I'm not certain that, for canoes and kayaks, there is any practical difference between gelcoat and either epoxy or polyester resin. I just completed repairing a gouge in the hull of my Dagger Meridian. I used a clear polyester resin which is very similar to the original, pigmented material in the external layer. One of these days I'll add a surface coat with the correct pigment in order to hide the patch, but in the meantime I'm going to be paddling like I usually do. Bob -------------------------------------------------- Robert C. Perkins, Ph.D. Associate Dean for Research and Planning Methodist College, Fayetteville, NC 28311 910-630-7037 rperkins_at_methodist.edu *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
Bob Wrote; - >So what's the difference between gelcote and resin especially in >regards to repairs of cracks and other minor tasks. Gel coats are usually (but not always) more flexible resins that will absorb more impact without cracking. The are usually sprayed to a thickness of 10 to 15 mils without any fiber reinforcement. The gel coat resin is modified by adding UV stabilisers (rarely used in laminating resins), thixotropic materials to keep it from running when it is applied in the mold, pigments, fillers, and other additives to obtain specific characteristics. It is a bit of a witch's brew of materials. Because of the fillers etch. gel coats are not good for laminating. They don't impregnate the fiber fully and lack adhesion. Because they lack the fillers etc.. laminating resins are not good for surface coatings. Both materials have a specific job to do and it is best to use them for the purpose they were intended. I.e. use gel coats on the surface and resins for laminating. Some boats are built by adding pigment or pigmented resins the laminating resin. This reduces weight at some loss of visual appeal as the fiber often shows through at the surface. For boats that are continuously in the water this is a bad practice as water will wick into the fibers and reduce strength an cause blistering. gel coat (and other surface treatments) help resist this permeation by water. On sea kayaks I don't feel this is a problem because the boats don't stay in the water permanently and my own boats have all been built without the gel coat layer with no problems appearing. The flip side, as mentioned earlier, is that they aren't as pretty because the color isn't uniform and the fiber pattern shows through. I would be concerned if the boats were stored outside and exposed t the sun al the time for then the small amount of pigment and fillers in the mix might not provide adequate protection and a loss of strength will occur. Some manufacturers laminate boats with clear gel coats and my conversations with rental operations is that this reduces the life of the boat. I have seen one Kevlar boat that I could push my finger straight through the laminate. While the manufacturer would not admit it I suspect the resin and gel coat used lacked UV stabilisers as I have not seen other boats that were quite that bad. *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
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