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Author Topic: Best adhesive for carbon capstrips and balsa to carbon fiber  (Read 861 times)
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PantherM100
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« on: September 21, 2020, 10:21:08 PM »

Hi Guys:
I’m new to P30 construction.  What is the
Suggested adhesive for gluing carbon fiber
Capstrips to balsa ribs and also for attaching
Various balsa parts.
Sincerely,
Jon B. Shereshaw
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PantherM100
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« Reply #1 on: September 22, 2020, 01:16:44 AM »

Hi Guys:
I’m new to P30 construction.  What is the
Suggested adhesive for gluing carbon fiber
Capstrips to balsa ribs and also for attaching
Various balsa parts to carbon fiber.
Sincerely,
Jon B. Shereshaw
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gossie
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« Reply #2 on: September 22, 2020, 01:37:30 AM »

Cyano, and PVA for wood to wood.
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USch
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« Reply #3 on: September 22, 2020, 07:41:35 AM »

The best and lightest is a fluid laminating epoxy resin like the German 285 system. It leaves you time to position the strips and held it in place with tape. Negative side is that you have to wait at least 24h for each side to let the resin polymerise.

I do always one side (upper or lower) first, applying all carbon strips at once, and then put the wing or tailplane on his building board, cover the structure with a plastic foil and a roughly cut 2mm balsa sheet. Then I pull everything down with rubber strips from old Coupe d'Hiver motors.

I also tried CA years ago but I am not able to position every strip exactly straight on the rib as you don't have time to correct anything. AND the result is definitely heavier.

Urs
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RalphS
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« Reply #4 on: September 22, 2020, 11:05:03 AM »

My method is to use thinned contact adhesive.  Lightly sand the CF but be very careful that you don't get sharp pieces of the stuff in your fingers - it hurts and the only way to get them out is to dig them out.  Paint the balsa structure with very thin dope, allow to dry and lightly sand. Put thinned contact adhesive on both surfaces and after a few minutes bond in place.  A hot iron really gets the CF to stick.  Where CF crosses CF apply a small dab of cyano on the end of a pin.  Lightly sand any projecting pieces of CF. 

I was flying my 20 year old coupe last week.  Take it out of the box and fly it. Surfaces were as flat as when it was made.  P30 wings are capped using same method.  You can use nice thin wing sections using CF capping to spars and ribs, cover with mylar. 

Enjoy the P30.  Nice class.  Agree with Urs, cyano is the work of the devil.

Ralph
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« Reply #5 on: September 22, 2020, 12:39:11 PM »

I'm with Urs on this one. One tip from Tony Mathews is to use a small piece of adhesive tape at each end of the CF strip to keep it from shifting when the strip is pulled down with a rubber band. I've used a separate rubber band for each rib, but Urs' method sounds a lot easier.

But the easiest method of all is to make one really wide rib (i.e. 3 inches) and laminate a wide piece of thin carbon on top and bottom. After the epoxy hardens, individual ribs are sliced off with a very thin, fine-toothed cut-off blade used in a small table saw. This is the method used by most of the F1ABCG etc manufactures. Ribs for tapered panels are made buy making a taped wide rib, then slicing off ribs and using every other rib for the right panel and the others for the left.

I've used this sliced-rib method for the last 10 or so years for Coupe wings and for Coupe & F1B stabs. Once you get set up, it is like slicing salami.

Louis

PS I ordered the cut-off blade from Taig and use it on my small Taig metal lathe with a home-made table.
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DerekMc
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« Reply #6 on: September 22, 2020, 01:26:16 PM »


Louis

PS I ordered the cut-off blade from Taig and use it on my small Taig metal lathe with a home-made table.

I'd love to see your setup. Do you have any pictures?  I have a TAIG lathe and would love to give your technique a try.
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Derek
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« Reply #7 on: September 22, 2020, 01:52:47 PM »

individual ribs are sliced off with a very thin, fine-toothed cut-off blade used in a small table saw.

I would advise to use a thin diamond blade which gives a much smoother cut. Personally I cut ALL balsa strip wood and anything with straight lines with diamond blades. Fine work with a Proxxon disk saw, big stuff with a professional one. For the Proxxon they have a 0,8mm thick blade which last for a lifetime, much longer than any toothed blade.

Another advantage is that you cannot hurt yourself because the clean diameter cannot grab your fingers!

Urs
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PantherM100
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« Reply #8 on: October 09, 2020, 10:39:38 PM »

Urs:
Thanks for your input.  I would like to purchase some
L285 epoxy and hardener.  I found some at Aircraft Spuce
Co.  However, they only sell in 1 gallon kits, and with shipping
The L285 epoxy system totals almost $300.
I was also looking at the “West” epoxy kits which seem a
Little less expensive.  Would you go with the “Fast” cure
Or the slow cure epoxy?
Sincerely,
Jon B. Shereshaw
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flydean1
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« Reply #9 on: October 09, 2020, 11:09:30 PM »

West is an excellent system.  Generally you want the thinnest and slowest curing time you can stand.  If like URS, and can jig things up to cure over night, that is the best.  West produces at least 4 hardeners from fairly fast, to 24 hours.  Even the quickest cure is better than CA.  You want the thinnest coat on the joint as well which is fairly easy with West.

I always use the West pumps to ensure I mix the correct amount, and I keep them capped with "Little Red Caps" from Ace Hardware.  They are also my go-to for tank bladders.
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« Reply #10 on: October 10, 2020, 07:31:43 AM »

Jon

I've been using US Composites 635 Thin resin system for the last 10 or 12 years. There 2:1 Slow resin gives plenty of working time. I vacuum bag and heat cure using an inverted foam box and hair drier set over the vacuum bag. The finished carbon fiber has a good metallic ring.

They sell the resin in kits (resin & hardener) in various sizes. The smallest kit is 16oz of resin & 8oz hardener for $17. The next size up is a quart of resin and 16oz of hardener for $25.75. For these smaller sizes shipping is very reasonable since it avoids the extra government hazmat weight restrictions. The sell 2:1 pump sets, which I find useful for filing the small spout-top bottles. I mix by weight, not volume.

They also sell West Systems and might offer you some saving on shipping if you order smaller sizes.

In addition, they offer fiberglas and CF in a variety of types. But their selection is not as extensive as CST.

Louis
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Tmat
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« Reply #11 on: October 10, 2020, 02:04:48 PM »

I use pre-cured carbon sheet which I strip into suitable strips on a sheet of glass.
Then I apply using 3M DP-460 epoxy adhesive (it is a pure adhesive, not a laminating resin).
I apply all the cap strips for a panel at once (top and bottom) and use little strips of tape as "ears" to hold the strips at the front. Then I clip the strips to length using nail clippers, apply the glue to the ribs using a toothpick, and add another strip of tape at the rear to prevent movement.
This panel sits on a simple wooden jig and 1/8" Super Sport rubber is wrapped over each rib location to hold the strips in place.
I add a small finishing nail at each rib location into the jig and use a single piece of rubber that wraps around each pin.

See the photos attached. This is an F1B stabilizer. The "jig" is just a suitable piece of hardwood with a plan attached with 3M 77 spray glue. I ironed a layer of Doculam onto the plan to seal it, but Saran wrap would do too. Note that this is for a flat bottom airfoil. For under cambered surfaces, you can add some "ribs" to the jig which correspond to each rib location. They can be thicker than the actual ribs.
When I slice up the strips on the glass plate, I first cover the entire surface of the carbon sheet (I use 0.003" thick uni-directional carbon fiber) with Scotch Magic Mending tape. Some of the tape extends onto the glass. When sliced, the excess tape becomes the "ears" shown in the photos which attach the carbon strips to the leading edge. I leave the tape on the top surface of the carbon strips until the glue is cured. Then the tape is pulled off. This way no glue gets onto the strips during the glue set-up. Hence I don't need to sand the strips!
By the way, this is a much faster way to do this than using thick CA. Or using tow and laminating resin. And the resulting strip/balsa bond is very light and strong and resists heat from the covering iron very well.


Tmat
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Re: Best adhesive for carbon capstrips and balsa to carbon fiber
Re: Best adhesive for carbon capstrips and balsa to carbon fiber
Re: Best adhesive for carbon capstrips and balsa to carbon fiber
Re: Best adhesive for carbon capstrips and balsa to carbon fiber
Re: Best adhesive for carbon capstrips and balsa to carbon fiber
Re: Best adhesive for carbon capstrips and balsa to carbon fiber
« Last Edit: October 10, 2020, 02:20:54 PM by Tmat » Logged

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Tmat
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« Reply #12 on: October 10, 2020, 02:25:10 PM »

Attached is a detail photo of the finished stab before covering. No sanding is required on the cap strips.
Now, a better technique is to make the ribs as a wide balsa block, laminate the carbon top and bottom, then slice the ribs out of the block using a diamond disk.
However, for one off efforts such as shown the method I described is perfectly adequate.

Tmat
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Re: Best adhesive for carbon capstrips and balsa to carbon fiber
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flydean1
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« Reply #13 on: October 10, 2020, 07:10:16 PM »

Do you attach the strips to the bottom of the ribs in a separate operation, or do you do both top and bottom together?  I think the DP 460 has a fairly long working time.  I have some that I use to attach ply radial engine mounts to the front of fuselages.
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Tmat
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« Reply #14 on: October 16, 2020, 05:45:58 PM »

FlyDean, top and bottom at the same time.

Tmat
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PantherM100
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« Reply #15 on: October 16, 2020, 06:30:48 PM »

TMAT:
I just ordered a couple cartridges of the 3M DP-460, and a gun from Perigee. 
Let me make sure I have this correct.  I squeeze out a small amount from the gun.  Mix, and apply with toothpick.
Thanks very much for the photos and how
Too!
Sincerely, 
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Tmat
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« Reply #16 on: October 16, 2020, 09:02:21 PM »

You have it right.
Mix it thoroughly, then apply with a toothpick. It cures slowly.

Tony
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flydean1
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« Reply #17 on: October 16, 2020, 10:47:34 PM »

There's a special spout that attaches to the tube and mixes the glue on the way out the end.  Unfortunately, you wind up throwing away any glue in the spout.  I never buy the spout.

I carefully squeeze out from both cartridges using the plunger gun making sure they don't touch.  Then I mix them on a piece of cardboard and apply with toothpick. 

With a clean toothpick, I thoroughly  clean each orifice before rotating the sealing cap in place.  Of course, I use a different toothpick for each hole.

I'll have to read the directions but I think you have quite a bit of working time.
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« Reply #18 on: March 24, 2021, 07:35:14 PM »

Apologies for the thread necromancy ...

I'm planning on building a light-duty flying wing using CF arrowshafts.

I take it the "appropriate adhesive" for the job is some sort of epoxy?

Beacon, Duco, and Ambroid are "out" ...?

Best-
Dave



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lincoln
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« Reply #19 on: March 25, 2021, 09:20:34 AM »

I don't know about Duco cor carbon fiber, though it seems to me a good fit would be critical.

I used some laminating epoxy to put a carbon strip on a basswood spar. It was really easy to peel off. Maybe it would have been strong enough for balsa. I recommend testing before using laminating epoxy for this. OTOH, 30 minute epoxy from the hobby store gripped tenaciously. I suppose it's possible that WEST, Raka, etc. are enough of a compromise to be suitable, but I haven't tried it. Suggest using glue for gluing and laminating epoxy for laminating.
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dosco
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« Reply #20 on: March 25, 2021, 09:55:09 AM »

OTOH, 30 minute epoxy from the hobby store gripped tenaciously.

Yeah ... I was thinking that a visit to Lowes or Home Depot would work, fetch some 5 minute or 30 minute epoxy.

Wanted to double-check.

Best-
Dave
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Tapio Linkosalo
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« Reply #21 on: March 25, 2021, 10:01:14 AM »

I used some laminating epoxy to put a carbon strip on a basswood spar. It was really easy to peel off. Maybe it would have been strong enough for balsa. I recommend testing before using laminating epoxy for this.

Which part did it peel off, basswood or carbon? Could it be that the carbon had a layer of release agent on it?

I have made my ribs for decades by carving a rib block from a chunk of balsa, laminating the caps from uni-directional balsa onto the block, and then cutting individual ribs off the block with a diamond circular saw (miniature tabletop one). When the caps pop off this is typically as the balsa rib gets crushed.
   
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« Reply #22 on: March 25, 2021, 05:59:33 PM »

The 2003 BMFA Free Flight Forum Report had a paper on slicing carbon-capped ribs from a laminated block. It was based round a bench grinder running a 1mm diamond disk. In the 2009 Report there was another paper on slicing them on a lathe fitted with a 0.75mm slitting saw. Details of all the Reports here:
https://freeflight.bmfa.org/forum-reports-contents   
and prices here:https://freeflight.bmfa.org/technical-information/48-2
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lincoln
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« Reply #23 on: March 25, 2021, 07:31:42 PM »

Tapio,
The epoxy didn't come off by itself. I don't remember whether it stayed on the carbon, the wood, or both. While I can't specifically remember doing so, I make a point of cleaning and sanding before I use glue.

dosco:
I suggest the slowest epoxy they have, though the 30 minute stuff is probably fine except on hot days. I think 5 minute epoxy MAY be adequate with carbon on balsa, but if it was me, I'd test first, and only use of on cool days. Actually, if it was me I'd use the slow stuff.
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