When I first started seakayaking, I found the tight quarters very confining. The hard fiberglass seat was tough on my back and derriere. After a few hours of paddling, I was ready to bail out. Now I always place something under my knees, and the legs last much longer. My back seems to have adjusted to the seat. I also try to move my legs and back periodically, to get a little relief. ******************************************************** Now for the other topic. We have had numerous comments concerning how long a plastic kayak will last. But my craft is fiberglass, so naturally one wonders-how long can you expect a fiberglass kayak to last? In other words, if X=lifetime, what is the mean and variance of X, and what is the family of probability distributions for X? Finally, what are the covariates of X? ******************************************************** ********************************************************************** Bradford R. Crain E-mail: brad_at_mth.pdx.edu Dept. of Mathematics Phone: (503) 725-3127 Portland State Univ. FAX: (503) 725-3661 P.O. Box 751 Portland, Or. 97207 ********************************************************************** *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
> Now for the other topic. We have had numerous comments > concerning how long a plastic kayak will last. But my craft is > fiberglass, so naturally one wonders-how long can you expect a > fiberglass kayak to last? I know of one yacht, on a mooring, 35+ years old. Your glass kayak could outlast you. Alex -- ---------------------------------------------------- Alex Ferguson a.ferguson_at_chem.canterbury.ac.nz Electronics Workshop, Chem Dept, Univ of Canterbury Christchurch, New Zealand *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
Years ago, my kevlar Whitewater II canoe gradually faded into history as a result of - something. I've always thought it was UV exposure, since the canoe was stored outside and without a cover, 3 seasons of the year. But maybe it was something else. Now whenever I think of that canoe I think of Gene Jensen. Hope things go better for him (with his recent stroke) than would be expected... - Bill Hansen *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
Hank wrote; > >I've never seen that, Bob, and I've used Kevlar in boats and paddles for >over 25 years. (SNIP) I have seen boats from four different major manufacturers that degraded to the point where the finger test failed. In defence of the manufacturers all of the boats were built during the days before Vinyl ester resins. So, the resins used were probably Isopthalics at best or orthopthalics at worst, The failure (Steve Freund can correct me on this if I am wrong) is due to the absence of UV stabilisers in the resin. In my day UV stabilisers had a purple color and people didn't like the look of them. Hank's experience not withstanding clear resins do not appear to perform as well as pigmented resins. 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/ ***************************************************************************
Subject: Re: [Paddlewise] & fiberglass John Winters wrote: (SNIP) I have seen boats from four different major manufacturers that degraded to the point where the finger test failed. In defence of the manufacturers all of the boats were built during the days before Vinyl ester resins. So, the resins used were probably Isopthalics at best or orthopthalics at worst. What does "isopthalics" mean? What does "orthopthalics" mean? They ain't in any of my dictionaries! Thanks, Dave *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
Dave Williams wrote: > > John Winters wrote: > (SNIP) > I have seen boats from four different major manufacturers that degraded to > the point where the finger test failed. In defence of the manufacturers all > of the boats were built during the days before Vinyl ester resins. So, the > resins used were probably Isophthalics at best or orthophthalics at worst. > > What does "isophthalics" mean? > > What does "orthophthalics" mean? [snip] These are different isomers of phthalic acid -- the benzene-based dicarboxylic acid which forms part of the backbone of a phthalate-ester-based polymer. Isomers are molecules having the same atomic composition but a different arrangement of the atoms. In practical terms, I suspect the phthalate ester-based polymers were more susceptible to early embrittling, and were not as tough as the vinylester-based polymers. Your dictionary may have them listed the way I have spelled them. -- Dave Kruger Astoria, OR chemist *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
>Dave Williams wrote: >> What does "isophthalics" mean? >> >> What does "orthophthalics" mean? Dave Kruger gave us the chemistry side. What it means to us mere mortal paddler types is that isophthalic polyester is stronger (and more expensive) than orthophthalic resin. I think there is more crosslinking between the molecules in iso than with ortho. Could be some other characteristics are better also, but Dave K would be the guy to quiz about that <grin>. Vinylester is even better yet (and more expensive still) and some epoxies are the best (and often *lots* more expensive. Iso is a bit newer than ortho and vinylester is newer still. Epoxy has been around for quite a while, too, but many of the newer ones are better than the old originals. Hank Hays Lightning Paddles *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
Hank Hays wrote: > > >Dave Williams wrote: > >> What does "isophthalics" mean? > >> > >> What does "orthophthalics" mean? > > [snip} ... isophthalic polyester is stronger (and more > expensive) than orthophthalic resin. I think there is more crosslinking > between the molecules in iso than with ortho. Could be some other > characteristics are better also, but Dave K would be the guy to quiz about > that <grin>. Vinylester is even better yet (and more expensive still) and > some epoxies are the best (and often *lots* more expensive. Iso is a bit > newer than ortho and vinylester is newer still. Epoxy has been around for > quite a while, too, but many of the newer ones are better than the old > originals. To round out Hank's summary, here is a little more information. Extracted from this commercial boat-building site, which also touches on other resin issues: http://www.duroplastic.com/art_bbfg.html Actually, Hank has a lot of this same information on his business's Web site, IIRC (http://www.paddles.com/index.html). --BEGIN: RESIN TYPES There is a choice of resins too, on a rising scale of cost and performance, orthophthalic polyester being the cheapest and easiest to use. (Incidentally, it is not the resin that gives a freshly moulded boat its characteristic smell, but the styrene solvent.) Next comes isophthalic polyester, 50% more expensive, but more resilient and with better resistance to water (see under "Blistering". Then there's vinylester, stronger and more water resistant still, but more than double the price of ortho-polyester. All three behave in the same way chemically, and begin to cure following the addition of a tiny amount (1-2%) of a catalyst to start the polymerisation process. And finally there's epoxy, five times the price of ortho-polyester but far superior in every other respect, notably in its resistance to water degradation as well as in its adhesive strength. Instead of a catalyst, epoxy requires a large proportion of hardener to start the reaction (from 20% to as much as 50%, depending on the particular product) and this hardener forms part of the final polymer. The use of epoxy allows composites to be produced with very high fibre-to-resin ratios making them much stronger and lighter than is possible with the other resins, but it is still too costly to be considered as a universal replacement for them. --END -- Dave Kruger Astoria, OR *************************************************************************** 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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