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Hi, Ben,
> Here are my questions: 1) how strong is strong enough?. Is the polyester
> strong enough for kayaks.
> 2) Are there any data that show that polyester is not suitable for Kayaks.
> I read a few books on boat building and all that I found on polyester are
> general statements whith no backup data. Has anyone tried it?
I don't know if there is any data but this I think doesn't need data to show. The experience of other boat builders is the best info. Most wood/polyester boats or other projects delaminate within a short period of time. Polyesters don't adhere to wood well. The oils in the wood cause this. The oilier the wood the more of a problem. Polyester was used for years as it was the best thing around but with the developement of epoxy it became less desirable.
> 3) WhenI was mixing the resin with the hardner, it turned dark. Why is
> that? (The temperature in the room was 40F).
Polyester darkens as it cures. The ideal is for it to turn a light green. If you use too much hardener it will turn brown and more still and it will turn black. This will result in a weak mixture.
You are right, polyester isn't nearly as strong as epoxy. Epoxy is consideered to be a structural adhesive and is several times stronger. The stronger the bond between the fibres the stronger the laminate. Basically, anyway.
So, yes polyester could be used on a kayak. It won't be as strong as epoxy and it won't last as long, but it will work.
Ian
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Guillemot Kayak - High
Performance Wooden Sea Kayak Designs
