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Non permanent adhesive for carbon fiber prototyping?

Old 01-07-2021, 04:23 PM
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LotsaSkink
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Question Non permanent adhesive for carbon fiber prototyping?

As part of my graduation project I'm prototyping a powered sailplane and I need some advise. The basic idea of its structure is to combine 3D printed ribs, etc. with carbon fiber pipes as spars. However, carbon fiber is expensive and if anything needs to repaired or replaced I want to be able to remove or replace anything attached to the carbon fiber.

I was originally thinking hot glue, but people are saying it could damage the epoxy. The other option would be something dissolvable like CA, dissolving it in acetone, but I'd image that would damage the epoxy as well. Anything would be very much appreciated!
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Old 01-07-2021, 08:42 PM
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quorneng
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Designing a permanent glued structure that can be readily repaired is going to be about finding a suitable compromise.
My suggestion based on my experience using printed ribs is to built some test piece wings and see how easy they are to repair for the sort of damage you anticipate.
There are just too many factors at play to give a positive answer. I would worry more about the ability of my design to undertake the required function and only worry about repairs if and when they occur.

Last edited by quorneng; 01-07-2021 at 10:38 PM.
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Old 01-08-2021, 12:38 AM
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LotsaSkink
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Originally Posted by quorneng View Post
Designing a permanent glued structure that can be readily repaired is going to be about finding a suitable compromise.
My suggestion based on my experience using printed ribs is to built some test piece wings and see how easy they are to repair for the sort of damage you anticipate.
There are just too many factors at play to give a positive answer. I would worry more about the ability of my design to undertake the required function and only worry about repairs if and when they occur.
Yeah it's probably just my fear of permanence giving me anxiety to follow through. However, repairs aside, I'll do need to have the design right.
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Old 01-08-2021, 12:36 PM
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quorneng
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That looks a reasonable design although it will depend on how it is covered.
A conventional taught film covering creates a considerable inward 'pull' on the leading and trailing edges. If that tension is not uniform, and it rarely is, it can cause the wing to warp unless it has sufficient torsional rigidity.
Remember a twist of just a one degree can have a significant impact on a wing's aerodynamic characteristics. Even a carbon tube has some degree of flex.
As the leading and trailing edges are furthest from the spar they have the biggest impact on resisting any warp so may have to be able resist loads over and above the simple pull of a film covering.
If you look at a conventional all balsa single spar wing it is likely to have quite substantial leading and trailing edges with a balsa content equal too or even more than the spar itself.
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Of course the final design does depend on what the wing is going to be used on.
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Old 01-08-2021, 03:13 PM
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LotsaSkink
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I'll probably print everything and get the "feel" of it, see where reinforcements are in order.

The idea (right now) is to have a two channel all moving v-tail. That is perhaps a dumb idea, but the more I think about it the more I can't help but to want to make it real. I'm not really into the idea of just having compliant PE-tape hinges, a conventional tail all moving tail would be to heavy as I want to make it, but a v-tail needs the just the sort of mechanical rigidity I have experience with.

This is my first time at a forum like this. If anyone wants to see the finished product then I'll be sure to post it when it's done (<1month).
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Old 01-08-2021, 04:02 PM
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quorneng
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An all moving V tail sounds quite ambitious.
I used a V tail on my sub 250 g all printed powered glider but not all moving in fact not even rudder just elevator.
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Just be aware a V tail when used as a rudder has secondary aerodynamic effects that are not so obvious in a conventional single vertical rudder arrangement which is part of the reason it is not often used in full size.
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