Conference vmszoo::rc

Just what is this carbon fiber tape, where do you get it, and how much does it 
cost?

Dave

>Just what is this carbon fiber tape, 

It is some black (carbon colored) stuff that feels like Fiberglas
and comes in rolls that look slightly like tape but it has no sticky stuff
on it - it is only rolled up for convenience.  It has a very high strength
to weight ratio so a lot of glider guiders use it to reinforce their wings
so that they won't fold on a high start.

>where do you get it, 

Maybe at your local hobby shop but Tower Hobby has it for sure.

>and how much does it cost?

Approximately $5.00-$10.00 for enough for 3-4 wings.  It comes in various
widths but you can slice it with an Exacto knife.  Never used it myself
but Kevin Ladd has and he added his carbon fiber to some old order I sent
in to Tower so I got to touch and feel the stuff.  There are warnings about
the fibers being dangerous and to work with caution.

Along those same lines I would like to ask the same questions about 
Kevlar?  

Does it look like fish line or can you get flat tape?
Can you CA it?
Where do you buy it?
How much does it cost?

Bye          --+--
Kay R. Fisher  |
---------------O---------------
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        I've never seen pure Kevlar tape, the way I've seen graphite tape.
        I do have some stuff that is about 90% Kevlar, 10% glass. It comes
        in 1 foot width as long as you want it. I wouldn't use it for wing
        spars thou, I'd stick with the graphite. 
        
        Graphite is stiffer than kevlar, bit more brittle. Kevlar is
        tougher ("bullet-proof"), but not quite as stiff. Since you mostly
        want stiffness in a wing, use graphite there. Save Kevlar for the
        fuselage where it is constantly getting dorked and cracking. 
        
        These days I get most of my composite materials from Aircraft
        Spruce in California. They are in the homebuilt (as in EAA)
        market, but most of their stuff is great for modellers, and they
        don't mind selling very small quantities of most stuff. Catalog is
        $5, and I think they have an 800 number. There is an outfit called
        Aerospace Composites (Irvine, CA, no phone#) advertizing in MA
        that carries some of this stuff, but at higher prices. 

        If anyone finds a source of kevlar tow (like the stuff Sullivan
        plastic coats for its control line) that doesn't cost a fortune,
        please let me know.

>       I've never seen pure Kevlar tape, the way I've seen graphite tape.
 
    Umm, not to seem dense, but that implies that you have seen pure
    graphite tape.  Might make a great lubricant, but I wouldn't think
    it would hold together very well.  On the other hand, maybe I'm
    just out of it....
    
    WIllie
    

How do you apply the graphite/carbon fiber tape to the spars? Do you cut it to
the width of the spar and CA it to the bottom surface of the spar? How about the
leading and trailing edges? What are the safety/health hazards? Do you use it 
for the full span of the wing?

Dave

    One carbon-fiber hazard- them fibers conduct electricity!  
    
    I have seen reports concerning carbon-fiber induced short circuits
    in computers, transmitters, and motors.  When the fibers are cut
    or sawn, they often get into the air and float around for days.
    If they get into a motor commutator, radio transmitter, or computer,
    they will often short something important out, either making the
    case "live" or actually shorting V++ to V--.  The fibers aren't
    as conductive as copper- but they are more conductive than cast
    iron.
    
    Moral: Cut fiber outdoors if you can, never saw it indoors, and
    especially never saw it indoors with your moto-tool :-)
    
    
		\__    		-Bill
	  {((___O===--0'         Yerazunis
    

        I've been using the carbon fibers on HLGs and model rockets, so my
        needs may be different from yours. The techniques should be the
        same, thou, just differences in scale. Cutting the carbon tape is
        the same as cutting fiberglass; sharp snips work fine. Kevlar is a
        bit more difficult; while there are special snips available, they
        are expensive, and normal tools will work, with patience. 
        
        It is easy to take a wide carbon or Kevlar tape and narrow it; it
        is just a bunch of loose strands. Pick off the amount you need,
        and slowly work thru the bundle until you have two or more pieces.
        In a similar manner, the carbon tape can be tapered at each end
        for the wing tips. On my HLGs, I do this by running my fingernail
        or a knife edge over the bundle ends several times, sort of
        combing out excess material. 
        
        I did start using CA to bond the fibers to the wood, but it is
        just too fast, and the slower is too thick to penetrate well. Even
        applying with fingers didn't give me good results. You need to
        totally wet all the fibers to get maximum strength, and then
        squeegee out any excess adhesive to remove excess weight. I just
        can't do it fast enough with CA. Results are messy and heavy.
        
        Second try was Amberoid, thinned with acetone. This was
        recommended by Mark Drela in his Upstart Indoor HLG article. I saw
        him demonstrate this technique, and it worked ok. I did have some
        problems where the fiber would debond form the wood, so I kept
        looking. I don't think it would be suitable for RC models. 

        I finally (currently?) ended up with Safe-T-Poxy (from Aircraft
        Spruce) as the adhesive of choice. It is a 24 hour epoxy
        specifically designed for glass/carbon/Kevlar layups. It was
        developed for use on Rutan's homebuilt aircraft kits. It is thin
        enough to easilly work into the fibers. For small stuff like HLGs,
        I run the fibers thru my mixed pot of epoxy, and then work it in
        and squeegee it down with my fingers. Then I lay the strand down
        where I want it, and work the epoxy into the surface, again with
        the fingers. Kevlar is a bit harder to wet, so the Safe-T-Poxy can
        be thinned a bit with alcohol (Denatured?, Iso?). 
        
        I use Kevlar thread from Brookstone or US General, wetted in
        Safe-T-Poxy, along the leading edge of my HLGs to prevent damage.
        An RC rocket friend laminates some of the very thin (.007) carbon
        sheet or matte into his trailing edges. He just started using the
        Kevlar matte on the inside of his radio pod, and when a recent
        wing failure left his fuselage streamlining in, that section
        survived intact, while the rest was demolished. 

        Safety? Both the carbon and Kevlar are less irating then glass.
        Care should be used with any of them after curing, as small pieces
        can be very sharp, and splinter easilly. VERY painful under
        fingernails. The Safe-T-Poxy itself was developed to have much
        less skin toxicity than conventional epoxies; as I don't seem to
        have any problems I can't say it makes a difference for me. Carbon
        is conductive, as mentioned. Remember the picture in MA of the
        carbon F3B ship that met a power line? It can act as an RF shield,
        so don't put your antenna inside (or outside for that matter) a
        carbon tube. I haven't heard of anyone doing so, but it may be
        possible to use a carbon tube fuselage AS the antenna. 

        Carbon sheets are also available. These are from .007" to .035"
        thick, and already epoxied and cured. The result is a very hard
        sheet, that is very strong in one direction, but easy to crack
        along its grain, as is A grain balsa. This can be cut for spars
        and other reinforcings. Care should be used with this stuff, as
        the splinters are particularly nasty (remember the warnings about
        Boron?). These can be attached with either the epoxy or CA,
        and are great for spars.

    I used the Carbon Fiber tape that comes as a 1.5 inch wide, flat
    bundle of loose strands (like really fine hair).  I separated a
    bundle that was about as wide as the spar on my wing, and as long
    as the wing, and glued it down with CA, using a plastic bag on my
    fingertip so that I could press it down on the spar.  I was
    concearned about the wing flexing, as I said before, so what I did
    was this...  I placed the wing upside down on the working surface,
    and slightly compressed it at the center (so that it was flattened
    a little) and then, starting at one wingtip, glued the tape across
    the entire lenght of the spar.  Carbon tape is VERY flexible, but
    is almost impossible to stretch, so when the CA dried, and I
    relieved the stress on the center of the wing, the wing attempted
    to return to its original shape and put the carbon tape under
    tension.  in this way, when the plane is flying the tape is
    further stressed longitudinally.  the only way the spar can bow is
    to twist or actually compress across its top edge.  the result was
    a wing, as I said before, that is noticably less susceptable to
    bending.

    As a quick aside, I saw a thing on ESPN last night about the
    Americas Cup.  The NewZelanders have built a new boat that is very
    unique in may respects, one of which is that the entire hull is
    built from carbon fiber.  The neat thing was that, after laying
    the sheets of fiber on the mold, and curing the glue, they took
    the hull off the mold and set it right side up, the transom of the
    hull had not been installed, so you could walk into the hull from
    the rear.  They showed some guy, wearing sneakers, who ran across
    the shop floor toward the rear of the hull, jumping into the hull
    through the place where the transom would ultimately be, he SLID
    across the bottom of the hull like he was on ice !  It was
    amazing !

    I found that when using bolts on my Wots-Wot that if they were quite
    tight that they could crack the area around the bolts on the wing and
    potentially could pull through the wing bandage. The wing is joined with
    cloth and resin - but to reduced the risk of damaging the wing I used a
    piece of a carbon fiber undercarraige that I made - cut it the width of
    the fuse and drilled two holles in it. Reduces the load and allows the
    bolts to be tightened a bit more with no risk of pulling through.
    
    Regards,
    
    Eric();

formerly Note 1151.56   by MICROW::PHILLIPS 5-SEP-1991 -< What Kay was refering to in the last note... >-
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re:.55

>>1.  Lamar did a really exciting thing with his Spirit!<<

Yup, I was experimenting with the balistics characteristics of the Spirit fuse.
I had just replaced the rubber on my upstart with some I got from Dave Walters
and was "familiar" with the strength. The wind was gusting pretty good as well.

Anyway, I did a conservative launch(read: no zoom) on the first flight and got
about a 4-5 minute flight out of it. The next flight, I streched the rubber 
about 10 yards more than the first launch. Mike Pitoniak(forgive me if I spelled
your name wrong Mike), a new member of the Acton loonies, was there observing 
and chomping at the bit to get his Spirit built. I release the plane and as it's
going up I say to Mike, "I'll show you a ZOOM launch." As the plane gets close 
the apex of the launch, I push down, gain some speed, then pull up and POP! 

INCOMMING!!! INCOMMING!!! INCOMMING!!!

The fuse looks like it's heading right at another flyer who's setting up his 
plane, but luckily it lands on the other side of the road. The wing is floating
down towards Route 2(pretty busy road.) Mike offers to get the wing and I head
off in search of the impact crater. Peter (a non-DECie and the flyer that I
thought I was going to impale with the fuse) and I took off in search of the 
fuse that landed in a knee deep alfalfa patch. I brought the TX with me just in
case(but very doubtful) the radio was still working and we could hear the servos
move. We found it after about 5-10 minutes. Damage wasn't that bad considering
it had gone pretty much straight in. The fin had broken off and the front
section of the fuse had taken a good pounding. She puked her guts out as well,
with all the radio gear lying close by. Funny thing, I couldn't find any of
the lead I had in the nose to balance the ship. I plugged the battery back into
the RX and things seem to work okay. 

Now that's how NOT to do a zoom launch Mike! I got most of the repairs done last
night and should complete the repairs tonight. The Spirit is one tough plane! I
still have to check out the servos further, but they look(and sound) pretty
good so far.

-lamar
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formerly Note 1151.57 by ELMAGO::TTOMBAUGH 5-SEP-1991 
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    re .56
    
    So what was the failure mode? Does the Spirit use rubber bands or
    a nylon bolt as wing attachment ?
    Several Spirit fliers here will want to hear about this.
    
    Terry
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formerly Note 1151.58 by CSOVAX::MILLS 5-SEP-1991 
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    He used 1/4-20 nylon bolts. I'd like to hear about the failure too.
    How come you guys never sent out mail saying that your going?
    
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formerly Note 1151.59   by MICROW::PHILLIPS 5-SEP-1991   Postmortem of Spirit
--------------------------------------------------------------------------------
RE: Terry,

As George mentioned in the last reply, I use 1/4-20 nylon bolts to hold the
wing on. I ended up ripping the blocks out and believe it was due to poor
expoxy joint(the block didn't take that much of the surrounding wood with it.)
It has surrived a whole summers worth of this type launches, so I guess I've
been luck(even several winch lauches.) 

RE: George,

Sorry for not sending out mail, I never had a chance to send out mail(too many
meetings!) I'll have the plane ready for Friday, so be prepared to go then. I'll
send out mail this time. :^)

-Lamar
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formerly Note 1151.60 by CSOVAX::MILLS 5-SEP-91 I'll bet it was cracked before launch >-
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    I found when I had the bolts in my spirit I was constantly cracking
    things around where the bolt plates were. I promised myself I would
    go to rubber bands on the next good crack. One day when doing some
    touch up I noticed the block had cracked loose. But that's not what I
    had goine looking for!!. So that was it, out came the bolt down. I never
    broke a bolt once. I always cracked something. I'll bet you had a crack
    from a previous rough landing. Pulling up did not crack the block loose.
    
    Also a little off the subject. One time when I cracked up my UHU I had
    suspected I damaged my servo gears. I checked them thoroughly (so I
    thought) by holding the servo in my hand and putting some resistance on
    the arm while moving the stick. This way I thought I could feel a
    missing tooth. NOT SO. One servo had obviuos problems so I went to
    replace the gears (first time for me). I was nervous that I put the
    gears in the right place. So I opened up the other servo that passed my
    inspection. Guess what, it had more broken teeth than the one I was
    fixing.
    
    Moral, after any severe impact the only sure way to check the servos
    is to open them up and inspect by eye. At least with S133's.
    

    
    Over the weekend I did a carbon fiber/balsa lay-up to make some
    support material. Let me explain...
    
    In the new La-2 kit I'm going to build, the landing gear blocks are
    secured to the plug in wing joiner tube using light ply.  In order
    to strengthen this area without adding weight I decided to use a 
    laminated product.  This being a bydirectional carbon fiber cloth
    similar to a piece of glass cloth for center section re-enforcement.
    The CF is called "tape" and come 3" wide by whatever length you want.
    It's rather pricey at 8.00 a yard but I'm using it in a limited
    application so the cost isn't that great. Anyways, the landing gear
    plate is supported by two half ribs that run from the LE of the wing
    to the wing joiner tube.  Actually the tube passes through these ribs.
    
    I first cut an 1/8" x 3' x 24" piece of balsa sheeting into 3 1/2 x 3"
    pieces.  These were then butt glued to create a long shear web with the
    grain of the wood running 90 degrees to its' longer length.  I then
    mixed up some of the ZAP (Odorless,Ya right) finishing resin and
    applied app. a 1/2" wide bead of glue to one side of the shear web.
    This was spread over the wood and a length of the 3" wide CF tape was
    pressed gently down into the glue and onto the balsa. I used a piece of
    glass on my building table as a flat surface and covered it with wax
    paper. The glued CF/balsa lay-up was placed on this surface glue side
    down and the glue and CF process repeated. A second piece of wax paper
    was the used to protect a second piece of glass from the glue on the
    top of the lay-up.  I added about 40 lbs. of wieght and went to 
    watch the football game. The glue is supposed to set-up in two hours.
    I returned to find that the glue was only semi hardened and that it had
    bleed through the wax paper.  I peeled off the wax paper and replaced
    it with plastic wrap and put the press back together.  Four hours
    later I removed the lay-up.  It was rock solid and straight. It was
    a little rough in texture because of the plastic wrap not being
    smoothed out but the lay-up will work in my application.  To say it
    is strong is an understatement.  As a shear web it's almost
    unbreakable.  It will twist because of it's realative thinness but once
    it's glued into the foam core and the wing sheeting is applied I'm sure
    it will work better that the light ply and be stronger and lighter.
    
                                                              
    Tom