Builders' Forum Archives
Re: SH 17 +carbon/kevlar
Posted by LeeG on Jan 26, 2006
I went through a few permutations of trying out kevlar, polyester, carbon, s-glass and e-glass on kayaks. What I found out is that how you apply epoxy makes the biggest difference. If you put a lot of some kind of cloth it weighs more than if you put a little. If you have a lot of some cloth then things are very strong and heavy,,but there's some spot that needs repairing anyway and it's not related to ultimate strength failures. Carbon and plywood is a weird combination. I've seen some tests that showed it resulting in a weaker panel than the same weight of glass because the wood failed at the carbon/wood boundary sooner than the wood itself would fail because the two materials are so dissimilar. It's not like making a laminate where the carbon is the dominant structural material and it can all fail together. I have used carbon over a rudder spindle hole where the end pour/wood was cracking, essentially replicating a metal rudder mount. I could see making a carbon rib with unidirectional tape then covering that with a larger piece of cloth,,,but a strip of 4mm ply tapered and covered with light cloth would work as well. I put 2" 10oz. unidirectional carbon along the keeline of a Northbay and wrapped it over the ends,,it looked neat and made for a VERY HARD surface. But used a lot of epoxy doing so. With 4oz glass over the entire hull and deck with some 1 1/2" kevlar tape on the inside keeline it looked slick,,,but really only added ridiculous strength in a 1 1/2" wide strip that is already way strong. I could have put another layer of 4oz over the entire bottom and had a more useful application of epoxy. Not to discourage you from having a good time. Make some test panels, see how the stuff breaks and use it. Running a length of the carbon and kevlar along the underside of the foredeck would be cool. You could stand on it afterwards.
In Response to: Re: SH 17 +carbon/kevlar by Bob on Jan 26, 2006