Conference vmszoo::rc

    
    	Tom,
    
    		I have never worked with a sheeted foam core wing 
    	before so I do not know what you mean by a core saddle.
    	Could you explain?
    		I found the information informative and clear up 
    	to the point of where the saddle came in.
    
    				Michael Gallant
    

    
    	Sure Mike,
    
    	To understand what a foam core saddle is you would have had
    to seen a foam core or made some core yourself. In the process 
    of making a foam core for a wing you cut the core out of a solid
    block. The resulting excess block that is an inverse mirror 
    image of the of the wing core is what I call the foam core saddle.
    Realize that a foam core wing is cut using a heated wire guided
    by a template. I hope this clears up your questions.
    
    
    						Tom
    wing core

From one who has tried the lot Epoxy is definitely the way to go. As I see it
the advantages of Epoxy over the spray adhesives and other contact type of
adhesive is that; 
1) You have a second chance to reposition the sheets once they have made 
   contact; 
2) You have less chance of building in warps in the wing; 
3) And you end up with a stronger more ridged finished product. 

I have a few suggestions to expand on Tom's note that I believe make life 
easier.

In the old RC Note file (RIP!) I gave details of the Epoxy I use. It is 
manufactured in America by Adhesive Technology and is called West Epoxy. It is 
a marine laminating and finishing resin, it is much thinner than the tube Epoxy 
with a consistency at room temp similar to 20 grade engine oil. The trouble 
with thinning the epoxy with heat is that when it is applied to the skins it 
very quickly cools and becomes thick again.

Another suggestion is to use clear adhesive tape rather than masking tape and 
to join the sheets with any CA (Zap etc.). The benefit of the clear tape is it 
pulls of cleanly where the masking tape leaves bits behind. I use the CA 
because it is quick and I am inpatient, the epoxy actually does the final 
join of the sheets the CA just tacks them together.

After the sheets are joined and the tape removed place them on a smooth surface
and go over them both sides with an orbital sander, this will remove any ridges
and ensure a flat surface for the epoxy. Don't worry about thinning the sheets
as the strength loss is minimal and careful use of fiber glass on the wing adds
all the strength you need. I personally never use thicker than 1/16 sheet on
any model. 

Next as Tom says set up the cores and dust the everything with the vacuum
cleaner and go for it. Don't put the epoxy onto the cores as the cells in the 
cores absorb the epoxy and add weight. 

Any Questions?.

John

When you join wing cores first cut some scrap balsa the length of the wing tip
cord and the height of the dihedral lift of each wing + the distance from the
bottom of the wing to the center line of the core. CA the balsa pieces to the
wing tip with one edge along the center line so as when the core is placed on a
flat surface the wing tip is now elevated to the correct dihedral. 

Once the operation is completed to both wing panels place both panels
together on a flat surface and sand to match and epoxy together. Don't worry
about one wing root being slightly higher than the other as it is more
important to keep the tips level. If you let the tips vary you will have a
warped wing and a difficult to fly model.

Epoxy a glass bandage of 6oz cloth around the center, it  should be 1 1/2"
wider than the width of the fuselage. Depending on the size of the model and
the desired strength further glass should be put on the wing to approx 1/2 the
total span. I have found  2 1/2oz satisfactory in all applications up to an 84"
CAP, larger models would probably require a little more I would guess may be
4oz.

To finish the wing is sanded with an orbital sander, prime and paint. I hope 
that makes sense, it is difficult to describe without pictures.

John

    
    	John, Why don't you write a detailed account of how,where and
    why you cover with fiberglass cloth. I shall do the same. Add the
    article to this note and we will have an all inclusive note. What
    do you think?
    
    						Tom

re:-.1 Ok Tom this is my story on the use of fiber glass on wings. 

Let us first accept that the foam core provides little if any strength, its
sole purpose in life is to keep the core skins apart to allow the strength to
be attained by the "lamination". When I refer to glass I am referring to glass
cloth and NOT chop strand mat. Their are many types of glass cloth that can be
used but for most applications the ordinary weave is satisfactory and least
expensive. The "S" cloth and "E" cloth are the most common of the exotic
weaves, the main use is for laying up molds with complex profiles. If you have
problems getting the cloth into tight corners they are a good alternative but
more expensive. Glass rovings (glass strands formed into a strip) can also be
used to good effect when used like a spar or included into filets.

There is no reason why we must use balsa to sheet the wings, it is popular
because of its ease of use, convenience and low cost. I have used fiber glass
sheet to cover wings which proved successful, I have also seen paper used as
the sheeting material, that proved not to be so successful. Sheeting is 
necessary to provide strength and resistance to wear.

Restricting ourselves to the balsa and fiber glass method of wing sheeting let
us continue. If we take an "average wing" it has certain areas where the stress
is high. These areas include adjacent areas to the fuselage, wheel wells (when
retracts are used), wheel assembly mounting areas, and the corners of aileron
cutouts. Also to be considered is the purpose of the model. An Aerobatic model
is certain to perform high "G" maneuvers in both the positive and negative
direction, where as a pylon model will experience only very high positive "G"
loading. The Aerobatic model will require strength added to the upper and lower
surfaces of the wing, the pylon racer only requires extra strength on the lower
surface. What I am saying is you apply the glass to the area's of the wing that
require it and not to the area's that don't need the extra strength, each model
is different and with some experience it is not difficult to determine those
high stress area's and act accordingly. 

Fiber glass will add strength in two ways firstly by resisting the tendency for
the wing to compress (ie: on the upper surface during a +ve "G" maneuver) and
secondly and mainly in the tensile mode (ie: on the lower surface during a +ve
"G" maneuver). 

An important thing to remember when laminating glass on wings is to never have
a join on a weak point or directly opposite a similar join on the other side of
the wing. I also make a policy of never cutting the cloth straight across the
wing I always use a diagonal cut (say 60�) and the cut is from the leading edge
towards the fuse at the trailing edge so as any bending of the wing during a
high "G" maneuver gives "wash out" rather than "wash in". A model with "wash
in" on the wing is difficult to fly and unpredictable in turns. 

I applied glass in the following way to a 72" CAP21; 6oz around the center
section just wider than the fuselage; 2 1/2oz top and bottom to approximately
half the aileron length; 3/4oz across the bottom only (optional). On my FAI
Pylon models I also glass the top of the stabilizer to give some rigidity
during the turns. Always blend out a join; that is remove a few strands from
the weave so as the fibers along the wing are able to lay flat, this stops
having a weak point caused by an abrupt finish of the glass. 

I resin the whole wing even those parts that not covered by glass and finely
with my trusty orbital sander smooth out the lot. It is very easy to leave too
much material on the wing and difficult to to see it once it is their, the
preferred method is to apply the minimum resin to do the job required so the
final sanding leaves you with a smooth even finish that the paint will adhere
to. I apply resin by pouring it on the wing and spreading it with a scrap of
1/16" balsa, I leave the finish with the cloth texture just showing through.
The final sanding does not remove this texture I fill that with a heavy coat of
primer which is sanded off completely except for that which remains in the
holes. 

You can cover the fuselage and tail in the same manor using glass and resin,
with some practice it is a lighter construction method than the more
conventional techniques, I made a Great Planes CAP21 from plans with an OS90FS,
the all up weight ready to fly was 6lb 15oz. 

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

Do you find yourself itching after sanding fiber glass?. try rubbing Talc
powder over your hands, arms, and legs (if you wear shorts). It stops the glass
fibers sticking to you and causing the itch. 

    JOHN;TOM:
    
    LAST SUNDAY I LOST MY FIRST F1 PLANE WHILE RACING IN CALIF.
    THE WING FOLDED WHILE TURNING THE NUMBER 1 PYLON. BOTH HALVES
    STAYED INTACT UNTIL IMPACT. IT APPEARED THAT THE TOP OF THE
    RIGHT WING CRUSHED RIGHT AT THE FUSELAGE. I HAD BOTH CARBON FIBER
    AND PACKING TAPE BETWEEN THE WOOD AND FOAM CORE ON THE BOTTOM
    . WOOD WAS 1/16 WITH GLASS SIMILAR TO YOUR ARTICLE. WING WAS 1 IN
    THIN AT CENTER. IN READING YOUR ARTICLE I SEE WHAT MIGHT HAVE BEEN
    MY ERROR. I HAD A STRIP OF 6 OZ. ONLY 2 IN WIDE IT THE CENTER
    TOP, THEN THE WHOLE TOP COVERED WITH .5 OZ GLASS. I MIGHT NEED MORE
    GLASS (WIDER) ON THE TOP CENTER?????????? ANY IDEAS I'LL TRY.....
    
    THANKS, 
    
    BOB
    
    

    
    	I think that if you were to look at a wing like it was made
    it 1/3 you would fine that the majority of the stresses our
    wings see are in the middle 1/3. On most pattern designs it's
    the middle 18-21 inches of wing that carry app 80% of the flight
    loads. If possible you should try and detail how the wing failed.
    If you have built a second ship similar to the one that failed and
    if it has about the same flight time on it, it might be a good
    idea to check that second wing for stress cracks and any possible
    signs of a failure. Definately you need to extend the glass out
    over the wing. I have a Q500 on the board now and have 6 oz. cloth
    extending out app. 5" on either side of the fuse.
    	Can you detail the Q500 rules that govern the texas area for
    me?  A few of us here in Mass. will be trying out Q500 for the
    first time this year. I know that some rules will be different but
    I'm still interested in your rules.
    
    						Tom

Re: 91.7

Hi Bob, 

You have the problem in one. As Tom said in -.1 the heaviest loading in in he 
middle 1/3 of the wing. By extending your 6oz glass on the center section of 
the wing past the fuselage, you will spread the load  over a greater area.

The loads on a pylon model rounding No. 1 are immense, the engine out front is 
trying to keep going in the same direction while the wing is forcing it to 
change direction; the majority of that load is applied to the leading edge 
of the wing where the fuse sits.

Bob have you thought of using a thicker wing to get better lift around the 
turns. Look at some of the critical wing sections like the NACA 66210. We find 
they round the turns much better than the thin sections like the Tony uses.

John.

    I finally finished sheeting my latest glider wing, 1/32" obechi
    over white foam cores. Some thoughts on using obechi:
    
    Compared to 1/16" balsa sheet it's more brittle, has more of a grain
    but sands pretty easily with less dust.
    
    Sticks to white foam very well with laminating epoxy(I used Saf-T-Poxy)
    and simply weighted the core beds with 80 lbs. of barbell weights.
    
    DO NOT use water base contact cement. I've had good results when
    used with balsa but obechi doesn't seem to like it. Poor adhesion,
    ripples and bubbles. Had to redo one wing panel, and switch to epoxy.
    
    Sanded with #400 then #600. Finished with two coats, brushed, of
    clear polyurethane furniture finish, sanded lighty with #600
    between coats. Makes a nice slick, glossy , durable, ding resistant
    finish. A color coat would require more sanding and filling to hide
    the grain.
    
    Conclusions: I'll use up the supply of obechi on hand, but skinning
    technology has moved on, and veneers of birch, pine, mahogany,
    will be the way I go in the future.
    
    Terry
    

    Terry,
    		Where are you purchasing these veniors? What thiskness
    do they come in, what the weight like compared to balsa, what's
    the strength like and what's the cost like?
    
    
    Tom

    reply
    re.36
    
    Tom, I assume you're referring to the birch,pine,and mahogany veneers
    not the obechi.
    
    They're available at a local lumber yard. 4X8ft. sheets for $32.
    Smaller sheets available at a higher cost per ft. You would
    need a micrometer to accurately measure the thickness, I'd estimate
    it at around 1/48". I haven't used it myself yet, but have examined
    the mahogony stuff pretty closely. It's a lot harder than balsa
    about as flexible when cut to typical wing sheet size. Not as prone
    to splitting as obechi. No doubt it's heavier than light balsa,
    but I can't notice any significant difference compared to run of
    the mill hobby shop balsa. I'm sure it's lighter than 1/64" ply.
    
    A couple of the guys locally are getting ready to cover some cores
    with it. I'll have more details to report later.
    
    One thing for sure, you avoid having to do much,if any, sanding.
    
    Terry
    

Everytime I hear you guys talk about putting urethane on the veneer, I think
of that thick, heavy stuff I've used to cover wood furniture. Is that what
you use? Or do you thin it down? Does it add an appreciable weight to the
wings?

Dave

    re.15
    
    I guess it's heavy. I don't thin it. On a 946 sq. in. wing it added
    2.9 oz. with one fairly heavy coat and one light coat. With a total
    aircraft weight of 65-70 oz. I can live with that percentage. I
    like the hard ding proof finish, more useful to me than absoulute
    max. lightness.
    
    Terry
    

                          -< Veneer source located. >-
--------------------------------------------------------------------------------

    	
    
	I have located a possible source of veneer for those that want to
    skin their foam wings in something other than ply or balsa. It's a
    place called The Woodworkers Store in Boston. They sell a line called 
    
    "Flexible veneers":
    	Real wood veneers 1/64" thick laminated to a special backing and
    made pliable by a process that assures dimensional stability. Cuts
    easily with a scissors or razor and is applied aith contact adhesives.
    Finishes like any other real wood. May be sealed, stained, filled and
    finished with top coats. Flexible so it can be applied to curved
    surfaces. Apply to metal, plywood, partical board, etc. Grain runs the
    length. Sold by the full sheet only.
    
    	If you're intersested in the price list, send me mail and I'll send
    you a xerox of the catlog page. The average price for a 3'x 8' piece is
    around $60.
         __       *   *        *
    * __|__|__  *    *    *     *
  *     (**)   V *  _______|_______ *
   *   (    )--| *         0  *  	   	
 _____(______)_|_________U___U______*___
	                
      "The Sno-man"			

    Well, I looked around and couldn't find it documented (although I am
    sure that a lot of you are already aware...)
    
    		DO NOT USE POLYESTER RESIN DIRECTLY ON FOAM
    
    I probably should have thought more about it or asked, but I just
    blindly went ahead with covering a cheek block for one of my Eindeckers
    that I had just cut out of foam, with glass and poly.  At first, I
    didn't realize what was happening.  Then it made sense....  the foam
    was disolving from the polyester resin.
    
    Scratch one cheek block.  Luckily, we had cut spares....
    
    cheers,
    jeff
    

    I moved the cutter side discussion to topic 56, "cutting foam, 
    especially foam wings".  Since I have the listing on my screen, 
    I'll leave the directory of topic 56 here FYI.
    
    This entry will be deleted in a few days.
    
    Directory of topic 56:
    
        SPKALI::THOMAS        8-APR-1987   56.1  RCM book on Foam Wings
        CRVAX1::KAPLOW        8-APR-1987   56.2  Homebuilt Aircraft books
        CRVAX1::KAPLOW        8-APR-1987   56.3  Hot Wire note from 'old' RC.NOTE
         TYCHO::REITH         3-FEB-1989   56.4  Want instructions?
         TYCHO::REITH         3-FEB-1989   56.5  1st pass at core cutting instructions - Comments/questions?
        TEKTRM::REITH        10-JAN-1990   56.6  device and technique; moved by moderator
        WR2FOR::BEATTY_WI     5-FEB-1989   56.7  Wing Mfg makes custom cores
        ABACUS::RYDER        26-DEC-1989   56.8  home-made foam wings to replace balsa built-ups
         CSC32::M_ANTRY       3-JAN-1990   56.11  Foam it and fly!!!!
          LEDS::COHEN         3-JAN-1990   56.12  Never broke the wing, though.
        ABACUS::RYDER         3-JAN-1990   56.13  the first will be wood and foam
         CSC32::M_ANTRY       4-JAN-1990   56.14  Whatever you can shoehorn in....
        CTD024::TAVARES      11-JAN-1990   56.15  Nichrome wire is easy to get
        WILKIE::EDDINGS      15-JAN-1990   56.16  nicrome wire??
        HANNAH::REITH        15-JAN-1990   56.17  SIG item # SH-135 = 5 ft of Nichrome wire
        NYJOPS::BOBA         15-JAN-1990   56.18  Alternatives
        GIDDAY::CHADD        15-JAN-1990   56.19  Try an electrical store
          9667::ARYDER       15-JAN-1990   56.20  but at less than 5 Ohms per foot
        GIDDAY::CHADD        16-JAN-1990   56.21  use a light dimmer for control
        CTD024::TAVARES      16-JAN-1990   56.23  There you go with that blue foam stuff again...
        GIDDAY::CHADD        16-JAN-1990   56.24  temperature is unknown
        ABACUS::RYDER        16-JAN-1990   56.25  boring detail about hot wires
        CTD024::TAVARES      17-JAN-1990   56.27  use a hacked up battery charger
        NYJOPS::BOBA         17-JAN-1990   56.28  More on cutting wire selection
          ISTG::HUGHES       17-JAN-1990   56.29  please be safe!
        CTD024::TAVARES      17-JAN-1990   56.30  hmmmn   resistance would vary
             K::FISHER       17-JAN-1990   56.31  Current limiting?
        CTD024::TAVARES      12-FEB-1990   56.33  Foam cutting demo on DECRCM tape
         MAMIE::EDDINGS      12-FEB-1990   56.34  Wish to see tape
         CSC32::M_ANTRY      18-JAN-1990   56.35  OK OK Heres the way to do it.
        ABACUS::RYDER        12-FEB-1990   56.36  re   56.34 --- see note 1115.11
         AES12::BOBA         13-FEB-1990   56.37  There always other ways to do it.
        WRASSE::FRIEDRICHS   28-MAR-1990   56.38  making the channel in the wing
         39463::REITH        28-MAR-1990   56.39  Things I've tried that worked...(your mileage may vary)
         CURIE::ANKER        28-MAR-1990   56.40  Use spackle
         39463::REITH        28-MAR-1990   56.41  Not a rebuttle, just further argument ;^)
        GALVIA::ECULLEN      28-MAR-1990   56.42  More on Control cables in foam cores.
         CSC32::M_ANTRY      28-MAR-1990   56.43  Putem in the Wang
         39463::REITH        28-MAR-1990   56.44  NOT foam wings but a related question.
        ELMAGO::TTOMBAUGH    28-MAR-1990   56.45  no weight problems with servos
        GALVIA::ECULLEN      29-MAR-1990   56.46  Active leads...
         39463::REITH        29-MAR-1990   56.47  I'm interested
         CSC32::M_ANTRY      29-MAR-1990   56.48  Slope a rope
        WRASSE::FRIEDRICHS   10-SEP-1990   56.49  templates
        NEURON::ANTRY        10-SEP-1990   56.50  FOAM CUTTING TEMPLATES
           KAY::FISHER       10-SEP-1990   56.51  Laser?
        NEURON::ANTRY        11-SEP-1990   56.52  SMOKIN.....
        GIDDAY::CHADD        11-SEP-1990   56.53  Aluminium for templates
        ULYSSE::FROST        14-SEP-1990   56.54  Tks for the cutter
        WRASSE::FRIEDRICHS   14-SEP-1990   56.55  
        NEURON::ANTRY        14-SEP-1990   56.56  Here's a couple of tips and then ask away
    

    I hate this remote editting with periodic crashes. - Take 2
    
    Sounds like its worth the effort to cut a wedge out and open up the bottom 
    and then replace the wedge afterwards (for curved cuts). The wedge would
    support the pressure from the skins better and have the same
    characteristics of the surrounding area. Keep the tips coming since it
    could save a couple of foam blocks in the experimentation stages.
    
    Questions for John Chadd:
    
    When you lay out your glass on the glass (confused yet) and use it as
    sheeting", does it remain flexible enough that you can wrap from the
    top trailing edge around the leading edge and back to the bottom trailing 
    edge to avoid the leading edge seam? Do you lay up graduated layers of
    cloth to increase the strength as you move inboard? Do you insert the
    carbon fiber reinforcement into the laminate or place it on the core 
    before you epoxy and wrap it? What weight cloth seems to work out the 
    best?
    
    Thanks for the "drilling" tip Jeff. I'm looking at non-straight runs
    also though (but I'll probably try to avoid them as much as possible)
    
    Here's a related question:
    
    If I use torque rods, is it better to use a longer rod, well supported
    and hook in at the middle of the surface to center the movement or to
    put it into the end like a strip aileron typically is and have the 
    torsional effects as you move towards the tip?

Re: Note 91.37 by ZENDIA::REITH 

Jim,

>    Questions for John Chadd:
    
>    When you lay out your glass on the glass (confused yet) and use it as
>    sheeting", does it remain flexible enough that you can wrap from the
>    top trailing edge around the leading edge and back to the bottom trailing 
>    edge to avoid the leading edge seam?

I have never done it but I would suggest it depends on the radius of the
leading edge, also a straight leading edge without dihedral. Given a modest
radius it would probably be ok but care would be necessary to ensure a proper
fit around the leading edge. You could laminate the leading edge section out of
light cloth. The glass is flexible but a little dependent on temperature and
age of the layup and the resin. With no more than 2-3 days of curing it is
still flexible and should follow most curves. Remember to use epoxy not
polyester resin. 

>                                         Do you lay up graduated layers of
>    cloth to increase the strength as you move inboard? 

Yes, I forgot to mention that. You lay up the layers just as you would glassing 
a Balsa sheeted wing.

>                                                        Do you insert the
>    carbon fiber reinforcement into the laminate or place it on the core 
>    before you epoxy and wrap it? What weight cloth seems to work out the 
>    best?

I have never needed any sort of spar so have not tried. Interesting thought to 
experiment with. I personally don't like lengths of carbon in wings or 
fuse because of potential radio problems. I know people who do use it and 
have never had a problem that can be attributed to the Carbon reinforcement. 
Under tensile load Kevlar is close to carbon in performance, but it a bitch to 
cut and impossible to sand.

John

    Thanks John.
    
    I watched the foam cutting video last night and there is an automatic (or 
    is that autoMAGIC) cutter in my very near future.
    
    One more thought...
    
    What about combining the methods and laying up the glass on a piece of
    mylar and while still wet, wrapping it around the core? This would give
    the smooth outer surface as well as the savings of only having the weight 
    of the "sheeting" without the second application of epoxy for the "glue"? 
    Just trying to get this straight since I'll be doing it soon as I get the 
    cutter done.

>    What about combining the methods and laying up the glass on a piece of
>    mylar and while still wet, wrapping it around the core? This would give

The mylar that they sell for wing glassing it too thick to make the sharp
bend for the leading edge.

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

    Last evening Jeff and I cut the dihedral face of one of our balsa
    sheeted, soft foam wings.  We used a radial arm saw, tilting the blade
    for the angle.  The 7.5 tpi veneer blade was mounted backwards and run
    at the slow end of the speed range.

    This set up worked very, very well.  There was no splintering of the
    balsa, no melting of the foam; the cut is clean, although the leading
    edge was a bit burned from the friction of the backwards blade.

    OK, I am actually finally building the Eindeckers that we cut the
    wings for in Feb...
    
    So, what I have is white foam sheeted with 1/16" balsa.
    
    My question is, what kind of covering(s) can I use??
    
    So, what I would like is for anyone with experience in covering foam
    wings with iron on coverings to fill in whatever blanks you can and
    mail them to me.  I will compile the information and repost it...
    (footnotes on temp range, etc are welcome)
    
    
    
    Key:  AD - Advertised to work
    	  US - Used Successfully, no problems
    	  UP - Used with problems
    	  NC - Not compatible

                 Unsheeted Foam			Sheeted w/
    Covering  |	white 	 |  blue      |	veneers	|  <1/16 balsa|	>1/16"balsa|
    ----------|----------|------------|---------|-------------|-------------|
    	      |          |	      |         |             |             |
    Monokote  |          |	      |         |             |             |
    	      |          |	      |         |             |             |
    ----------|----------|------------|---------|-------------|-------------|
    	      |  AD      |	AD    |   AD    |    AD       |    AD       |
    Econokote |          |	      |         |             |             |
    	      |          |	      |         |             |             |
    ----------|----------|------------|---------|-------------|-------------|
    	      |   AD     |	AD    |   AD    |    AD       |    AD       |
    Black Bar |          |	      |         |             |             |
    	      |          |	      |         |             |             |
    ----------|----------|------------|---------|-------------|-------------|
    	      |          |	      |         |             |             |
    Super Cov |          |	      |         |             |             |
    	      |          |	      |         |             |             |
    ----------|----------|------------|---------|-------------|-------------|
    	      |          |	      |         |             |             |
    Permagloss|          |	      |         |             |             |
    	      |          |	      |         |             |             |
    ----------|----------|------------|---------|-------------|-------------|
    	      |          |	      |   AD    |   AD        |    AD       |
    Micafilm  |          |	      |         |             |             |
    	      |          |	      |         |             |             |
    ----------|----------|------------|---------|-------------|-------------|
    	      |          |	      |         |             |             |
    Ultracote |          |	      |         |             |             |
    	      |          |	      |         |             |             |
    ----------|----------|------------|---------|-------------|-------------|
    	      |  AD      |	AD    |  AD     |   AD        |  AD         |
    Colortex  |          |	      |         |             |             |
    	      |          |	      |         |             |             |
    ----------|----------|------------|---------|-------------|-------------|
    	      |          |	      |         |             |             |
    	      |          |	      |         |             |             |
    ----------|----------|------------|---------|-------------|-------------|
    	      |          |	      |         |             |             |
    	      |          |	      |         |             |             |
    ----------|----------|------------|---------|-------------|-------------|
    
    
    
    Cheers,
    jeff
    

    I successfully used opaque yellow Monocoat over 1/32" balsa sheeting
    applied with Hobbypoxy II over white foam.

    Another two columns --- fiberglass with epoxy and with polyester resin.

    Don't use Polyester resin over foam (even with sheeting in place)
    You'll discover that you won't have foam under your glass when the wing
    breaks.

    Ok. The Alcyone has some wonderful cores included and they are built
    fully sheeted with 1/16" balsa. I don't want to monocoat the wings so I
    was considering vacuum bagging a layer of .6oz cloth and epoxy over the
    top with mylar as a finish surface. What other options do I have for
    finishing sheeted foam wings? I would think that normal sealing and
    painting would be too heavy and too time consuming. What have others
    done?

    I think you've listed all the options Jim.
    
    I'd go with the cloth/epoxy/mylar. Gives the most durable finish and
    you could do the color transfer trick too. 
    
    I might go with ~1oz. cloth though. .6 oz. is a little thin for one
    layer, might show the weave too much, although with the paint transfer
    you might get by. 
    
    Try it on a stab half first.
    
    Terry

    No, I don't have the cores sheeted (YET!) but I got Lamar's attention
    8^)
    
    I guess I don't understand why thinner cloth would show more weave? My
    available cloth is .6oz, 1.5oz, 3oz, and 6oz. I'm planning to use a
    triangle of 1.5 over the spar to distribute the stress a little more
    (between foam and sheeting top and bottom) and in the aileron servo 
    area for the same reasons.

    One more thing. The stabs are stick built from 1/4" stock so they
    wouldn't need bagging. I will be making some replacement foam stabs 
    to practice and will probably try making some with and without 
    sheeting (glass only)
    
    Looks like a good 4 day weekend to build. It's supposed to be a high in
    the 20's all weekend and brisk winds. Fire up the shop heater right
    next to the vacuum pump 8^)

RE .63 Jim,

>>    No, I don't have the cores sheeted (YET!) but I got Lamar's attention
>>    8^)

Boy! You better believe you did. I better get a move on with the Pulsar!!!

-Lamar

    This is your last warning (I already have all the PAINTING info I need
    8^)
    
    I think you stopped over just to give me the flu to slow me down for
    the weekend 8^) 8^)

Well since I couldn't find any of Jim Cavanagh's "balsa-slo", I had to resort
to something else! :^)

-Lamar

    One idea you may want to consider is to use silkspan as the covering nd
    dope with very thin dope.  This process is used in the all sheeted
    warbird I am building from scratch.
    
    Just my 2 cents worth.
    
    Regards,

    While sheeting the Alcyone wings, I found that the masking tape that
    held the trailing edge sheeting together got stuck to the epoxy. After
    picking/sanding it off (and the memories thereof) I started looking for
    alternates. Has anyone found anything better for this? I was thinking
    that plastic tape might hold together better during removal.

    I haven't tried plastic tape.
    When using masking tape you can use several short pieces rather than
    a full span piece, or you can cut a narrow piece of wax paper, ~1/2 the
    width of the masking tape and fold it over the t.e. then tape over
    the top with the masking tape. The area where the epoxy oozes (?)
    out will be covered by the wax paper.
    
    Terry

    Jim,
    	Could you use zap to tack the TE together?  UFO would not eat the
    foam.  Plastic packing tape might work, but it tears very easily and
    I've had trouble removing the adhesive.
    
    Charlie
    

    The epoxy and fiberglass tape work well for a knife sharp and straight
    trailing edge. The tape is mostly to keep the skins aligned and act as
    a hinge before they actually go into the bag and get clamped. My kids
    have some cheap colored plastic tape (electrical tape in colors) which
    wasn't too expensive and seems tough enough to peel off. I can handle
    the adhesive removal if I can get the adhesive "carrier" back off
    without having to sand it off.

    Actually Jim, we had pretty good success using regular "Scotch" tape.
    It was much easier to remove than masking tape.  Yea, it rips into
    smaller pieces at times, but if you pull it right, it holds up pretty
    well...
    
    cheers,
    jeff
    

    Well, how often do you do a destructive test on a wing???
    
    Last night after flying, Dan Eaton, Joe Marrone and I retired to my
    place for a home cooked meal and to show off my auto foam cutter and
    bagging setup.
    
    When I first started playing with this stuff, I made up a few panels
    and I had butt glued 2 panels (with dihedral) together.  I then cut a
    slot in the joint, layed in some carbon fiber, and poured in some CA.
    The carbon fiber was supposed to work as a dihedral brace.
    
    Well, after the CA set up, I gave the two panels a good tug, nothing!
    Dan and Joe each took a try at breaking it and were surprised at how
    strong it was.  So, the second time around, I really tried to bend the
    joint...  SNAP..  Sure enough, it eventually broke.
    
    Actually, only about half the joint broke..  From the rear carbon fiber
    spar forward.  The butt joint to the trailing edge was still intact. 
    We then attempted to break this joint as well.  This too took some
    effort.
    
    Looking at the pieces, we all came to the conclusion that the cut (or
    kerf) in the wing/joint appeared to contribute to the break, rather
    than strengthening it.  I think in the future I will simply run a few 
    strands of CF flat over the joint.
    
    Granted, this is only a sample size of 1, but thought others would be
    interested..  Also, I was not able to fill the entire cut with carbon
    fiber.  The carbon fiber/CA was also still tacky in a couple of
    spots...
    
    cheers,
    jeff
    
    
    

    I have a dumb question related to trying to not have to learn how to
    vacuum bag.  In Satellite City's ads for their UFO CA they talk about
    applying fiberglass or kevlar directly over foam with their product.
    
    What would be the drawbacks to using this method to stick down the
    kevlar and then use epoxy to cover the kevlar with say 1 oz glass to
    provide a smooth sandable surface?
    
    What advantages does vacuum bagging provide over the above method?
    
    Thanks for any info.
    
                                                             Jim

It would probably work fine but the cost of doing an entire set of wings will be
pretty high. I've done a built up wing center section with CA and glass and the 
problem I see if the fact that the glass can get lumpy and sanding CA is a b*tch
(but then Kevlar would make it worse). The foam is going to act as a sponge and 
the CA will get expensive fast. The built up wing was most successful in the 
sections I flooded with CA and stretched the cloth over. The foam will soak in 
the "flood" before it has a chance to capture the cloth. The soaking of the foam
with CA will cause it to loose it's flex and become rigid and brittle. Vacuum 
bagging allows you to get everything laid out smooth and then provide uniform
pressure to ensure good contact everywhere. With the CA method, once it kicks,
it better be right. Read the topics on covering foam wings (do a dir/title=foam 
11.*) and give it a try. My biggest obstical in doing it was getting the courage 
up to do it the first time. If you've got concerns about it, buy a complete
package from Weston or NSP. If you're going to spend the money on Kevlar, the 
vacuum bagging equipment is noise level stuff. Besides, how are you going to 
apply the epoxy and glass outer surface? painting it on and filling in the 
valleys is going to be pretty heavy.

    re .1399
    
    You're asking for trouble in attempting to cover a large area with
    UFO/kevlar.
    
    As Jim R. says, it's ok for center sections or small areas where the
    total necessary amount of UFO can be applied within a few seconds.
    
    What happens on large areas is that the cure time varies and it is
    impossible to apply the UFO in wide brush strokes as with epoxy.
    The result is bands or patches of UFO that is non-uniform in thickness.
    
    This causes problems from then on, and even after covering with
    glass/epoxy the bumps, ridges, depressions are still there.
    
    Of course you could have a bucket of UFO on the bench and slap it on
    with a wide brush. 8^)  8^). The mind boggles.
    
    Try the vacuum bagging. After the initial investment, and a little
    practice, you'll like it. It will expand your construction skills
    repretoire and allow you to explore the sunny uplands of high tech
    building, where puffy cumuli float, thermals abound, and soaring
    groupies in green bikinis waltz. Sorry, the mind goes when you've
    got 2 days left.
    
    Terry

    re .1401
    
    You'll really like that maple veneer. I did a set of ~118" wings
    with it, a couple of years ago and finished them with clear urethane.
    
    Got a lot of compliments on the appearance, but the performance didn't
    measure up. Wasn't the fault of the veneer, although inch for inch
    they were the heaviest wings I ever built. Still have them BTW.
    
    Terry

I've been asked to sheet some wings and decided to use a press to try to 
get my throughput up. The following is a description of the press I'm 
building.

I went out and got two sheets of something called "signboard" which is 
used to (duh) make signs. It has one perfect surface which has some sort
of paper coating over somewhat normal plywood. I got 3/4". I also got some
1"x2" wood and cut the signboard into 16"x48" pieces. I then made a frame 
of 1x2s around the edge of the "bad" side and put a couple of crosspieces 
inside. All this was screwed and glued from the inside. I then coated the 
1x2s with glue and screwed another piece of signboard to the outside. 
These are my intermediate layers. The top and bottom layer will have 
waferboard "outsides" that will come in contact with the outside world 
(only be one good face). These will all stack up on 1/4-20 threaded rods,
4 along each long side, which will keep things together. Each layer will 
be secured from both sides with a nut and washer so the stack can be 
disassembled from either end (add to it from one end and then empty the 
oldest layers from the other end) Beds for the press will be extruded 
foam to provide a firmer surface for pressure. The wings will initially 
be obechi sheeted with glass and kevlar cast on plate glass as a future 
option. The initial orders will be done in 2-3 weeks so I'll update my 
success with this method in the near future. I decided to go with the 
press method so I could maintain more "work in process" than my vacuum 
pump would reliably do. I hope to do a full set of panels in a session 
which would normally require 3-4 separate bags and the associated hoses, 
connections, leak chasing. The press will allow new wings to be added 
incrementally without having to reuse the previous set of "tools". Each 
layer weighs about 25 pounds and the assembly is very sturdy and will be 
able to be moved around the shop without worry once assembled.

    re: -1
    
    Sounds like you did a nice job on the press, Jim.  Mine is constructed
    out of 3/4" plywood(48" long) with 4 maple cross pieces(12").  Omiting
    pieces running lengthwise was a mistake.  When I torque down the bolts
    the plywood flexes in the center.  I definitely need to add some 
    longitudinal support.
    
    As we speak my first wing is sitting in the press.  It is a pink foam
    core with carbon tow spars top and boot, 1/2" .007 carbon tape at the
    training edge, .7 oz glass over the whole core with a piece of 1.8 oz.
    kevlar over the wing holdown area and the servo cutout area.  The
    whole wing is sheeted with 1/32" balsa.  This was all done at once
    and was a hectic experince.  I was using the slow WEST hardener(206)
    and was rushing like heck at the end to get it in the press as it was
    starting to set.
    
    I also have a test stab being pressed with the  glass/kevlar I layed up
    on the glass pane last week.
    
    I will never use 1/32" balsa again, it is a pain in the a**.  The
    thickness of the sheets is too variable.  Obechi seems a much better
    choice.
    
    I will report tommorow on the outcome of the above.
    
    The pink foam stab I pressed with 1/32" balsa and carbon trailing edge
    came out beautiful!  I added a balsa leading edge and tips with Elmer's
    white glue and then sanded to profile 1 hour later.  Which leads to a
    question which I am sure there is a good answer to - Why not use the
    Elmer's glue to stick the obechi or balsa or 1/64" ply sheeting to 
    your cores?  It is cheap, non-toxic, and spreads our beautifully.
    
    
                                                     Thanks,
    
                                                     Jim
     

The white Elmer's glue will soften with moisture and/or heat. You can do 
a very nice job with the yellow woodworkers glue which isn't as bad. 
Some of these glues need to evaporate or be exposed to the air to dry. 
The epoxy will cure regardless by chemical reaction. (and in a specific 
time as well)

The two layers separated by the 1x2 really make it a rigid surface. I 
don't see any problems with this deforming with a couple hundred pounds 
(me) pressure applied.

One thing I've learned when doing the wings. If you're going to use 
something multiple times, the time you spend on jigs will be well worth 
it in the long run.

Another thing I've found useful in the shop is a 33 gallon Rubbermaid 
trash can. This stands at about waist height and with a board over it can 
make a nice temporary work surface. I regularly use it on projects were I 
need to walk around the work to do things on multiple sides. The press 
rests on it nicely and is at a good height for tightening all eight nuts 
once set up. Plus it's a good place to toss trash or carve to shape over.

    Re: -2
    
    The reason I ask about using Elmer's glue is because it is routinely
    used to glue wood(balsa,obechi,basswood, etc) leading edges and 
    wingtips to obechi and balsa sheeted wings.  I appears to work 
    in this application where surface area is limited.
    
    All I can think is the water base of the Elmer's glue weakens the 
    wood sheeting or traps moisture in the foam or somethinf like that.
    
    I will do a test panel using this method and report.
    
    
                                                   Regards,
    
                                                   Jim

The toughest thing is going to be telling when the center of the sheeted 
surface is dry. I think the water content is going to wreak havoc with the 
"flatness" of your sheeting and you're going to see some major ripples. 
Please let us know what you test panel shows (you might want to cut into 
it after a few days and see just how dry some of the inner glue really is.

I got my wing press finished up over the weekend. Yesterday I got set up 
and did a dry run to make sure everything would work. Tonight I'll press 
a set of Alcyone 2M cores. One of the things I realized/discovered is 
that I need to put nuts and washers on both sides of each layer. First 
to allow unstacking from the second side and second to keep successive 
layers from further compressing the initial layer. 

Last night I cut the obechi which I'm going to use to sheet these cores.
The guy from Kennedy Composites told me about a small rotary cutter (like
a pizza cutter) used in cutting quilting cloth. I think the name he said 
was Olfa. I picked one up ($16 at a discount store!) and gave it a try. It
worked great and allowed me to roll it along a metal ruler to cut the 
sheets to size. We have a glass table out on our deck and that turned 
out to be the perfect surface to cut this against.

Tonight, those cores go in the press

    >>We have a glass table out on our deck and that turned 
    >>out to be the perfect surface to cut this against.
    
    I must say that glass is a great surface to work off. I have a small
    mirror that I use to cut trim on and cut out masks for painting. Don't
    know what I would do without it.
    
    Eric.
    

Yeah, my wife wasn't home or I would have been in deep sneakers. I don't 
think she'd take to kindly to me laying up the kevlar sheeting on her 
pride and joy 8^) I'll have to buy a piece or find a cheap mirror in the 
future.

Last night was the first time I used my press. It seemed to work well once 
I got things going. My gallon bottle of epoxy had solidified so I spent an 
hour and a half with it in a hot water bath "melting". It did but that got 
me a late (11:45pm) start.

I mixed enough epoxy for two panels but the extra warmth kicked it off too 
soon so I needed to remix some for the second panel. The press worked well 
and I was able to set it up but it sure took a long time to spin the 8 
keeper nuts down 30" of 1/4-20 threaded rod. I'm using 24 hour epoxy but 
I'll probably leave them in there until friday night to be sure. I'll 
report back on monday on how things went.

One of the hassles was having to clean up. (along with not having much 
alcohol left) The mixing cups I use have marks for measuring. I think what 
I'm going to do is buy a package of paper cups and measure ounces into it 
and mark the levels. Then I'll take a second cup and slip it over the 
outside and cut slits in it at the marks on the first cup. This way I can 
mark new cups through the slits and not have to worry about having 
graduated cups and can toss out the leftovers in the mixing cup. Cleanup 
was lretty involved and took quite a bit of time. It was 1:30am before I 
got out of the shop (and 3:30 before I unwound enough to sleep). I did 
sleep better knowing I didn't have to worry about a vacuum leak or faulty 
vacuum switch failing unattended. I don't think the nuts will all back off 
on their own 8^)

    What kind of epoxy are you using?  I've never had Enviro-tex solidify
    or kick off quickly.  I can see where spinning nuts on long rods could
    be a drag.  Could you slot the press boards so that the rods could be
    removed without unthreading the nuts all the way?  Washers could bridge
    the slots.
    
    Charlie
    

Yup, a one gallon kit of Enviro-Tex Lite. Only the white component 
solidified. The yellow part was fine. It had been about 3-4 months 
since I last used it and it's stored in a cabinet in my cool basement.

The slots would probably work fine but the problem would be keeping the 
washers up while slipping the board in. The washers and nuts were only a 
problem in time. The kicking off of the "pot" was due to the amount of 
time I took adjusting the core in the beds. I was probably pretty close 
on the time anyway. All I did was drop the intermediate board in place 
and turned back to the "pot"-cicle. I think it was a combination of 
preheating the white part, mixing 4oz and using less than one initially, 
taking my time scrapping the excess off the obechi, and cleaning up my
"wet out" area before turning to start the next panel. Read: I took too 
long to get back to the "pot". Doing one layer at a time and using 
disposable cups for mixing should cut the time down significantly.

    Another trick is to cool the pot to keep it from kicking.  I've taken
    quite a while with Enviro-tex and never had it kick on me though.  I
    usually thin with alcohol which seems to slow down the cure in the pot.
    You could use tape or rubber bands to hold the washers up.  I just use
    weights on my layups.
    
    Charlie
    

Yeah, I was using it straight and the 3+oz mass in the cup generated quite 
a bit of internal heat (which I think is why it kicked rather than a side 
effect of it kicking). In talking to Tom up at Tom's Hobby Korner, I got 
the impression that the alcohol would reduce the strength.

My best bet is to just mix enough for one application at a time.

The nice part of my press is that the washers and nuts under the layer (each 
layer is locker in place from both sides) keep it from applying too much 
pressure as well so I can put extra layers on top without effectively adding 
weight. The locked together layers are sturdy enough for it to be moved out 
of the way (it's on the floor in a corner at the moment) without having to 
worry about things shifting and it's able to press 100-200 pounds without 
WEIGHING 100-200 pounds 8^) I also hope to be able to flip it over to remove 
the bottom layer without having to disturb the other layers. Sort of as a 
FIFO queue. I should be able to stack 6 layers on the 36" rods and all it 
would take is another 8 pieces of rod to keep the process going when the 
last layer is placed on top (so the new layer wouldn't block taking stuff 
off the bottom)

    The alcolol evaporates quickly when you spread it out thin.  I've used
    it plenty with no ill effects.  It does keep the pot from turning into
    a solid because it doesn't evaporate.  This could scare people into
    thinking that the alcolol weakens the bond but I don't think it does.
    
    Charlie
    

The first set of wings came out of the press friday night. Simply incredible.
Arrow straight and perfect. I'm dead on with the incidence meter end to end.
4 more sets went in over the weekend. I'm getting faster at preping the stuff 
and getting them into the press.

    RE: -1
    
    Jim,
    
    Congrats on the successful wings.  Did you use any spar structure?
    Did you happen to weigh them?
    
                                        
                                                           Regards,
    
                                                           Jim
    
    
                                                        

obechi covered, 30" panels, 10" -> 7" without 1/4" LE, 18" 1"x3/8" balsa 
spar, 2 pieces 1"x24" CF (top and bottom) and 2" fiberglass tape on the 
trailing edge. One came in at 155 grams and the other at 170 grams. The 
heavier panel is the one where the epoxy had started to kick.

I've got another three sets in the press along with the tiplets so I'll 
let you know how consistant I end up being. 1/2oz of alcohol to 2oz of 
epoxy seemed to work well and give me something that wasn't too runny.

Well, I finally got around to taking the tiplets out of the press last 
night. The one set that I trimmed and weighed came in at 25 and 26 grams. 
So, without leading edges, balsa tips, fiberglass joint reinforcement, 
13.25oz total. I should be able to make the 18oz range with 4 s133 servos.

I've got three more sets waiting to be trimmed so I might be able to do 
better on future sets. The thickening epoxy on that one panel cost me 
almost an ounce!

>The thickening epoxy on that one panel cost me almost an ounce!

~28 grams = 1oz

15 gram difference in inboard panels so I'll need to weight the opposite 
tip (further out so less weight) so not quite an ounce total but better 
than half an ounce difference is significant.

    I found that you can use any amount of epoxy to sheet wings!  I've done
    some where I used more than necessary - and all it does is add weight. 
    I've never ever used too little!  Next time I plan to try applying the
    epoxy with a sponge roller instead of pouring it on and scraping the
    excess off.  (I'll still scrape any excess off but hopefully with less
    soaking into the soft balsa.
    
    Charlie
    

    Jim,
    
       How do you regulate how much pressure is applied to the core?
    I have heard of using spacer blocks, but these would need to be 
    very accurately cut.  
    
    I thought of using a torque wrench, but not owning one, I used the
    "that feels about right method", and it seemed to work OK.
    
    Sounds like your kit buying days are coming to a close,
    hope to be there soon myself.
    
    
    BTW - I found the Race Cat plan Hartmut had given me last year.  It
    was in my Multiplex Fiesta Box(how it got there I don't know).  
    I hope to cut a set of cores and build it when I get time.  It would be
    nice to make a plug and do a fiberglass fuselage for this ship. The
    panels are 400mm(15.8") with trailing edge taper.  I really want this
    kind of a plane(don't know if I can fly it!).  Seems like a lot of fun
    and a lot less $$$$ than the F3E circus(7 cells vs 27 cells, 30 amp
    speed control vs 100 amp speed control, no computer mixing, etc).
    
    
    
                                                     Regards,
    
                                                     Jim             
     

The hard part for me in applying it was over the fiberglass trailing edge 
reinforcement (remember these are razor trailing edges) and the CF over 
the spars. I used a bit too much and it did seep through some. Due to the 
"textured" surface of these materials, scrapping off the excess was a bit 
difficult but I passed it off to added strength where it would do the most 
useful. The obechi adds a lot more strength than the balsa I used on my 
original. These wings should really stand up to the winch (and I've got 
the winch to test them 8^)

I can't wait to see how the open and standard class sets come out.

Re: .95

Hartmut is sending me a set of plans as well when he sends my Jet fuselage. 
My intent is to use it as an initial attempt at fiberglass fuselage making. 
I figure the Race Cat is small enough that it should be a managable 
plug/mold/fuselage. My intent is to lay it up out of kevlar to help with 
the fuselage side splitting on grabbing a wing tip on landing. The Jet 
fuselage will be for my Astro 25 and should be a nice performing ship.
I'll let you know when I get some Race Cat fuselages in production (should 
be late fall). Maybe you can QA one for me?

I didn't want to use spacer blocks due to the differing heights of my foam 
blanks (the initial stock varies quite a bit). My press layers weigh 25-40 
pounds each so I just slide them down onto the cores, readjust everything 
into place and then hand tighten all the nuts. Then I go around and measure 
the thickness and crank each one 1-2 turns. Then I crank the lower nuts up 
from "inside" the sandwich to lock the plate in place. This prevents future 
layers from applying additional pressure. It's worked so far...

>    Sounds like your kit buying days are coming to a close,
>    hope to be there soon myself.

I know what you meant but it's probably more due to the lack of time to 
build for myself 8^(

    RE: .94
    
    I have read that some people are using West Systems Colloidal Silica
    to thicken the laminating resin.  The resulting "paste" is thicker
    and lighter than an equivalent amount of pure epoxy. 
    
    Supposedly the Silica does not weaken the resin like microballons,
    something to do with the "molecules lining up".  This "paste" does
    not soak into the wood as much.
    
    A big can of the Colloidal Silica is less than $5.
    
    Ed Slegers talks about using a credit card with teeth cut in, to
    spread the epoxy out in 1/8" rows along the length of the sheeting.
    
    The Freudenthaler built wing I received did not use these methods,
    because I noticed a slight amount of "bleed through".  I personally
    would rather be a little heavy and not have to deal with delamination.
    
    
                                                       Regards,
    
                                                       Jim
    
    
    
    

>    A big can of the Colloidal Silica is less than $5.

got one coming from FibreGlast (half gallon 8^)

>    Ed Slegers talks about using a credit card with teeth cut in, to
>    spread the epoxy out in 1/8" rows along the length of the sheeting.
 
I haven't heard of them THAT close together but, yes, you do need to leave 
lines if you thicken it. I'm concerned about the "spreadability" issues but 
I'll give it a try and and decide from there. I have a short spatula that I 
use. It has the bevel on the top edge so it scrapes off the excess epoxy 
quite well when pushed over the surface. I was hesitant to use obechi 
initially but the benefits far outweigh the hassles. Using the rotary (quilt)
cutter to size the sheets was a big win
   
>  I personally
>    would rather be a little heavy and not have to deal with delamination.

Those are my feelings as well but I know there are people out there that 
want minimum weight regardless of cost. They'll trash a wing rather than 
adding the weight of a minor repair. I love following them to the trash 
bin 8^) I've done some stupid things that have crashed my airplanes but 
even with hitting the backstop with my Alcyone 2M, the wing survived intact.

My understanding is that the bleedthru is invisible once you put a coat of 
water based urathane on so I'm not too concerned.

    Delamination was a big problem for the west coast guys in '82 due to
    the heat and the thin amounts of epoxy that they were using. I know
    that they began sealing the foam first, as a cure, but what they used I
    do not know.
    
    I hope to be at a slope race in Torry Pines, CA, this Sunday. I'll ask
    around about wing techniques. I may fly/race if they can find a mode-1 
    radio for me.
    
    Regards,
    
    E.
    

    Ref -.2 In my former life I used foam 3" paint rollers to spread the
    epoxy stuff. It went on fast and even. Don't use the fluffy ones!.
     
    I also used .6 oz cloth inside the skins of my racing wings as a
    "binder" between the skin and the foam. The cloth was applied to the
    inside of the skins could be "credit card scraped" to remove excess
    resin.
    
    Enough flashbacks.......
    
    E.
                       

    Jim, just a thought on applying epoxy to fiberglas.  In building home
    built airplanes, a very thin coat of epoxy is applied to the raw
    surface and the first fiberglas material is place on top of this and
    then "stippled" (use a 4" x 4" cheap paint brush and stipple the end of
    the bruch on the fiberglas to raise the epoxy through the cloth) then
    lightly use brush strokes to keep working the expoy into the cloth. 
    Then use a a rubber or plastic "weegie" to wipe off all excess epoxy. 
    Next, put the next sheet of fiberglas on the surface without any
    additional expxy and stipple this until the second surface is wet (a
    little epoxy may be needed if the second layer of cloth appears to be
    dry.  Then the above process is repeated.
    
    Regards,
    
    Ollie
           

I've heard of the stipple method being used when laying up fuselages. The 
stipple action of the brush also helps remove any air bubbles. There really 
isn't a lot of fiberglass involved. I use a 2" ribbon on the traling edge 
and some of that comes off when trimmed. The 2.9oz CF over the spar is only 
1" wide and I don't mind a little extra epoxy there. I might use the silica 
there to help fill in and lighten this bond. I've heard of spackle being 
used as a white foam filler. I can't wait to get a chance to try the glass 
plate kevlar layup over some of these cores but I'm already behind schedule 
on this production run.

Eric, any tips you can glean from the racers will be appreciated. They 
aren't as concerned about weight so I'll probably be selective about using 
them but it's always good to hear what works for others. I've used graduated 
triangles of light glass between the skins and cores in the past and it 
really does add strength. With the silica/epoxy mix it shouldn't cost quite 
as much weight.

    re: -1
    
    Boy, Eric I do envy you!  I would love to see a real slope race with
    all the equipment and guys that actually like gliders!  Silent flight
    at 100 mph is my thing!  Please post a report if you go.
    
    
    I think delamination becomes a much greater concern when used with closed
    cell foam(blue/pink) and composite fabrics for sheeting.  Composite
    Structure Technology Inc. is actually selling a tool($75-ouch!) for
    "pin holing" foam to allow the epoxy to adhere better.
    
    This is the nice part of using white foam and wood sheeting.  In
    addition to being simpler(no vacuum bagging) it appears that
    delamination is not a problem.
    
    
                                                   Regards,
    
                                                   Jim  
    

    Well sounds like 'ye have a great way of using a credit card and not
    getting billed for it....
    
    Ooopps card over the limit....time to do some wings !
    
    8-)
    
    Alt-E. 
    
    PS: Sounds like some great progress on the wings.
    

That's probably the only hobby use my wife would let me use the cards 
for 8^)

    mine too. I can see the bonus points adding up. Come to think of it ...
    now if she could only use the card in the same way 8-)
    
    Alt-E.

Well, I took another three sets of wings out of my press last night. I found 
that the thinned epoxy does flow better and seems to be lighter (I haven't 
trimmed and weighed these panels yet) but there was more bleed thru. The Silica 
hasn't arrived yet so we'll see how that improves things next week.

I also found that I need to be a bit more careful about the pressure I use. One 
of the panels shows a spar bump due to the press compressing the surrounding 
foam more than the spar. It was slight enough that I was able to level it out 
by sanding the sheeting slightly but it does reinforce the point about 
regulating the pressure.

I did find that the trailing edge of the previous panels did sand to a nice 
sharp stiff edge. The 2" 9oz glass tape really helps the strength. It holds the 
undercamber quite nicely.

20-30 panels and I should have it down pat 8^) This really is similar to the
foam cutting startup where I needed to "tune" the process over the first x 
cores. I know that the struggles I'm having now will pay off in the long run 
and the quality will go from very good to excellent. The quality is already 
better than my balsa/vacuum bag attempts of the past.

I've found out a few more things about sheeting with the press this weekend.

First a few common sense things That I "discovered" over the long weekend.

Don't work when overtired. If you've put in the time to do it right why take 
the chance you'll screw up? Make sure your hands don't have epoxy on them and 
that your board/bench doesn't either. I used a piece of plywood over my trash 
can as a surface to squeegee the epoxy onto the skins and I covered it with 
freezer paper (with the plastic coating on one side) and this made a nice, 
clean, disposable surface. In between panels I'd wipe the surface with an 
alcohol rag to clear off the sticky drips. I did get a little epoxy on the
outside of the beds and that did make them stick (slightly) to the press.

Silica:

Well, my package from FibreGlast arrived friday so I decided to give it a try. 
Over the course of the weekend I found that 2oz of epoxy, 1/2 an ounce of 
alcohol and about 1/2 fluid ounce of silica made a good working mixture that 
didn't bled through and wasn't so pasty that you couldn't spread it. I use a 
pancake spatula (2"x3" blade with a short handle at 30 degrees) for spreading 
and scraping and I find that 2oz+ mix is good for a 48" panel with some minor 
(1/2oz) waste. 

Mixing:

I mix my epoxy in clear plastic tumblers ("on the rocks" style with the
big open mouth) and I have a single one that I cut slots in. Initially I 
measured 1oz into a glass. I slipped a second glass on the outside and marked 
the location (do it on a level surface) on the outside. Then I added a second 
ounce and marked that location as well (I use a 1 to 1 epoxy). I then drilled 
holes in the marked cup and used a marker through the holes to mark cups for 
future use. Much cheaper than trying to find/clean/buy premarked cups.

Even with the 1/32" balsa there was very little bled through with the silica 
mixed in. I made sets of each size for my personal use (as spares in case I 
screwed a set up) and I managed to get all of them to come out fine. I'll weigh 
the new sets tonight as I'm sorting them out.

I did get cranking on the stabs when it was time to press them. I managed to do 
6 sets of stabs in a single layer in the press with one 2oz batch of epoxy. You 
need to precut everything and have it laid out but they went together like 
buttering toast for breakfast and they came out great. I used 1" wide glass 
tape for the stabs and  they seem almost as light as my built up ones. (again, 
have to weigh and compare tonight) I was also able to do 3 sets of tiplets per 
layer as a single batch. It takes a while to clamp things in the press so it 
saves time to do multiple parts on a single layer.

The 1/32 balsa covered stabs showed the spar locations after pressing. I was 
amazed at how quickly this disappeared with some light block sanding. Sanding 
everything with 600 grit paper after cutting to size really finishes them off 
nicely.

A bottle of foam safe CA is a worthwhile investment in making things keep going. 
Having multiple things going at once allows time for glue/spackle to dry. CAing 
the spars together and then gluing them in with a good buttering of 30 minute 
epoxy seems to have worked well. I'll have to flight test my wings to know for 
sure. The Jarmac table saw paid for itself in the wing trimming and the vertical 
grain balsa trimming.

Time consuming things:

Gluing spars into the cores (stabs and wings)

Cutting the freezer paper to size for between the core and bed.

Taping and untaping the joints (balsa only) and trailing edges

Over the last couple of nights I've been fiddling with the router on a 
few wings and have found it to be the perfect tool for some of the stuff. 
The wings I shipped out had to have the wing surfaces routed along the 
hinge line and I did it with a metal ruler on either side of the slot. 
First I tried routing one entire side and then going back down the other. 
This worked "ok" when you do the trailing edge side first but a better 
way is to do it in 2-3" sections and clean up both sides as you go. Last 
night I redid my servo installation in my old Alcyone wings. I pulled 
the servos one at a time and filled the cavity with scrap foam and routed 
out a tight fitting cavity as deep as the servo. This made for a much 
nicer/tighter installation and if done on a new wing, would just require 
some tape over the servo to hold it in place/seal it.

The Dremel router attachment really seems worth it. Another case of how 
did I ever do without it.

    Jim,
    
       I routed out the ailerons on my Surprise II using the dremel
    tool with router attachment.  I had a hard time doing it.  Could
    you further explain the method you used.  I routed through the
    bottom of the wing using a single straight edge secured near the middle
    of the wing.
    
    What happened is the router "walked" into the aileron and the
    initial plunge into the wing bottom was quite oval due to the 
    undercambered(RG15) foil.
    
    Thanks for any additional info.  Did you get a chance to look over
    the race cat plan?
    
    
                                                       Regards,
    
                                                       Jim
    

Well, I'll explain both operations in a little more detail since it sounds 
like you had problems with both.

First, to cut the aileron hingeline out I used two metal rulers. I taped the 
first one at the root of the wing and extended it along the wing and taped 
the other end down (it overhung the tip). Then I used a couple of small spacer 
pieces of 1/4" (both surfaces faced with 1/8" balsa) along the side of the 
ruler and added the second ruler, taping the end of this one to the tip. I 
then taped across the rulers to hold them together with the spacers between. 
Now about 1" back fronm the end of the cut I plinged the router through the 
wing and it road on the rulers while I did the cut. Like I said in the 
previous note, I would trim one side of the cutout for 2-3" and then go back 
along the other side and clean up that edge. By always working near an 
attached edge, you don't "bow out" the aileron with the pressure against the 
straight edge. Keep in mind that the edge of the bit is riding on the ruler, 
not the plastic base of the router. Since my ailerons are tapered, I couldn't
use their attachement to ride along the trailing edge, I did it freehand within 
the limits of the two rulers. I adjust the bit (which goes all the way through
the wing) so that the smooth part is what rides on the ruler. Remember that 
the bit is exposed below the wing when doing it. I cut mine (SD7037) from the 
bottom of the panels.

To cut out the servo cavity I just mark around the servo where I want to put 
it and set the bit depth for the width of the servo plus a plywood floor and 
then plunge into the center of the marked area and carefully work my way out 
to the outline. I use two hands on the router and I run it at top speed. For 
this I had the wing weighted down in the core bed so it wouldn't move.

Clear enough?

Haven't done anything with the Race Cat yet. I hope to have a chance to fiddle 
with it next week. I'd like to get the wooden version going soon so I can then 
use it as a plug for the mold. I want to flight test it before "casting it in 
stone" 8^)

    The router would be good for retract wells etc.

The problem I see with retract wells is depth (the bit is only about 1" of 
cutting area and not a very long shank) and keeping it flat to the surface. 
You could keep it flat by cutting through the core bed as well as the wing 
but that only makes the depth issue larger. 1/8" router bits aren't that 
common.

Finally weighed a few of the other panels. After the initial set that was 155 
and 170 grams, I seemed to be 2-3 grams around 140.

    I received the literature from Rich Spicer last night. If anyone wants
    a copy send me mail. There are about eight different gliders, all of
    which are tantilizingly "cool".
    
    Synergy, Genesis, Nova etc. I have seen all of them fly and they are
    real performers. Hollow core wings, CF everywhere....Hmmmmmmmmm
    
    
    E.

    Could it be that the Evil one is getting the glider bug again??????
    
    Na......couldn't be.
    
    On the other hand......
    
    No.....my mind just won't accept such a radical idea.
    
    Than again, the local glider circuit is virgin territory yet to suffer
    the delights/despair of the "Evil syndrome".
    
    Na......I just can't imagine it.

    All it would take is $485.00, I have everything else!.
    
    EVL-1
    
    

Talked to Burt at Kennedy Composites earlier in the week (needed to 
order more stuff) and he said something that I'm questioning a little 
bit. He claimed that the typical kevlar/glass fuselage is strong in 
tension but weak in compression BECAUSE the woven cloth is already in 
a compression failure mode (non-straight fibers) so his recommendation 
was to use a tow type of material for tail boom reinforcing since the 
fibers are straight and would provide good tension and compression 
strength.

I use kevlar tape simply because of the convenience but wonder if I 
should go to some of the CF tow that is bonded to a carrier but has the 
fibers unidirectional instead. I would imagine that tow would allow you 
to use less material for similar strength.

The other question on the table is when coating obechi sheeting for 
pressing/bagging and using a notched scraper, in which direction should 
you position the lines of epoxy? Spanwise? Chordwise? Diagonal? Wavy? I 
would think you would want some cross-grain component but how much is 
reasonable?

>bit. He claimed that the typical kevlar/glass fuselage is strong in 
>tension but weak in compression BECAUSE the woven cloth is already in 
>a compression failure mode (non-straight fibers) so his recommendation 
>was to use a tow type of material for tail boom reinforcing since the 
>fibers are straight and would provide good tension and compression 
>strength.

I've heard that before and believe it.  But the tail almost always
breaks on the top in compression so tow on the top makes the most since
to me.  I was warned that the Hobie Hawk had failure modes in the tail
so I put carbon tow on the top and sides.  What a time I had trying
to make it invisible with resin and filler - but I did.

Most of the older Dodgson designs are taco shell layout and with the
wood top piece on the top of the tail boom they have a lot of strength
to resist compression on javelin landings.  But what happens is the whole
mess flexes and the top wood breaks along the seems of the glass - my
Lovesong did this twice.  In this case it looks like the right way to
build it would be to have wrapped the tail boom after the top is put
on the Taco shell - but then again we are talking some serious weight.

When you cartwheel the stress on the tail boom is sideways and I have
cartwheeled the Hobie Hawk a lot - no problems so far.

In some earlier note there was talk that the problem goes away if you
fill the tail with foam.

About the scraping epoxy direction.  Ask someone at Color Tile :-)

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

But tile doesn't have grain (I've done about 1000 sq ft of tile as well 
8^)

Kay, why don't you just glass the top of the taco shell fuselage as well? 
Then you could delete the wood and voila! You've got a one piece fuselage 
just like a non-Dodgeson ship 8^)

Re Foam Filled

Yeah, I've heard this as well. The compression failure will deform the 
surface flat before folding over and the foam is supposed to keep the 
boom in a round cross section which is stronger. This is why you want 
to go with a round boom rather than oval (flat spots on the sides) I 
would think that an egg shape would be good since you'd have the sharper 
radius on the top (more strength) and you could reinforce the sides 
easily while in the mold. The round cross section is still supposed to 
be the strongest for uniform materials. With a molded fuselage you'll 
have the overlap seam on the top and bottom to reinforce it there.

Picked up some of the gray at lunch. It went up recently, $10.79 per 
sheet.

>But tile doesn't have grain (I've done about 1000 sq ft of tile as well 
>8^)

Try laying some down at random and see if you wife don't kill you!

>Kay, why don't you just glass the top of the taco shell fuselage as well? 
>Then you could delete the wood and voila! You've got a one piece fuselage 
>just like a non-Dodgeson ship 8^)

On Dodgson kits you do glass the top over the wood deck that gets placed
on top of the taco shell boom.  Since I'm in the middle of a Pivot-Plus
fuselage right now...

There are advantages to taco shells.  You install push rods and the guides
out in the open air and seal it all up later.  

From a manufactures point they are handy because you can stack them inside
each other and save a ton of space storing completed fuselages.

In the case of building the Lovesong - after many many many hours
of construction the rear deck and top nose of the taco shell fuselage
was lost in the noise.

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

>>[...] and seal it all up later.  

Couldn't resist:

But we do it once less than you 8^)

Glad to hear the Pivot Plus is on the bench. I'll be interested in seeing 
how it comes out. I almost bought a Sig Samuri last year at the WRAMS 
show but the building queue was (and still is) too deep. I've seen them 
under $100 since (show special was $142)...

I've been doing some Quickee 500 wings recently and have a few 
observations to pass along.

I'm using a 3M water-based contact adhesive (at the customer's request)
and it's really stood up well. One of the problems using it, though, is
that the obechi absorbs a lot of the water and releases it slower so the
sheeting initially curls adhesive side out but as it dries the adhesive 
shrinks and the outer surface expands so the curl reverses and finally 
when the obechi gives up the water (which has now travelled through the 
entire sheet to get out) it lays flat. The can says that the adhesive 
dries in 30 minutes but the obechi takes 3-4 hours to pass the water.
A nice feature of this adhesive is that it's aqua colored so you can see
where you've put it. I'm using a roller to apply it and it's worked out 
real well. This has been the major bottleneck for the procedure. The 
wings are coated on both sides and then stabbed onto nails stuck through 
a board. Since there will be tip plates installed before shipping, this 
hole doesn't show.

Reinforcement on these wings is a 2" strip of 4.5oz carbon fiber inside 
the bottom sheeting. This is applied with foam safe CA to the sheeting 
before the contact adhesive is applied. I actually did the entire batch 
of wings ahead of time.

I attach the leading and trailing edges with Titebond and then finish 
sand them flush with 60 grit paper on a power sander. This gives the 
obechi a nice finish and goes pretty fast (without really cutting into 
the obechi too much). I was really surprised how little the 60 grit cut
the obechi

Another operation is to install the landing gear mount. This is a 12" 
strip of hardwood put in after the sheeting. I use my Dremel router and 
a jig I made to cut the outline out and then I break out the wood and 
attached foam, remove the jig, and rout the resulting hole to the proper 
depth (which causes the non-cutting portion of the bit to ride on the 
obechi edge). The blocks are held in place with a combination of epoxy 
and either micro balloons or collodial silica mixed to a peanut butter 
consistancy.

One sample wing I did with epoxy instead of the contact adhesive was 
destructively tested at 300 pounds when supported by the tips. On a 
typical 3 pound Quickee, this is 100Gs! The CF strip is the only 
structure (tension) and the top sheeting is workig with it in compression.
The contact adhesive wings are supposed to be in the 50G range. Typical
flight loads are 20-30Gs.

I didn't weigh the individual wings but 14 of them packed in their beds 
and surrounded by foam in a 52"x18"x18" box weighed 22 pounds so I think 
it's reasonable to estimate the 50"x9" chord wings with a thickness of 
1 3/16" weigh about a pound a piece. Really pretty reasonable, I think.