John Myers wrote: > NDK and Valley Canoe do not seem to > use the vacuum bagging techniques that are common practice in North America. This I can't understand. Are vacuum bagging techniques significantly more expensive? The advantages, to me, outweigh any disadvantages I know of. > Also,the decks of the Brit boats seem to be laid up with a heavy fiberglas > matte which must take a lot of resin to wet out. This certainly does make > for a stiff deck but the added weight factor must be significant. I wonder > if rigidity equates with strength in a boat as small as a sea kayak that > travels at such minimal speeds? I learned about boat design from a naval architect friend who taught me to sail back in the '70s. He left me with the impression that glass mat construction is for the cheapest boats and "real designers" use woven glass cloth. I just double checked Walbridge's Boatbuilder's Manual and he says that mat's good for bathtubs but not recommended for boats. One advantage of mat is that the resulting material is closer to isotropic - that is, the material properties are the same in all directions. Woven cloth is stiff and strong in two directions (along the length of the threads) but less so at angles to the thread. I've heard of folks laying multiple layers of woven glass cloth at angles to each other to reduce this problem, but my guess is that is not significant in kayaks. John, Matt or others may have more insight. > Are British boats stronger or are they just resin-heavy? If anyone wants to volunteer their boats, I can supervise the testing. I've broken more than a few big steel beams in university research. Fiberglass and kevlar should be easy! > Has anyone out there experienced hull failure > in a fiberglass or composite boat that could be attributed to an overly > light layup? What boat and under what conditions did it fail? It's not easy to compare realistically the strengths of kayaks that have failed under different conditions. Anecdotal evidence tells us less than an instrumented kayak. Also, there are other details besides the shell construction. The bulkheads, coamings, hatches and other details contribute to the overall strength and stiffness, so you'd have to compare different versions of the same boat. Make a Romany Explorer using the best vacuum bagging techniques and good woven cloth then compare it to a Brit built battleship version. That'd tell us. Mike PS - Anyone care to corner Nigel Dennis or other British designer/builders at a symposium and put the question to them? *************************************************************************** PaddleWise Paddling Mailing List - All postings copyright the author and not to be reproduced outside PaddleWise without author's permission Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.paddlewise.net/ ***************************************************************************Received on Wed Jan 05 2000 - 11:22:21 PST
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