
    
    Terry

    I've still got to make the Panic templates to cut the replacement
    cores. I can cut them with or without the trailing edge. Part of the
    flavor of the Panic is the non-tapered control surfaces which are
    supposed to improve the low speed sensitivity. Thus I'd be using balsa
    plank control surfaces. I didn't think the butt glued TE would be as
    strong and it would require me to further prep the wing (I was
    considering tinting the epoxy and stopping there)
    
    Keep me posted on how the Ninja wing comes out. I've considered
    building a wider wing since I'm heavier than I should be (the plane
    too 8^) and have used it off the high start for aerobatic practice when
    the wind is wrong.

    Saturday I played with the empty freon tanks I have and the
    compressor/pump. I picked up an automotive vacuum gauge (Honest honey,
    it isn't for the planes :^) and got the painting side working but found
    that the vacuum side bleeds the air back in with the pump off. Can
    someone suggest a place to look for a check valve that I could use? Can
    I get an aquarium one that will hold up? My pump is pulling 20 inches
    of vacuum with no problem (until I stop the pump).

RE: Note 1209.97 by ZENDIA::REITH
>>                            -< Check valve source? >-
>>    found that the vacuum side bleeds the air back in with the pump off.

    The pumps do indeed leak slowly through the vacuum side when they
    are shut off.  I found that this was not a problem after I set up my
    automatic on/off pressure switch.  With a 50 lb. Freon tank used as
    a storage tank, the pump only comes on every 6 to 8 minutes and only
    runs for about 30 seconds.  (Regulating between 8 and 10 in. Hg.)

    I had a heck of a time finding a check valve and finally gave up
    because the complete system works just fine as it is now.  My dad
    recommended a "Ball check valve".  Not a "ball valve" and not a
    "flap check valve".  But a "ball check valve".  I went to a few
    local automotive and plumbing places but they didn't have any.  One
    place even ordered a flap check valve for me but when to put it up
    to your mouth and blew through it backwards, it would leak.  More
    leakage than the pump itself.  Totally useless.

    Anyway, if you REALLY want a check valve, contact the large plumbing
    supply houses in Worcester.  (These places supply all the little
    local plumbing shops.)  Make sure you get a "ball check valve". As
    the name would imply, when you look in the end, there is a little
    ball that is free to move in one direction, but presses up against a
    round seat (stopping the flow) in the other direction.  I think some
    ball check valves also have a spring in then so that the ball is
    seated by default.  I planned on mounting it vertically so that
    gravity would tend to seat the ball.  (ie, pump would draw from the
    top; tank and bag connected to bottom.)

                       _____
                      |     \
                      |      \                          Silent POWER!
      _        ___________    _________   |            Happy Landings!
     | \      |           |  |         |  |
     |--------|-  SANYO  + ]-|  ASTRO  |--|              - Dan Miner
     |_/      |___________|  |_________|  |
                      |       /           |     " The Earth needs more OZONE,
                      |      /                       not Castor Oil!! "    
                      |_____/

    That's similar to the end of my rabbit's water bottle. Not sure if it
    would hold solid pressure for a long time. My pump seems to leak pretty
    fast. With just the gauge and 4 feet of tubing on it, it went from 20-0
    in about 10 seconds. crimping the tubing held the gauge pressure so the
    leak is on the pump side. The gauge does have a replacable bezel so I
    might use Al Ryder's circuit to set up the pump cutoff. My initial plan
    was to evacuate the bag and then clamp it off and make sure the seal is
    holding (double lines of caulk and a roller around the bag) similar to
    the hand pump and then check it manually a few times during the
    process. Hey, the initial "test" panels are just Panic cores P^)
    
    I was looking at the check valve to stop the backflow. I can do the
    same thing with a clamp and will probably go that way until I get a
    pump sensor switch set up.

RE: Note 1209.99 by ZENDIA::REITH 
>>    With just the gauge and 4 feet of tubing on it, it went from 20-0
>>    in about 10 seconds. 

    I get approx. the same results.  *BUT* if you include the storage
    tank in the circuit, you will see much different results.  That tank
    acts like a great big "vacuum capacitor".  Even so, you will need
    either a leak-proof check valve or a vacuum switch of some sort.

    BTW - I have some literature from a company that makes mechanical
    (diaphragm) vacuum switches.  I don't have any pricing info, but if
    someone feels energetic and wants to contact them, they are:

    Plant:  Stewart-Warner Hobbs Corp.
            Yale Boulevard & Ash Street
            Springfield, IL 62705

    Mail:   P.O. Box 19424
            Springfield, IL 62794-9242
            (217)753-7773   FAX: (217)753-7789

    Devices that seem appropriate for our use are:

        120007 (SPDT or SPST-NC or SPST-NO contacts available)
        M-4079 (NC contacts; M-4078 for NO contacts)

    These are rated at only 1 Amp @ 120 VAC so a relay would still be
    required.  These devices have their trip point set at the factory
    (to your requested pressure) and are apparently not user adjustable. 
    Also, the 120007 has a 0.4 to 1 in. Hg differential while the other
    does not.  If you get the M-40xx series, you may need 2 parts to get
    the proper differential required.  

    In other words, I would get a 120007 set at 9 inHg w/ a differential
    of 1 inHg.  If this range (1 inHg) wasn't enough, I'd get two M-4079
    set at 8 inHg and 10 inHg then wire them up with the relay to get
    the desired action.  (Yes, it can be easily done...)

                       _____
                      |     \
                      |      \                          Silent POWER!
      _        ___________    _________   |            Happy Landings!
     | \      |           |  |         |  |
     |--------|-  SANYO  + ]-|  ASTRO  |--|              - Dan Miner
     |_/      |___________|  |_________|  |
                      |       /           |     " The Earth needs more OZONE,
                      |      /                       not Castor Oil!! "    
                      |_____/

    I believe my check valve is made by the home aquarium line known as
    "Whisper".  It cost about $2 at a pet shop.  It consists of a rubber
    tube, round at one end and flat at the other and about 5/8th inch
    long.  The rubber is mounted inside a styrene can with 1/8th hose
    nipples at each end.  The complete device is 1 3/4 inch long and 1/2
    inch in diameter.

    Besides using it, I tested it.  I've discarded my documentation, but
    from memory I remember that the pressure half-life was on the order of
    many hours.  The potential leak sources for that test included, besides 
    the check valve, the tank, the gauge, and about 8 joints.  The external
    end of the check valve was open to the atmosphere.  The particular one
    used for the test was an old one taken from a working aquarium.

    Alton who just remembered that he didn't replace the "stolen" valve.

You know this is great all the info that flows around in here so freely....
Now if were all just located in the same geographical area.....

The one check valve that I have seen out here in Colorady came from a Welding
Supply company it is used in Oxy/Acetelene Welding hoses so that you dont
get flames going down the tubes back to the regulators, KABANG!!!!  Give
them a call and ask about their check valves.  Let me know if this is the right
stuff and what you find out.

    There's a welding shop on the trip home. If the aquarium version
    doesn't do it, I'll check there next.

    This months Model Airplane News has an article on Vacuum Bagging

    Is this the June subscription issue, the May newstand issue, or the
    April issue? 8^)

    It's the one I got yesterday in the mail.  Must make it the May edition.

    Well Randy (the REAL thing), I found the magazine and it's a good issue
    to pick up. They lay out the mylar method in great detail and have
    plenty of pictures. The sucker kit pump is similar to an automotive
    brake bleeding pump that they list for $25 (with NAPA number and name).
    The other article I found enlightening was the section on carbon fiber
    spars. I dread putting spars in my fiberglass covered foam wings. They
    gave a method for doing it with minimal hassle. Buy the CF ribbon and
    cut off a strip. With an Xacto knife and a straight edge cut a slot in
    the wing from root to tip. Glue the ribbon into the slot standing
    vertical. Repeat on other side for equal positive and negative G
    strength. This sounds like a great way to put in spars without digging
    channels. Minimal visibility in the covering and there is significan
    lateral strength in that ribbon (even if it IS expen$ive). I'll be
    trying this with my vacuum bagged glider wings in the near future. They
    also give a very good review of the Sig Ninja along with some shots of
    slope soaring down the Cape. The author had a 35 minute initial "trim"
    flight!

    Last night at our club meeting we saw a demo of the new Aerospace
    Composite Products vacuum bag sealing system.
    No more caulking, no more searching for pin hole leaks, no more
    having to cut the end of the bag off to remove the wing, and gradually
    losing bag length, no more having to caulk around the vacuum line.
    
    This will revolutionize bagging sealing methods. It's one of those
    "why didn't I think of that ?", things.
    
    I'm ordering mine this week. Naturally I forgot to ask the price
    but two 18" lengths of plastic tube and a valve stem can't be too
    expensive.
    
    Terry  

    Terry,
    
    You told us what you didn't have to do but you never told us HOW they
    did it.
    
    Ok, let's take a wild stab (yuck yuck, very punny) at it... it's a tube
    bag with an air hose nipple molded to the side that is zip locked at
    both ends?

    I had entered a detailed note earlier then lost the node, so reentered
    a condensed version.
    However, in order to escape further puns....you're description
    is fairly close to the concept.
    
    The vacuum line nipple isn't molded in but can be placed anywhere
    on the bag by cutting a small slit and sliding the top layer inbetween
    a rubber and nylon washer, then tightening a jam nut on the threaded
    portion of the stem.
    
    The end of the bag (tube type, nylon) is sealed with a full  width
    plastic tube cut to a C cross section. Both sides of the bag are
    placed down in the C, then a solid tube snaps in on top of the bag
    ends, trapping and sealing them. To release, you simply flex the
    outer tube, popping out the inner tube.
    
    Terry

>    The end of the bag (tube type, nylon) is sealed with a full  width
>    plastic tube cut to a C cross section. Both sides of the bag are
>    placed down in the C, then a solid tube snaps in on top of the bag
>    ends, trapping and sealing them. To release, you simply flex the
>    outer tube, popping out the inner tube.
    
    Let's see if I understand you...  The tube that is cut to a C cross
    section is the outer tube and the full tube is small enough to be
    snapped inside the other.  The bag material gets trapped between the
    2 tubes.  Is this right?



   (open end) bbbbbbbbbbbbbb   bbbbbbbbbbbbbbbbbbb (wing in bag here)
                           b   b
                         O b   b  O           b - bag material
                       O b  III  b O          I - inner full tube
                      O b  I   I  b O         O - outer "C" cross section tube
                       O b  III  b O
                        O bbbbbbb O
                         OOOOOOOOO


                       _____
                      |     \
                      |      \                          Silent POWER!
      _        ___________    _________   |            Happy Landings!
     | \      |           |  |         |  |
     |--------|-  SANYO  + ]-|  ASTRO  |--|              - Dan Miner
     |_/      |___________|  |_________|  |
                      |       /           |     " The Earth needs more OZONE,
                      |      /                       not Castor Oil!! "    
                      |_____/

    Yep Dan, you've got the concept right. I don't quite understand
    what the bottom row of O's are in your diagram, but the inner tube
    nestles inside the C section tube and is visible through the open
    side of the C. When the vacuum hits it, everything is pulled tight,
    and no leaks !
    
    Terry 

    re .111
    
    Looked at your diagram again. Yes, it's exactly correct.
    
    The valve stem is fluted so the the vacuum line is just pushed on
    over it. No clamps needed. The valve stem is a precision machined,
    high quality item. Looks like it might have an aerospace application
    in a pneumatic system or something.

    I read in Model Aviation (Soaring col) that an old bicycle tube stem
    works good for this too.  Of course, you may need a clamp and/or
    the vacuum line that fits snugly over the stem...

                       _____
                      |     \
                      |      \                          Silent POWER!
      _        ___________    _________   |            Happy Landings!
     | \      |           |  |         |  |
     |--------|-  SANYO  + ]-|  ASTRO  |--|              - Dan Miner
     |_/      |___________|  |_________|  |
                      |       /           |     " The Earth needs more OZONE,
                      |      /                       not Castor Oil!! "    
                      |_____/

    Sounds like a workable system. I might try the nipple through the flat
    bag trick anyway since most of the edge leaks seem to be around the
    vacuum line. I've seen potato chip bag closures that were similar to
    this design. The only problem I see with it is that you still need to
    slide the goopy wing into the bag from the end rather than making the
    bag around the core.
    
    A threaded fitting with ridges and a couple of faucet washers with
    metal washers on the very outside should seal pretty well. I think I'll
    give this a test (without epoxy) to try it out. I saw usable fittings
    at the hardware store when I was plumbing my freon tank setup.
    
    Losing the connection:
    
    I've done this a couple of times when I've got a long note to enter.
    You can create a file with the note text in your favorite editor and
    then copy it over to your notes node (I use Ultrix on the current
    project but have a VMS node for notes) and then do a "reply filename"
    and it will insert your text as the note body.

    Jim, 
    
    I'll do the reply file name trick next time I have a long note.
    
    Regarding the "goopy" wing into the bag trick, what I do is lay
    down a paper towel slightly longer than the core then an equal length
    piece of wax paper on top of that, then the core on top of the wax
    paper. Run a short length of masking tape from under the paper towel
    up over the end of the core. This secures the ends so they don't
    flop around as you slid the whole mess into the bag. The paper towel
    acts as a vacuum wick also. Just make sure it isn't long enough
    to get sucked up against the ends of the core unless you enjoy peeling
    it off bit by bit later.
    
     Terry

re ELMAGO::TTOMBAUGH  < New ACP vacuum bag sealing system >-

>>  no more having to cut the end of the bag off to remove the wing, 

    I don't understand the problem --- because we don't have it.


    We use the very soft, compliant, and sticky caulk tape for two edges
    and around the air line.  This tape is Frost King Fingertip Wedge
    Caulk.  It is so sticky that we don't try to remove it.

    We use the cheap, putty-like rope caulk for one end; that end can be
    opened with a sudden snatch (like Silly Putty) and resealed weeks
    later.  It is resealed in seconds with no fuss or corrections.  This
    tape is DAP Weatherstrip Caulk.  

    I have used two bags about six times and two bags seven times. Only
    once did one bag need to be cut; I forgot why, but it wasn't a leak.
    Although the bags are beginning to look like floor mats in the football
    locker room, there are no detectable leaks.  When I bagged my Chup
    wings recently, the pump ran a total of 9 minutes, twenty seconds in a
    twenty hour period with two bags on the system.  [There is a clock in
    parallel with the pump.]

    I have problems (another note topic), but seals are not amongst them.
    I do have the advantage of an automatic pump system; otherwise I would
    have had to pump every forty minutes or so.


>>  a valve stem 

    I saw the review in RCSD, but I really don't see the problem being
    solved on this one either; the soft, sticky caulk need be put around
    the line only once and left there.  

    Incidentally, I had to draw vacuum in my kitchen and take the bags
    upstairs to cure (no flat surfaces upstairs in an old farmhouse).  
    So I put a Whisper [aquarium] check valve on each bag.  The vacuum 
    held for the transfer.  [The only other check valve on the system is
    also a Whisper, a two dollar item.]

    Alton, who also dislikes stuffing a sticky wing into a narrow bag

    As I said, I do have some problems.  Unlike the Eindecker's, the Chup
    wings are tapered and undercambered.  The damn cores slithered in the
    balsa sandwich, and the sheeted wings were almost impossible to keep
    aligned in the beds.

    Before painting on the epoxy I taped the trailing edges of the sheeting
    together with a gap.  After spreading the epoxy, the balsa was scraped
    dry.  The core was put down on one side, the other sheet was pulled up
    and over the core, and the sandwich was held in one hand while being
    slid into the bag.  The bag-with-sandwich was put into the beds, and
    manual pressure was applied to the beds by my wife while the bags were
    resealed and vacuum drawn.  I noticed that with a tapered and
    undercambered wing, misalignment in any direction can be more serious
    than misalignment of a semi-symmetrical, straight wing.
    
    This is no way to run a railroad.

>         <<< Note 1209.110 by ELMAGO::TTOMBAUGH "A Fistful of Epoxy" >>>
>                         -< More bag sealing details >-
...
>    The vacuum line nipple isn't molded in but can be placed anywhere
>    on the bag by cutting a small slit and sliding the top layer inbetween
>    a rubber and nylon washer, then tightening a jam nut on the threaded
>    portion of the stem.
>    
>    The end of the bag (tube type, nylon) is sealed with a full  width
>    plastic tube cut to a C cross section. Both sides of the bag are
>    placed down in the C, then a solid tube snaps in on top of the bag
>    ends, trapping and sealing them. To release, you simply flex the
>    outer tube, popping out the inner tube.
    
Terry I read the above several times and stared at Dan's drawing and
I'm totally lost.

Could you (or someone good at drawing terminal pictures who understands
this) please make a good three view?

You said there were two 18 inch tubes.  Open on both ends?
Each the same size?  18 is so small - the real bag must be
the 7 feet of 18" tube - right?  Two 18 inch ends can't cover
one 7 foot long piece so how does this stop pin hole leaks?

Help?

Bye          --+--
Kay R. Fisher  |
---------------O---------------
################################################################################

    One more time. This is your brain being vacuum bagged......
    
    Dan's cross section picture really says it all. If anyone can improve
    on it have at it.
    
    The bag is of course the tube type, so only two edges need be sealed.
    The ~18" tube length is just long enough that the bag width fits
    inside the outer tube length, which has open ends. This doesn't
    affect the sealing properties because the bag is lapped/rolled,
    in and over the tubes and when the vacuum hits it the tubes are
    pulled down tight enough to prevent leaks.
    
    Alton is lucky enough to have caulking that can be reused. I've
    never seensuch stuff. I've tried 3M, Manco, and some other brand
    I don't remember the name of. Once they are stuck, that's it, the
    bag rips before they release. But I dislike installing the tape
    and rolling it out, so anything that eliminates that step is worth
    it to me.
    
    On the other hand, putting the wing in the bag doesn't bother me
    because I tape the cores in place on the ends, and tape the wax
    paper, paper towel in place so that nothing can slide around while
    handling. I've tried using the core beds while pulling the vacuum
    but abandoned the practice because it didn't seem to make any
    difference.
    Now I hold the core upside down in the top bed half only until the
    vacuum is established,then take it off and lay it right side up
    on the bench. The t.e. of the wing is positioned close to the edge
    of the bag so that I can clamp the t.e. between two long pine strips
    with clothes pins. The whole thing is then positioned along the
    edge of the bench in such a way as to prevent any up or down tension
    on the t.e. caused by the strips or clothes pins.
    Sometimes I use the bottom core bed as a spacer in this operation,
    but don't use the top bed or any weights on the wing.
              
    Terry

    Terry,
    
    	To explain what your doing differently...
    
     1) One end of the bag is perminantly sealed and has a nipple of
    	some type installed.  This nipple is where the vacuum pump is
    	connected.
    
    2)  The closure for the other end consists of a tube with a small
    	cross section removed to create an end view that looks like a C.
    
    3)	The open end of the bag is draped over the open section of the
    	tube. Ie,
    
    		bbbbbbbbbbbb <-------------bag
    		   c   c
    		    c c   <----------------tube
    
    4)  To this another tube is added.  the second tube fits into the
    	inner diameter of the of the first C tube.  This effectively
    	pinches the bag closed.
    
    
    
    
    Tom

    I see the problem that Kay is having. I just had it with the
    reexplanation in .-1
    
    The 18" tube is the clamp for the end, not the bag.
    
    The bag is of the "tube type" (but referred to as "bag")
    
    The clamp is two concentric "tubes" with one having a slit in it and
    the bag is wrapped around the inner tube and then the outer tube is
    snapped on over it to make the seal (refer back to Dan's pretty
    picture).
    
    18" is the width of the bag. The size of the opening and the size of
    the clamp. I didn't see the bag length stated anywhere.
    
    This is your brain, this is your brain after leaving the battery switch
    on overnight. Any questions?

    .122 is referring back to .120

    I found a source for vacuum bags/tubes over the weekend. The woman my
    family went to visit on sunday makes curtains. While my wife was
    looking at stuff that I'm sure will end up costing me $5 per inch, I
    was looking at the plastic bag they came out of. She gave me a catalog
    of the source. The catalog is from 1/1/90 so the prices might have
    changed.
    
    R.H. Rowley Company		Office hours 8:00am-5:30pm (eastern time)
    230 Meeks Road		1-800-343-4542 (US and Canada)
    Gastonia, NC 28054          Fax 1-704-868-9787
    				local and others 1-704-866-0650
    
    Orders in before 3:00 eastern time are shipped the same day. Stock is
    maintained on all items. Master Charge & Visa. Minimum order $15.
    Shipping charges are by weight.
    
    Plastic tubing by the roll
    
    Stock #	Description
    PET 6	6" wide 1 1/4 mil. thick - 160'/lb
    PET 7	7" wide 4 mil. thick - 44'/lb
    PET 13	13" wide 1 1/4 mil. thick - 75'/lb
    PET 24	24" wide 2 mil. thick - 25'/lb
    PET 30	30" wide 2 mil. thick - 20'/lb
    
    All sizes in rolls that vary from 20 to 30 lbs.
    single rolls	$1.76 per lb.
    100 lbs.		$1.68 per lb.
    500 lbs		$1.52 per lb.
    
    Poly bag for shipping fabric
    
    6 mil. 12" wide 72" long (shipping weight approx 1/3 lb. per bag)
    PET 50	10 bags	$.95ea.	50 bags	$.85ea.	100 bags $.75 ea.
    
    Personally, I'm interested in a roll of the 2 mil. 24" stuff and 10 of
    the bags at the bottom to check them out.
    
    Standard disclaimer: I have no interest in this company. Just passing
    on a possible (unusual) source for materials

    Charlie Watt had mentioned that he was using Envirotex epoxy from one
    of the local lumber yards successfully. I stopped on my way home last
    night and had some trouble getting my point across to the clerk(s) when
    I called it epoxy. They use it as a two part bar and table top finish.
    Take out the instructions and they warn about epoxy resins. The word
    epoxy appears no where on the outside of the box. The full brand name
    was Envirotex Lite and it cures in 8 hours and fully hardens in 72. It
    has a working time of about 20 minutes. I'll report back as soon as I
    bag my wings (hopefully saturday)
    
    16oz for $11 and it mixes 1:1. Looks great now that I know what to ask
    for.

    I've got one more question for the experienced folks out there. What do
    people think about adding the aileron LE/Wing hinge spar BEFORE
    bagging? I was thinking of putting both of these in place and running
    scotch tape down the joint to be separated after the fact with an
    Xacto knife. I just think that this would be a better seal to the skins
    if it was done before rather than cutting and retrofitting it after
    the wing is bagged. Has anyone tried this? I'm considering doing this
    on a wing that I'll use the mylar and glass cloth method.

    Jim, 
    I'm not sure if I follow you entirely, but if you mean to glue the
    wing t.e. in place, the strip that butts against the aileron l.e.,
    before bagging, then that works fine. I've done it several times;
    just shape and sand the t.e. strip and glass or sheet right over
    it.
    I don't understand the part about the scotch tape.
    
    Terry

    Jim,
    	I've also thought about it but was going to take it a bit further
    that being shaping the LE piece of balsa for the aileron and adding
    the side caps.  I did a process flow as follows (Process engineering!!)
    
    1) Cut slot in core to fit TE of the wing cut out and LE of aileron
    2) Carve and sand balsa TE/LE to the shape of the wing.
    3) Glue TE and then LE to foam.
    4) Cut out aileron from core and face aileron and cut out with 1/16
       balsa.
    5) Cut bevel into LE of aileron.
    
    Reinstall aileorn and sheet cores. I'd considered sheeting with 1/16
    balsa so wasn't really worried about any epoxy flowing into the TE/LE
    joint.  I guess a peice of tape could be used to mask off this joint.
    Then it would be a simple task to cut the aileron out of the sheeted
    cores.
    
    
    Tom

    
    Terry,
    
    He's considering having both the TE of the cut-out and the LE of
    the aileron in place in the core prior to the sheeting.  This would
    require the tape to seal off the joint.
    
    Thinking about the process flow it would be necessary to cover the
    facing sides with tape also to keep glue from seeping down into
    that joint.  Another idea would be to sheet only one side of the 
    wing panel.  Then cut a slot through this sheeting along the facing
    pieces. Then sheet the other panel.  If the cuts were done very
    accurately it would define where the TE/LE joint was and make the
    cutting process of the sheeting that much easier.
    
    
    Tom

    Sorry, I went flying 8^)
    
    Tom's got the idea. The core has a wood leading edge but the TE is just
    glass with some CF laminate in between. The ailerons are just a section
    of this trailing edge. The only covering is fiberglass. No sheeting.
    There were two ways I was considering doing it.
    
    The first way (which I've talked myself out of but...) is to cut out the
    aileron hinge area and insert a solid piece of balsa and glue the
    aileron back on. After covering, you cut out the aileron and put in the
    final bevel.
    
    The second way is what I described. cut out the aileron and add the
    balsa leading edge and the trailing edge cap to the raw wing. Put
    scotch tape on the hinge surfaces between the aileron and wing so they
    don't get stuck back together. Then I figured on sticking them back on
    with double sided tape (against the two scotch tape surfaces) and
    bagging the wing as one piece.
    
    So I guess I'll reask the question a little differently. Assuming Terry
    is saying that imbedding the wood in the core before bagging is ok, am
    I better off leaving the aileron attached with a solid piece of wood
    and cutting the piece of wood in half to free the aileron afterwards or 
    cutting it free and tacking it back in place for bagging?

    I get the picture now. 
    It's best to do the bagging with all parts of the wing intact and
    attached. The sheeting, cloth, etc. can then follow the airfoil
    shape more closely.
    
    Do I understand that you're considering cutting the ailerons out
    of the foam first, facing them, reattaching them, then bagging the
    whole thing ? What advantage do you gain by this ?
    Is this easier than bagging first, then cutting out the ailerons?
    
    The control surfaces can be cut free even if the core is covered
    only with glass. It just takes a good straight edge held steady
    and a sharp blade. Taking care not to dent the surface would be
    the biggest concern.
    
    Terry

    Well, you've got the general idea now. The intent was to have the
    ailerons cut free from the wing already faced with the facing glued
    properly with/to the skin, not attached after the fact with the foam 
    hollowed out from the facing area. I figured I could cut the ailerons
    out of the bare core and face them easier than bagging the wing and
    then trying to dig out for the facing to fit in place (I get the
    picture of thousands of little foam beads sticking to everything) I
    think I've talked myself into using a solid piece as the facing and
    then subdividing it after the bagging is all done.

Well - consider this - the AHS (Aileron Hinge Spar (I gave it a name))
will have to be beveled after you come out of the bag which will certainly
end up having you sand a little into the top part and fighting to get
a good match with the aileron leading edge against the wing.

Sooooooo - make the AHS one piece and cut it free.  This will save you
the grief of having epoxy forced down between each side of the scotch
tape and making a real mess.

Besides - that is the way Dodgson says to do it!

Bye          --+--
Kay R. Fisher  |
---------------O---------------
################################################################################

    Just what we need another TLA - Three Letter Acronym!
    
    Well I hadn't seen it anywhere but thought it might be a useful method.
    Thanks for the industrial confirmation.

    After investigating Frank Weston's new electeric designs, I am back
    to an issue I have been avoiding for at least a year now - VACUUM
    BAGGING!!!!  I will admit that I have been afraid to tackle this
    facet of building mostly due to expense and the fear of failure(ie
    messing around and paying my dues by making mistakes).  I know some
    of you have done or are currently doing vacuum bagging.  Obviously
    the wrong way to learn is on a beautiful set of purchased cores.
    I guess due to the limited building time I have, I have not wanted
    to waste time "practicing" a new building technique.  IS vacuum bagging
    hard to do well?  Are there any sources who will make custom bagged
    wings, if so any cost estimates?  
    
                                                        Thanks,
    
                                                        Jim

    There's a vacuum bagging topic in here somewhere. My personal feeling
    is that first you want to learn foam cutting. Once you have a method
    for turning out reproducible foam cores, you can afford to screw
    up, crash, or wing fold an initial attempt or two. My suggestion to
    someone buying a set of expensive cores would be to reverse engineer
    them to templates and practice on a personally cut set. This also gives
    you a backup set if they come out well. Just like anything, practice
    makes perfect. I cut a large number of Eindecker wings and learned a
    LOT about cutting foam. I built one of the single wire automatic foam
    cutters and it took a while to get all the pieces working right. At
    $5-$7 for a 2"x2'x8' chunk of foam, you can cut lots of foam cores in
    order to get a couple of reasonable ones. I'm stalled right now on
    actually getting down and dirty and mixing the epoxy to bag my first
    personal set (most of the cores were for other people who were happy
    to give me the "practice"). I've tried the stacked method for attaching
    skins with epoxy and F77 contact adhesive and I think bagging will be
    the easiest. The local results I've seen tells me that this is the way
    to go for the easiest/strongest wings. But like everything else, the
    first time is the most stressful. My advice is that you don't want to
    be buying the raw cores each time you try bagging. You want the piece
    of mind that you can toss a mistake set and try again  tomorrow night
    by spending a half hour cutting another set of cores from the same
    templates. Besides, maybe you want a 2-meter set and a standard class
    set for the same fuselage. Just cut longer cores and go for it.

>   <<< Note 399.950 by ZENDIA::REITH "Jim Reith DTN 226-6102 - LTN2-1/F02" >>>
...
>    There's a vacuum bagging topic in here somewhere. My personal feeling
>    is that first you want to learn foam cutting. Once you have a method
>    for turning out reproducible foam cores, you can afford to screw
>    up, crash, or wing fold an initial attempt or two. My suggestion to

Well - maybe.  Jim and I usually agree on these kinda things but you have to
admit most kits come with foam wings not templates.  So it only makes since
to me to bag first - after all that's how you put your kits together.

Then later when you think you can design a more optimal airfoil to go
with your sailplane than the designer you can start cutting cores :-)

Welllllllll

Anyway - if you have a kit with foam cores and you have never bagged before
and you want to - get the simple combined pump/regulator from 
(who was that Aerospace Composite Products or somebody else??) and
follow their instructions.  No - they won't be perfect but then neither
was your first Monokote job or your first CA glue joint or...

On the other hand if your scratch building - then by all means cut first.

Remember bagging is just a fancy way of attaching sheeting to foam.
You can always just sandwich the cores and covering in the wing saddles
and put weight on top.  Works fine, lasts a long time, doesn't rust,
bust, or collect dust!

Bye          --+--
Kay R. Fisher  |
---------------O---------------
################################################################################

    Kay, you're right that it's easy to weight the cores if you are
    using balsa (or other wood) sheeting, but I think Mr. Blum (Jim ?)
    is referring to using fiberglass to cover wings with no wood.

    In that case, vacuum bagging is (almost) the only way to do a good
    job.  I would recommend getting a good videotape (or borrow the ones
    from the DECRCM video library if Kay isn't too busy) and watch how
    it's done.  It's really VERY easy.  I did a few practice cores first
    and was _REALLY_ impressed with how easy it really was.  Sure they
    weren't perfect, but I easily learned what I did wrong:  
        1) I used too much vacuum (I used 15-19 inches of mecury) 
            - 5-8 is good for white foam
            - 10-12 (?) is good for blue foam (Note: your milage may vary)
        2) I used el-cheapo thin (4 mil) mylar instead of the 14 mil
            mylar that was recommended.  Spend the $ to get some good 
            14 mil mylar (Weston and others carry this).

    Weston Aerodesign has a video that I'd like to buy on how to build a
    Magic.  It is really more a video of "how to do composite glider
    construction" than an assembly process for the Magic.  Disclaimer: I
    haven't seen this video yet, and the above comments are based solely
    on the description in the catalog.  But - it sounds like a good
    video.

    Go ahead - give it a try!  You too will be amazed at how easy it
    really is.  I second Jim Reith's suggestion to cut some sample cores
    that are not longer than 36" to start with (easier to handle and
    wastes less practice materials) and try bagging them.  Before you
    start, take the attitude that you are going to throw them away when
    you're done and you'll be free to go ahead and make those first one
    or two mistakes.  Then it's smooth sailin'  :-)  (Don't make the 90"
    wings that cost $200. your first project...)

                       _____
                      |     \
                      |      \                          Silent POWER!
      _        ___________    _________   |            Happy Landings!
     | \      |           |  |         |  |
     |--------|-  SANYO  + ]-|  ASTRO  |--|              - Dan Miner
     |_/      |___________|  |_________|  |
                      |       /           |     " The Earth needs more OZONE,
                      |      /                       not Castor Oil!! "    
                      |_____/

    By the way, the FIRST time I bagged a wing it only took me 4-5 hours
    and that included 2-3 hours of running around setting up the
    workshop, doing a couple of "dry" runs to make sure everything would
    work OK, etc.

    Last week, I bagged a whole 48" wing for my Gremlin (power combat
    plane) and it only took me 2 hours: 1 hour to set up the workshop
    (garage) and one hour to layup the glass and get it in the bag. 
    Since the workshop is still "set up" I could do another one in an
    hour.

    Vacuum bagging is by far the quickest, easiest, strongest, and
    usually the cheapest way to make a wing.

            "Just DO IT!"

                       _____
                      |     \
                      |      \                          Silent POWER!
      _        ___________    _________   |            Happy Landings!
     | \      |           |  |         |  |
     |--------|-  SANYO  + ]-|  ASTRO  |--|              - Dan Miner
     |_/      |___________|  |_________|  |
                      |       /           |     " The Earth needs more OZONE,
                      |      /                       not Castor Oil!! "    
                      |_____/

    Last few from Dan:
    
    That's what I need to hear so I can get out there and do my Chup wings.
    I've been dragging my feet through fear of not succeeding. Time to go
    out and do it to it.
    
    Kay:
    
    My comment was more to take the expensive cores and draw around the
    ends. This gives you the start on a template and you can go from there.
    I was trying to promote something useful from the test cores (backup
    wings). Doing 2' symetrical sections like Dan Miner did is great for
    learning technique (and I hope to be ahead by following his advice from
    his experiments) but isn't terribly useful to an electric/glider
    person. My first attempt will probably be a set of Panic wing cores
    followed by the Chup cores and then the stiffer Cloud Bound 99
    replacement wings. I hope to learn more in each session and the Panic
    cores will be non-critical. I'll weigh and balance each set before and
    after to check my progress/technique.
    
    As Dan Miner mentioned, I'll be using 3oz fiberglass over foam with no
    sheeting in all these cases and I'm using carbon fiber laminate as
    spars. Personally, I'm not convinced that vacuum bagging buys you much
    over simply weighting the cores in the wing saddles for putting
    sheeting/obechi on. I feel it wins big in the mylar style ready for paint 
    method of putting fiberglass directly onto the foam.

re Note 1209.135 by USRCV1::BLUMJ    -< Vacuum Bagging >-

>>  Are there any sources who will make custom bagged wings, 

Yes.  Wing Manufacturing comes to mind.  Let us know what prices you are
quoted and what the price included.

>>  Is vacuum bagging hard to do well?  

I think not.  I learned by doing two dozen Eindecker wings, only one of
which was trashed.  With that exception, the others improved in quality 
as I learned.  The Chup wing was much harder because of the complex shape. 
I still have a lot to learn, but I've earned my apprentice rating.

>>  to waste time "practicing" a new building technique.  

If you are to learn, you will indeed practice.  It is only a question of 
how much the practice materials cost.

I'm intrigued by the notes about foam cutting and bagging. With all the
emphasis on practice, I'd like to get some practice without the hassle. If
anyone plans to cut a number of wings (such as our illustrious Gremlin kit
makers) or bag some wings, I'd like to watch over your shoulder (and be
available to help if you want some inexperienced help).  In case there are any
other people that would like to learn by watching (and asking questions),
please post a note if you expect to do any significant amount of cutting or
bagging and won't mind some "help".	Thanks /egp

P.S. I live close to the CMRCM field, so I'd be interested in going anywhere
within about a half hour of the CMRCM field.

    I'm out in Southbridge, west of Worcester but I'd be willing to have
    onlookers. My big problem is that most of my work is catch as catch can
    and I don't always KNOW when I'll have the time to cut some cores. I've
    got to cut a set of Panic wings and a set of glider wings before I get
    serious about practicing bagging but my cutter is sitting on the floor
    (normally wall mounted) right now due to some unexpected remodelling.
    Send me mail if you'd like to sit in on a rainy saturday session at my
    house in a few weeks and I'll let people know in advance by email.
    Lawton Read and Kay Fisher sounded interested in the past, we can
    probably get a whole crew going. If one of the experienced vacuum
    baggers is interested in joining us, I'd be willing to supply cores and
    materials for a bagging demo (I've got projects backing up waiting for
    me to do this). Maybe early September for a full day session? (time to
    break it to my wife and clean 8^)
    
    Bring your templates and foam and head home with some cores... (what am
    I setting myself up for? 8^)

    The way I broke into foam core sheeting/vacuum bagging, was to first
    do a couple of wings using WATER BASED contact cement to apply the
    sheeting. This gave me practice in trimming, best amount of overlap,
    etc.
    Then when I started vacuum bagging with epoxy, the only significant
    difference was the bagging process itself.
    I've never screwed up a wing, aside from having to retrim and reglue
    some sheeting for wrong sizing.
    
    On a related subject, Taylor Collins was showing me some sample
    panels of two layers of 3 oz. cloth over foam.
    He got the color in the layup, by spraying (white) the bottom of
    the mylar sheet with a coat of auto vinyl top refinishing paint,
    available in auto supply stores in spray cans.
    
    In the bagging process, the paint transferred from the mylar to
    the surface of the cloth, nice and even, no voids or rips, when
    he peeled off the mylar. The finish is as good as a spray-on job
    but the paint is flat, not glossy. If you can live with that, this
    looks like a surprisingly effective way to get a color coat on a
    cloth layup.
    
    Terry

    Terry,
    
    Maybe I'm missing something but where is the benefit of spraying the
    mylar rather than the finished wings? I've also heard of people
    pigmenting the epoxy but haven't heard/found what pigments they're
    using.
    
    I assume your WATER BASED contact cement comment was to avoid stuff
    that disolves foam.
    
    On a humorous thought, how about clear epoxy over a nice Tartin plaid??

    I guess the benefit is that no surface prep of the wing is necessary
    and you're all done when the wing comes out of the bag.
    
    I've used the West System white pigment to tint the epoxy,several
    times, but it doesn't really give a good color, a slight milky
    appearance at best. There isn't  enough depth to a cloth finish
    to give enough area to hide the core no matter what type of mixed-in
    paste you're using. I'd think that at least a 50/50 ratio of tint
    to epoxy would be required before anything could be seen, and that
    ratio is far beyond what they recommend and would probably mess
    up the epoxy binding qualities.
    
    Terry

    Al Casey always said that if you learn something, pass it on.
    
    In note 1209.59, Al Ryder presented a switch circuit to turn on and off
    a vacuum pump for hands off bagging. I built it this weekend and it
    worked first time. Here's the Radio Shack part numbers I used and some
    changes I made. Total cost was under $20 (minus the vacuum gauge)
    
    Radio Shack didn't have a 555 in stock so I used a 556 which is two of
    them in the same case. 276-1728 @$1.49
    
    I used cheap zener diodes (1N34A) since they came 10 to a package. 276-1123 
    @$.99
    
    2 1K ohm 1/2 watt resistors were $.25
    
    The relay I used was 275-206 which is a DPDT 3 amp 12vdc relay (with
    socket) $5.99
    
    276-1999 was the 14 pin socket for the 556 @$.89, 275-1547 was a 4 pack
    of momentary push button switches @$2.69, and 276-149 was a small
    indexed PC board @$.99
    
    I went to a 12vdc relay since I have 12vdc power supplies and figured I
    could use my flight box to power it (worked fine). I bought a standard
    120vac duplex outlet and a light switch to allow me to plug in the
    vacuum pump (and a cheap electric clock to check pump run time) and the
    switch acts as an AC kill switch. The momentary switches were placed
    across the two sense lines and are used for manual on start and stop
    switches. The vacuum gauge I have has a replaceable bezel which screws
    on. It is a thick plastic and I drilled it out and put a small piece of
    brass tubing in the hole to support the wires that come in contact with
    the pointer. My method of starting the procedure was to put in the
    reset sense wire at the maximum vacuum mark and press the momentary
    contact switch (across the trigger sense line) to start the pump. When 
    the pump reaches pressure and turns off, I placed the trigger sense
    wire into the minimum vacuum hole. Now as the pressure bleeds to that
    point the pump is restarted. The relay is socketed (provided in the
    part number specified) and is available separately as a replacement.
    
    I'm intending to put mine in a small box to keep prying hands away from
    the AC line voltage. The 556 circuit can take up to 16 vdc input and
    the diodes specified are 15vdc so the flight box battery is fine and
    will run it easily for the 24 hours some baggings require.
    
    The wires through the gauge bezel are kludgy, but it wouldn't be fun
    otherwise and they give a positive visual reference as to the pressure
    range you're using. I thought the manual start, stop and kill switches
    were useful and the use of the standard outlets requires no
    modification of the pump for wiring. I used standard large aquarium
    tubing for the vacuum lines and air-line check valves on each bag line.
    Unused lines have the check valve reversed to act as a plug.
    
    A tube of chalk and some bagging material and I should bag my first
    wing sometime this week.

    Well, Bob provided me with a good excuse to try vacuum bagging. My
    experience wasn't totally good or bad. I used clear acetate sheets as
    the mylar in my method since I was unable to get any myular on short
    notice. I used what was called a heavy duty drop cloth and mortite
    caulk to make the bags. Turned out the drop cloth was only 1.9 mil and
    leaked (pinholes not edges) Next time I'll use at least 4 mil. I used 3
    oz glass and the new HobbyPoxy Smooth and Easy epoxy. The rule of thumb
    I had heard of the same number of fluid ounces as ounces of cloth used
    proved true. The acetate sheets wouldn't stay flat on the leading edge
    so I ended up weighting down the core beds outside the bag. I used
    disposable latex gloves and this saved me on cleanup. I checked it this
    morning and the core came out well with some leading edge and wingtip
    gaps. The surface is like glass and the acetate released easily. Next
    time I'll use heavier bag material and a wider band of flexible
    material at the leading edge.

    Well, I have all sorts of cores to cover now that I built my foam
    cutter...  So I read through all of this...
    
    RE: clamps for the end of the bag.  I have found that these can easily
    be made from 1/2" CPVC and 3/4" PVC Sched 40...  Simply rip the 3/4"
    PVC lengthwise, turning the sideview "O" into a "C".  Smooth the edges.
    Depending on how much you cut off, you can vary how tight the clamp
    will be.  Now, wrap the end of the bag around the 1/2" CPVC and push
    the "C" clamp over the top.  It looks like it will work nicely.
    
    RE: Bags..  The fish stores come to the rescue again!  They have 
    plastic bags of varying sizes for sending home fish.  The couple of
    clean ones I have fit nicely around the predator wings I cut.  They
    come larger as well.
    
    RE: Glues...  I haven't tried it yet, but no one has mentioned using 
    3M F-77 spray contact cement.  Has anyone tried it??  Steve Schomer
    uses it and claims good results.  You still bag the wings to insure 
    good adhesion.
    
    I have a Dan Miner special pump, and an Al Ryder (Jim Reith parts list)
    switch.  I'll be using a 5 gal tank from an expendable Helium tank,
    and aqarium tubing, check valves and "t"s.
    
    Thanks for all the good notes!
    jeff
    

    The aquarium hardware works fine. The 5# tank sounds small for the
    reservoir. I've got a 20# and 50# freon tank in mine. I just reverse
    everything and use it as a spray compressor also. I'd be interested in
    seeing you clamps sometime (the 4/5 contest?) Those and the carpet
    or fish bags sounds like a reasonable setup.

    The 3M 77 spray contact cement works ok, but I like brush-on Elmers
    water based contact cement better. I think you can put on a lighter,
    thinner coat and it's less messy and cheaper.
    Use the foam type brush, the Elmers will wash out and the brush can be
    reused.
    Anything the 3M 77 gets on can't be easily cleaned.
    
    Terry

One of the things that has always slowed me up on bagging wings was preparing 
the sheeting. You have to trim the edges and then edge glue them into a solid 
piece. The glue joints become harder than the surrounding balsa and cause 
problems when flexing over the wing. You also have to prepare the sheeting in 
one session and then bag when it's dried. Not anymore!

Announcing the amazing Ronco sheet preparer. Send $19.95 to the above address 
and recieve our heartfelt thanks.

There, now that I've gotten that out of my system...

Over the weekend I tried sheeting a foam core with 1/32" wood without edge 
gluing the sheeting first. I trimmed the sheets as normal and used masking 
tape crossgrain to hold them together on the glue side. I then flipped them
over and taped the seams with 2" wide clear packing tape (that I seal my mail 
packages with. Very thin) on what becomes the outside surface. I then removed
the masking tape from the glue side and bagged the wing as I normally do. My
idea was that the epoxy on the sheeting would also glue the seams and the 
vacuum would hold everything in place. Last night I debagged the test wing 
and the results were exactly what I normally see. This mailing tape I used 
peels off well and the little bit of epoxy bleed at the seams filled them. 
Trim the ends and lightly sand and I had a nice wing. Now I can cut a core,
trim the sheeting and put it into the bag all in one session with limited
muss and fuss. Since it takes one session instead of two, I can double my 
output.

    Jim,
    
    how did you do it before? The way I learned to prepare sheeting for a
    fully sheeted wing is very similar: trim the balsa sheets, place them
    on a table and run a tape over the (very small) gap. Pick the assembly
    up, fold the sheets open at the gap and insert quickly curing glue
    (UHU-hart for example). Put it on the table again (tape on underside
    now) and run another tape over topside. After ten minutes (perparing
    the next sheeting), you can pull the tape off, slightly sand the 
    gluejoint and have a complete sheeting done.
    
    Of course, the guy I saw doing this did a very thorough job. He
    slightly sanded both sides of the joint. And got remarks like
    'Friedhelm sands his sheeting even on the inside!'
    
    Best regards,
                  Hartmut
    
    P.S.: Jim, you forgot the above address - or do you mean your mailstop?
          - and didn't say what Ronco stands for. I need some hints to name
          my product :-)

In the past I have used white (Titebond) glue which needs to dry for a while.
They discourage the use of CA glues due to the hard lumps that can develop.
This method allows you the same convenience since you can go directly to
bagging after preparing the sheeting. Sounds like the glue you use is similar 
to Ambroid in curing time. This method has the added advantage of uniform
flexibility of the sheeting while bagging. My glue joints tend to be stiffer
than the surrounding wood.

For those non-US readers, Ronco is a company name used in several comedy shows 
for a company which always has the latest multipurpose gadget. Commercials for
these products usually air at 3am on UHF (small local) TV stations.

They are famous for lines like "now how much would you pay? But wait, there's 
more! If you order in the next 10 minutes we'll include..."

    Thanks Jim!
    
    The most important bit of information I got out of that was the use of 
    packaging tape..  I bet the stuff works well for the trailing edge
    too..
    
    I had the same trouble using CA the length of the seam.  I then started
    to just use a few dots of CA to keep the pieces in place.  But then I
    got epoxy seepage that wasn't much better.  The tape should contain
    this well.
    
    Also, using this tape sounds better than masking tape for the trailing
    edge as it won't soak up (read bond) the epoxy.
    
    cheers,
    jeff
    

Yep, I first used this tape on the trailing edge and was so pleased with the 
results that I figured I'd give it a try on some disposable HLG cores. Besides, 
edge gluing 1/32" balsa sheet is a royal pain. I tried your scotch tape 
suggestion on the TE but found that the 5/8" tape didn't fold well and tended 
to lift and open the joint. I then tried masking tape OVER the scotch tape to 
hold it in place. I then noticed this big 2" wide roll in my shop and it 
worked very well all by itself. I've gotten into bagging mode and have been 
bagging a wing a night recently so there's been plenty of time to try new 
techniques. I generally try it out on a HLG core to conserve wood and effort 
(no spar structure) in case of a failure.

    
       I remember reading somewhere that Sig-ment was recommended for gluing
    sheets together due to the fact that it sanded much more easily than
    ca, epoxy, etc...
       I bought a tube to do the sheeting on my Ultimate Biplane, but I
    haven't ( will I ever?) got around to trying it yet.
    
                                                                  DW2

The August 1992 MAN has an article about building hollow core glider wings
using Rohacell (sp?) and fiberglass vacuum bagged over foam molds. It was 
a very technical article and I need another couple of reads to make sure I 
understand all the techniques. Looks interesting...

I did another few panels this weekend with the tape method and found that it 
worked even better with 1/16" sheeting. no muss, no fuss.

Last night Lamar gave me my half of a roll of bagging tubes we ordered from CST.
This stuff is nylon and 18" wide and comes on a continuous roll. The cost per 
yard was pretty cheap so we each got 10 yards. I checkewd it out last night and 
it seems really nice. I'll be bagging some stuff with it this weekend to check 
it out. Lamar gave me a couple of "zip locks" from a 3M window (draft sealing)
kit which look like they'll seal the ends super. The tubes make insertion a bit 
harder but give you less places to leak.

    That's good - you don't want your tube to leak. :-)  
    
    What were you saying about insertion?
    
    
    I need a weekend bad!
    
    
    
    

My tube DIDN't leak and the insertions were easier than I expected 8^)

I built a bag tap while I was gone. You take a 1/4-20 nylon bolt and you
put a nylon nut up at the head. Center drill the threaded part from the
end away from the head (but not out the head end) and then drill through 
the nut from the side on each face. Make sure you have clear air passage
through the bolt. Put a "fender" washer on this and a little PFM/silicone
caulk and insert it through the bag with the head/nut on the inside. Add
another fender washer with more PFM and another nylon nut and tighten it 
down. Be careful not to get any caulk on the air holes and you should have
a sealed bag tap for about a buck. I trimmed the end with an Xacto knife 
and pushed my aquarium tubing right over it. This, with the bags Lamar 
ordered and the zip lock window strips (I had to fold over the bag ends 3 
times for a good seal) worked great and is fully reuseable! You can make
the bag extra long and just seal it wherever the core ends.

I also bagged a HLG wing with posterboard (to test this setup on something 
low cost) and was pleased with the results.

    So Jim,
    
    You last talked about bagging with posterboard back a year ago...
    How is it working out??  Is there a weight savings??  Are you
    sealing it with anything to protect it from moisture??  What do you 
    do with the leading edge??  What kind of glue did you use??
    
    I am also thinking of using the glass method to preform fiberglass
    sheets, then bag these..  How are people doing with that method??
    
    Has anyone else done any more with using the brown postal paper??
    How has that worked out??
    
    I have also been considering one other alternative, although I would 
    need a new set of cores...  No sheeting at all...  I mean, in a
    HLG that you are not going to winch, what is the purpose of all of
    this??   I used clear packing tape as covering on a Gremlin and it
    worked well..  Why not just cover it with tape??  The tape will give it
    a smoother finish and some strength.  No, it is not going to last
    forever, but I bet the process would be fast enough that a couple of 
    extra sets of wings each year would not be a big thing..
    
    In this case, the cores would need to be cut without sheeting planned
    so that the airfoil is correct...
    
    Comments appreciated!!
    jeff
    

The posterboard works well. The cores become disposable. F77 contact 
adhesive is good enough. Leading edges and tips put on with Titebond 
and covered with vinyl tape (accent color of your choice). If you 
remember, we destructively tested that posterboard panel when I gave 
your club the cutting demo. That was an epoxy panel and the failure 
mode was delamination. I think using a notched scrapper would have 
solved that problem and they were plenty strong as they were. The
real point is that you want to find what's "good enough" to meet 
the criteria and I feel that quick is better than pressing with 
epoxy for these tests. A core and $.20 worth of poster board and 
you can do a set of panels in half an hour. It takes me that long to 
get the press going. I still use the press to put on the posterboard 
but I don't sock down the threaded rods for overnight. I just use 
them as guides for the top piece and add some weight to get good 
contact and then unstack and check. 10 minutes is too much 8^) My 
goal for saturday is to do a dozen wings in a few hours. That's the 
time I have allowed and the goal I've set. I'll use fiber tape on 
the outside bottom surface to reinforce and packing tape for hinges.

Sal has mentioned that you can buy fiberglass sheeting premade and
I'm trying to find out where.

I did a set of glider wings with packing tape. Glider wings don't 
have enough structural strength (read thickness) to keep from 
warping. Gray foam might help. The UAS-1 used blue foam with no 
covering and half span spars. This worked well but the leading edge 
needed more support.

A bad handlaunch can put plenty of stress on the wings so you need 
some fiber tape on the bottom of the wing anyway.

I'm doing a batch of posterboard wings this weekend for a slope 
trip out to Otis to check out a site on the 13th. I'll let you 
know how they work out after a day of flying. I'm planning on doing 
some no spar aileron wings for the heck of it. I'm going to try to 
bring about a dozen sets of wings and see how different combinations 
work out.

It's a pretty cheap way to experiment and you can cut a dozen sets 
of wings with one setup and do different things to each to see what 
works best. Use marker on the posterboard so you can tell the 
winning combination without having to dissect it to see which wing 
it was. It's also a great way to do airfoil testing if you have the 
time to do the different setups on the cutter. Having a set of cores 
with the wrong sheeting allowance won't bother the testing of the 
method and I'm not convinced I can tell the difference in my 
attempts. Maybe a Joe Wurts can tell the difference a few thousandths 
makes but not me cranking planes around differently every flight. 
We just aren't as consistant as the big boys yet.

>>> A bad handlaunch can put plenty of stress on the wings so you need 
>>> some fiber tape on the bottom of the wing anyway.
    
    Ditto that. If you throw the thing hard at a high angle of attach, you
    can easily fold the wings. I did it once to my 2M Riser... admittedly
    the wings were poorly joined in the first place.