: Has any body made a kevlar kayak using their beautiful wood strip kayak as
: mold. Or is that just stupid because i could really screw up my strip
: kayak if the mold release did not work right?

This works, but usually the original wood strip mold is made particularly as a mold. Language alert: In this case you are using a "male" mold, which is commonly called a "plug". A "mold" for making cast plastic boats--including those with fancy reinforcements like carbon fiber--is a female mold.

If you take a rectangle of plywood and cut your building forms out of the center of this, then what is left would serve as a building form for a female mold, and you could strip this using conventional techniques to make a mold.

If you lay up your carbon on the outside of your existing hull you have two main problems: The resulting hull will be slightly bigger, and the outer surface will need a good deal of work (sanding) to get it smooth. Both of these situations add to drag. So, in theory, your existing wood boat would be faster to paddle than anything molded from it.

Some people make the boat, try it out, and if they like it, then they clean it up and polish it and wax it, and they use it as a plug. From this they do not make another boat directly, however. they cover the plug to make a fiberglass mold. This is typicaly made from a thick coating of sprayed-on fiberglass. The mold is removed from the plug, reinforced with more glass and resin so it is strong. Then it's cavity is polished and waxed and a boat is molded in it.

If you are working with woven cloth rather than chopped fibers you might look at using some vacuum technique to get your cloth and resin to follow the shape of the hull, whether from a plug or a mold.

Working with a mold gives yo a smoother outside, and the hull of the cast boat is the same shape and size as the hull of the original model.

I've tried using plaster of paris to make molds for fiberglassing, and it can be done. A mold for a kayak made from plaster would be very heavy, and the cost would be only slightly less than the cost of making it from fiberglass--if you have the equipment to spray on chopped glass. It would be a considerable savings over using woven glass fabric and glass mat, though. The weight of the mold is something you can't get around, though. For about the same weight, but less cost, you could use premixed concrete. it would be a bit mroe mork to seal the intereior and smooth it, but the cost would be very low and the working time would be convenient. Disposing of the mold is going to be a problem. You might decide to work outside and eventually turn it into a birdbath, or a fishpond.

Other options include inexpensive, lightweight MOLDS made from the boat hull. These molds might be made of expanding foam, papermache, or a concrete mix made from portland cement and beads of expanded styrene. Once the impression of the hull was captured in these molds you would have to do some work to seal the surface and smooth it before molding a boat in it, but a couple coats of epoxy resin would be a good start, and might be all you would need.

You don't need to use expensive epoxy resin for these projects. They can be created just as easily with less expensive polyester resin.

Consider making your molds in 3 or 4 parts. The mold for the deck can be 1 or 2 pieces-- or you can dispense with a mold and just build a deck directly on top of your hull: set in temporary frames, stretch some glass fabric over them and cover with resin. Build up thicker layers of resin and cloth to whatever thickness you wish, then remove the temporary frames. If you wish, you can lay wood strips over the frames and cover these with glass cloth and resin just as you would make a stripped deck over a plywood hull in a hybrid S&G kayak.

The mold for the hull, if made in two interlocking parts is held together with clamps until the materials for the hull have hardened. The clamps are then removed and the mold can be removed a bit more easily. You can insert wedges between the mold halves to spread them apart if necessary.

Just some general ideas. There are lots of fabrication techniques with fiberglass which are used commercially and in making one-off objects. A day of researching these on the internet will give you a good list of books to order through your local library. If they don't have them, ask about getting them through interlibrary loan.

Hope this helps

PGJ