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Author Topic: Bonding balsa to carbon  (Read 1399 times)
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Skymon
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« on: July 18, 2017, 07:26:33 AM »

Hello, I'm after advice on adhesive.
I need to bond a balsa pillar to a carbon tube fuselage.
It's for indoor HLG, so lightweight is required.
I'm tempted with two part epoxy, but I'm concerned about the weight.
Possibly just make a great fitting joint, squeeze out well and wipe off excess..?
Best regards
Si
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Olbill
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« Reply #1 on: July 18, 2017, 09:49:26 AM »

Duco will work. Epoxy will work but is heavier.

I use a foam spacer/pylon under wings with screw attachment. Small incidence changes can be made by adjusting the screws. The foam can be glued to the carbon tube with epoxy. The foam I prefer for this is the core from Dollar Tree foam board. It can be shaped and sanded easily.

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cman
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« Reply #2 on: August 17, 2017, 04:42:11 PM »

I've used superglue without any problems.

Chris
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lincoln
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« Reply #3 on: October 26, 2017, 06:42:47 AM »

Superglue, just like a computer, lets us make mistakes faster than ever before. OTOH, I'm guessing that it sticks to composites almost as well as it sticks to fingers. (or bare feet and a hardwood floor)  ;-)

If the joint is tight, I doubt if the epoxy will weigh much. A square inch of epoxy .002 inches (.05 mm) thick only weighs .04 grams, and that's without any microballoons. Maybe it doesn't matter if it's light balsa and it's side grain, but my intuition says it might be important (and much stronger) with end grain. In that case, double gluing and an epoxy that's made as glue (rather than for use in composites) will probably lead to better results. I know I had trouble with using some epoxy I got from a boat builder to stick carbon strips onto basswood, but got much better results with hobby grade "30 minute" epoxy glue. And that wasn't even end grain.
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Olbill
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« Reply #4 on: October 26, 2017, 11:53:20 AM »

Duco will work. Epoxy will work but is heavier.

I use a foam spacer/pylon under wings with screw attachment. Small incidence changes can be made by adjusting the screws. The foam can be glued to the carbon tube with epoxy. The foam I prefer for this is the core from Dollar Tree foam board. It can be shaped and sanded easily.



A disclaimer: I probably would never use screws (or a pylon) on a Cat 1 glider. I haven't built a pure Cat 1 glider since WIF7. WIF7 only has a small balsa spacer under the wing to provide a gluing surface. It also has a balsa fuse which can be lighter than any carbon tube I've been able to get my hands on. It took a combination of a lot of tricks to achieve a 1.5g flying weight.

Duco is very light compared to any other adhesives but the other huge advantage is that if the whole glider is built with Duco then the whole glider can be disassembled when it's necessary for repairs or replacement of parts.
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lincoln
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« Reply #5 on: October 27, 2017, 06:40:41 PM »

Heat can soften epoxy glue enough to get parts off, but of course if the parts can't take the heat... I imagine tail booms are made with higher temperature epoxy so you can leave them in the form or on the mandrel or whatever for minutes or hours instead of days.

I suppose I ought to see how well Duco holds on carbon. Might be handy in some cases.
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