Don wrote; >This is a response to the kevlar thread. >I have found that Kevlar is a few ponds lighter than >fiberglass but that it does not have the rigidity of >fiberglass. Quite true. Many builders using Kevlar use cores to stiffen the panels. Cores also have problems and ductile syntactic foam cores seem to perform best where impacts might be expected while some of the sheet foams and honeycombs provide the greatest weight savings. I have an 18 pound 17' kayak that has stood up just fine for the past three years but I sure don't hit anything with it. :-) >If you want a boat made of an exotic fiber >like Kevlar I recommend that you buy a carbon and Kevlar >kayak. The carbon fibers will run one direction and the >Kevlar fibers will run in the opposite direction. That >way you will have the rigidity and lightness of carbon >in the same sheet as the flexible Kevlar fibers. True also. One word of caution. Ideally the builder will sandwich the carbon between layers of Kevlar to offset the brittle nature of carbon in thin laminates. As Hank Hays says, "Carbon is not all it is cracked up to be." (Did I get that right Hank?) I recommend that the Kevlar laminates be BI-axial and that the carbon be Uni. directional and run diagonally across the hull. This provides a good blend of stiffness and impact resistance. I have seen recent reports condemning the fabrics with mixed fiber (carbon/Kevlar and glass/carbon). Apparently stresses build up causing breakage along the carbon strands. I do not know why this occurs but have seen examples so my conservative nature leans towards avoiding these materials. Cheers, John Winters Redwing Designs Specialists in Human Powered Watercraft http://home.ican.net/~735769/ *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************Received on Sun Mar 14 1999 - 16:28:19 PST
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