I'd like to add one more wrinkle to the hatch deterioration issue. A few years ago, I was involved in determining the cause of failure of a structure we made out of a combination of Kevlar and Mylar. I was introduced to a failure mode known as "stress rupture". Essentially this occurs when you load a component near but not at its strength limit for some time. Let me illustrate with some MADE-UP NUMBERS. For a particular material, if you stress it to 100% of its strength, it will fail immediately. If you load it to 95% of its strength, it will fail in 3 months. If you load it to 80% of its strength, it will fail in one year. 60%, 5 years. 50%, never. The bottom line here is that some materials (mostly organic, I think) will fail at some stress level over time that is less than their rated strength. It seems to me that VCP hatch covers are being continually stressed while on since they are stretched over their mating part. Is it possible that VCP hatch covers then can experience earlier failures when then are continually left stressed (stretched)? Of course, if this effect contributes to the hatch cover failure, it would be in addition to the previously mentioned effects of UV radiation, ozone and/or other chemicals. My 2 cents.... Bill Leonhardt *************************************************************************** PaddleWise Paddling Mailing List - All postings copyright the author and not to be reproduced/forwarded outside PaddleWise without author's permission Submissions: PaddleWise_at_PaddleWise.net Subscriptions: PaddleWise-request_at_PaddleWise.net Website: http://www.paddlewise.net/ ***************************************************************************Received on Mon Jul 31 2000 - 12:10:43 PDT
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