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What kind of glue for a carbon fiber spar ?

Old 05-17-2015, 10:07 PM
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Eddy
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Default What kind of glue for a carbon fiber spar ?

I have almost every kind of glue on hand, including Foam - Cure for epp & epo foam, but I am looking to sandwich a 1/4" carbon fiber spar, on edge, between two sheets of white epp. Which would be the best glue to use for this application ?

Eddy
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Old 05-17-2015, 10:58 PM
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CA or epoxy. EPP can handle normal CA, but foam safe will be fine too.
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Old 05-18-2015, 07:41 AM
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Something that usually gets missed - often CF rod or tubes have a gloss surface that can resist secure bonding, a light wipe with very fine glass-paper is worth it.

I forgot to do it with the Hummer I put together .... the CF rods in the sides are now 'moving' ....

As many know I am not a CA lover and prefer epoxy. It also has a base in that when CF spars / tubes etc. are laid from 'tows' - epoxy is the preferred resin.

When I flew glow heli's back in 1980's .... many had CF tail booms. Being quite thin - they often split in tail strikes. We used tonreoair them with epoxy, clear take and heat gun.

Take split boom, smear slow set epoxy .... 1 hour variety is best ..... with heat gun play it over the epoxy to thin it and get it to soak into the splits .... wrap boom in take wound round to make the epoxy form smooth and round shape.

We could keep booms going for ages like that. Only care was to keep boom round and use a long metal tube to remove any 'hairs' inside that could damage the belt.

Just thought I'd pass it on .... !

Nigel
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Old 05-18-2015, 08:12 AM
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I would use slow-cure epoxy or Gorilla Glue. (CA tends to be too brittle for my tastes.)

And solent's absolutely correct - remember to scuff up the surface of the CF to make sure whatever glue you use has something to bite into.
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Old 05-18-2015, 12:09 PM
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solentlife
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Originally Posted by Eddy View Post
I have almost every kind of glue on hand, including Foam - Cure for epp & epo foam, but I am looking to sandwich a 1/4" carbon fiber spar, on edge, between two sheets of white epp. Which would be the best glue to use for this application ?

Eddy
In fact the difficulty is not the CF ... its the EPP ..... that is some awful foam that doesn't like many of the glues we use. Its 'rubbery' 'slippery' and glues have trouble locking onto it. Hot glue just falls away after a while ... CA needs a very good fit of joints with no air gap..... epoxy holds but can because its more stiff than EPP start to ease away with stress.

My two EPP 3D machines ... Hummer and Zlin 50 - both have an ongoing fight with this !! I used Epoxy and PU Glue (Generic Gorilla Glue).

Nigel
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Old 05-18-2015, 04:35 PM
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fhhuber
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With EPP... all glue joints are temporary.
Same with EPO.

You can peel any glue off of these materials.
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Old 05-19-2015, 04:12 AM
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Is 'Elapor' the same (or a type of) EPP? If so I've had pretty good luck with polyurethane (Gorilla) glues.
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Old 05-19-2015, 05:12 AM
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Originally Posted by FlyWheel View Post
Is 'Elapor' the same (or a type of) EPP? If so I've had pretty good luck with polyurethane (Gorilla) glues.

Not the same... but i think its related.

I haven't actually used any Elapor.
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Old 05-19-2015, 01:53 PM
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Originally Posted by FlyWheel View Post
Is 'Elapor' the same (or a type of) EPP? If so I've had pretty good luck with polyurethane (Gorilla) glues.
Elapor is what Multiplex uses and in my opinion its 'orrible !!

I have a Multiplex Twister and it must be one of the worst foamies ever ... BUT it glues up OK ... with PU Glue (Gorilla Glue) or epoxy ...

Nigel
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Old 05-20-2015, 04:38 AM
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Originally Posted by fhhuber View Post
With EPP... all glue joints are temporary.
Same with EPO.

You can peel any glue off of these materials.
Just curious, hot melt glue don't work either?
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Old 05-20-2015, 05:30 AM
  #11  
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Hot melt will hold EPP/EPO if applied well... but the poly based plastics are about the next best thing to Teflon. Stuff just doesn't really bond to it. You can peel the glue off with a bit of effort.

Even the special EPO glue will peel from EPO. I just peeled some apart to replace a damaged wing (could have repaired but I wanted the pretty new wing set) on my Dynam Me-262. I pre-sanded the surfaces (remove paint and scuff the foam for more "bite") to be glued when I put it together. Just applied force to the side of the nacelle and it came free. Then grabbed the glue and peeled it off in a sheet.
That glue would have held for hundreds more 110 mph flights...
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Old 05-20-2015, 07:37 AM
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Eddy
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Yer know, I said that the foam was epp, but that was just an assumption. It's the foam board sold by Dollar Tree ? ? ?
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Old 05-20-2015, 08:06 AM
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Originally Posted by Eddy View Post
Yer know, I said that the foam was epp, but that was just an assumption. It's the foam board sold by Dollar Tree ? ? ?
That stuff... :p not the same at all. Normal CA will eat it.

But many glues will stick permanently.

Still epoxy is one of the best choices because of the need to bond to the carbon fiber.
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Old 05-20-2015, 01:57 PM
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Epoxy forms a chemical link bond if applied to epoxy that has not completely cured. For a CF rod the resin is cured and any bond will be mechanical. I would wipe the CF with acetone to remove any wax or whatever and abrade it with sandpaper. #80 is good. For this action I use sandpaper "nail files" - I have a selection of nail files - very handy.
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Old 05-20-2015, 05:14 PM
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I have used Foam Tac and/or Beacon 3-in-1 on several foamy scratch builds and a couple of foamie kits. I have to rip the CF out of the foam if I dismantle the build. I then usually have to scrape the glue off the rod with a sharp blade to re-use it (while trying to avoid shaving into the CF).
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Old 05-20-2015, 05:35 PM
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Originally Posted by carpetbagger View Post
Epoxy forms a chemical link bond if applied to epoxy that has not completely cured.
True but only very early on in its cure ... once the catalyst catches and the reaction starts - that link is no longer available. No amount of acetone or chemical will recreate it.
Acetone in fact is a softener for cleaning up and preparing POLYESTER resin Glass Fibre repairs.
I've spent years round boatyards .. and all types of resins ... and funny thing is Epoxy is the preferred resin even when bonding to Polyester ...

[For a CF rod the resin is cured and any bond will be mechanical. I would wipe the CF with acetone to remove any wax or whatever and abrade it with sandpaper. #80 is good. For this action I use sandpaper "nail files" - I have a selection of nail files - very handy.
Not really necessary to use acetone ... any good fine sanding will do the job ...

Nigel
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Old 05-20-2015, 09:26 PM
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I use WEST and if you can dent it with your fingernail it is still active for chem bond. True about acetone, good for removing mold wax/release but the best amine blush cleanup for WEST resin is plain water = wash it down * done. Might be right about grit, but my motto is 60 grit time to quit :-)
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Old 05-20-2015, 09:37 PM
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West is Gudgeon Brothers product and most of their resins are laminating resins for laying up ....

By time epoxy has started its cure - oxidation has already occurred on surface inhibiting a true almagamating bond.

A Dunkirk motor boat I worked on years ago was adjacent to a fire .... we could pull of the layers of resin / Matt perfectly where they'd got hot and the mechanical bond had broken down. All layers were applied while previous was still fresh and long before your 'fingernail' test ....

Nigel
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Old 05-20-2015, 10:18 PM
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Obviously, Dunkirk didn't use WEST. Heat is the enemy of epoxy - about 200 deg F and the goo gets gooey and begins to give it up. Interesting - when I was sales manager at a marina we had a fire - took out seven boats, polyester resin which burned with a massive cloud of black smoke, but the glass didn't burn and wound up laying out the sides. Also of interest, the fire sort of stopped at the boat floor level - floor was sheets of plywood glassed over, wood was charred but fire died.
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Old 05-20-2015, 11:17 PM
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solentlife
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The Dunkirk Little Ship had been overlaid with West and scree mat in layers due to the general deterioration of timbers. We gave owner choice of overlaying with epoxy laminate or replacing majority of timber strakes.

The point I made was the lack of amalgamating bond shown by the layers separating after the heat. The fire was adjacent but enough distance that the boat was not physically burnt.

I am well aware of condition of boats after fires as I used to own and run a Yacht Survey Co. in UK . We had to inspect quite a number of such for insurance claims.

Nigel

Last edited by solentlife; 05-21-2015 at 08:15 AM.
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Old 05-21-2015, 03:25 AM
  #21  
kyleservicetech
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Default Hot Epoxy

Originally Posted by carpetbagger View Post
Heat is the enemy of epoxy - about 200 deg F and the goo gets gooey and begins to give it up.

For those that need to "Un-Epoxy" something, hit it with a heat gun, and peel it off with a dull knife. Same for yellow (Titebond) glue.

And, do it outdoors! The fumes are likely not a good thing to inhale.

The heat trick does not work for CA though. All CA does is stink like heck, and it still won't let go.
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