I was with a friend of mine, an avid kayaker who has either built or extensively modified every piece of gear he uses, trimming weight in every place he can to be able to bring everything he needs for two weeks in the wilderness as checked luggage. And, like everyone who has a collapsible kayak, he wishes it were made out of carbon fiber.
I thought carbon fiber required a vacuum oven. But a search for “carbon fiber” AND “homebrew” brought up this guy who built a carbon fiber draft beer dispenser. And he just baked it for an hour at 250 degrees in an ordinary home oven!
Huh?
If we had “pre-preg” carbon fiber sheets, metal forms and an oven we could start making carbon fiber kayak parts?
Yes, if you ran down the equipment and supplies, you could “do” it.
However, there is a bit more to carbon structures than cut and bake - methinks you would be well advised to learn HOW to use carbon - lay-up direction, weights, etc. before screwing with stuff (such as kayaks) which really have to work under stress.
Go to Aircraft Spuce & Specialtyand look under books for composite construction. ‘How to Build Composite Aircraft’ has a lot of good information. They also carry the supplies. There are probably more recent books with more details and books specifically for kayaks and other watercraft. Kevlar makes more sense than carbon for a kayak skin because it is flexible. Carbon has great strength, but it is ‘brittle’, but it might be useful for reinforcement or stiffening. Kevlar used to cost less, I don’t know about the current market. Many first timers have successfully used composite construction in aircraft. I don’t know anything about kayak construction, but you could probably use a vacuum bag if simple wet layup and sanding is insufficient. I do recall a canoe or kayak manufacturer who was using prepreg material (fabric impregnated with adhesive) that could be cured with ultra-violet light. They found the process very simple and economical.
We’re not talking about using carbon fiber for the skin, but to replace the aluminum parts of the frame.
This is a man so obsessed with shaving off every ounce from his kit that he’d make a carbon fiber toothbrush handle.
Is simply baking the pre-preg carbon fiber acceptable? Is a vacuum not necessary? In the link in the OP, the part was just wrapped in heat shrink tape.
Is this possible?
Make a frame-work out of copper pipe. Wrap with Teflon tape. Wrap that with pre-preg carbon fiber. Wrap that with heat-shrink tape. Bake at 250 degrees. Remove from oven, let cool and pull off heat-shrink tape. Use ferric chloride solution to dissolve copper frame-work.
Homebuilt composite aircraft are not always “just” composite skin, but composite other parts as well. (One of the aircraft I’ve flown had a composite main spar, which really should be the strongest part of the airplane) I second the suggestion to get some books on composite construction, either aviation or, if you can find it, marine as well (I do know the marine stuff is out there, I’ve seen some, just can’t recall the name because it’s not a big interest of mine like aviation is).
There are a LOT of different products and techniques out there. I think your friend can do what he wants to do, but he needs to do some serious research and experiment a little with materials and techniques in order to get it done right.
Baking and/or vaccum may be unnecessary. It depends on the type of glue. Vacuum bagging is cheap and easy. And you don’t want bake anything on a metal frame. The difference in thermal expansion between the materials will be a real problem. You don’t need the teflon tape. Use aluminum instead of copper, and just use swimming pool bleach to dissolve the aluminum. Better yet, make a styrofoam shape and wrap that. Acetone will dissolve the styrofoam, but you may need it in there. Carbon has high tensile strength, but for that to work at an angle from the fiber orientation you need something to transfer forces. Get the books. Everything is explained. You won’t save any weight if you don;t use proper construction techniques.
Also, there are plenty of preformed CF tubes, angles, etc. out there. Google it.
We’re talking kayaks here - strength is not quite as important as in aircraft, but having a kayak break up because somebody thought there was something magical about carbon (or kevlar, or e-glass) is going to ruin somebody’s day.
FIND OUT what does which BEFORE spending a ton of money acquiring exactly the wrong stuff and putting it in the wrong place
As mentioned, carbon is VERY brittle - it has wonderful tenstile strength, but shatters if loaded in shear. I know - I had an 8 year old snap a carbon strand by flicking her finger.
I’ve done a LOT of kevlar and glass, including structural work.
Study. Practice. Test the results. Study why and where your results were satisfactory and why and where they were not. Understainding why something worked is every bit as important as studying the mistakes. Study how NOT to make the mistakes you did the first time (there WILL be mistakes).
Repeat repeatedly.
Look even harder for mistakes as your skill advances - the chance to make really dangerous mistakes increases as you skill does - The mistakes of an experinced glass-layer tend to hide deep, and not show under cursory examination. Instead, they show up just when you need a piece to NOT fail - A bad time to learn about hidden delamination, failure to cure, resin pockets, or other mistakes.
I knew I’d think of it eventually. Go to the West Systemssite to get info about composite construction for watercraft. I still recommend the aircraft oriented books, especially the one cited previously. That has the information you need to engineer a solution. If you don’t do it right, it will break, or end up being heavier than what you are replacing, or both.Google ‘fail’ for examples.