A perfect 10. 10 G. i've read that the acceleration of water in breaking ocean waves reaches a maximum of about 10 G. Continued slamming of ocean going boats can cause fatigue problems... perhaps failure. so i wonder, what design forces are used for developing kayaks? is there any real consideration beyound folks tossing them off of roof tops to see if they survive... bye bye bliven PS. i think that Prof. Longuet-Higgens of the UK computed the 10 G value back in the early '80s. *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
Larry Bliven wrote: > i've read that the acceleration of water in breaking ocean waves reaches a > maximum of about 10 G. Continued slamming of ocean going boats can cause > fatigue problems... perhaps failure. > > so i wonder, what design forces are used for developing kayaks? is there any > real consideration beyound folks tossing them off of roof tops to see if > they survive... Don't know the design forces, but suspect many manufacturers use the by guess and by golly method. Example: Eddyline's cockpit area design is a weak one. Every Eddyline boat I have owned has required some sort of repair of the coaming-deck seam. Admittedly, one of those boats was oil-canned in large surf (>6 feet?), which separated the hull-deck seam tape on each side, and popped the coaming-deck seam. The others failed in normal use, from over-leveraging my fat bod out of the cockpit. I do not believe any of them would survive anything but small surf (<4 ft) if crunched sideways by a dumping wave. OTOH, I have tried to break the deck/hull/coaming area on my Pygmy Osprey Std in small surf, and it is rock solid. It is marine ply (4 mm), with epoxy/glass inside and out. Let's hear it for the structural rigidity of wood, and the strength of epoxy/glass! -- Dave Kruger Astoria, OR cockpit breaker *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
> Larry Bliven wrote: > > > i've read that the acceleration of water in breaking ocean waves reaches a > > maximum of about 10 G. Continued slamming of ocean going boats can cause > > fatigue problems... perhaps failure. > > > > so i wonder, what design forces are used for developing kayaks? is there any > > real consideration beyound folks tossing them off of roof tops to see if > > they survive... I hope I am not starting a holy war but I doubt that any hardshell manufacturer would want to drop a nice fiberglass kayak off of a factory roof. The gelcoat would break off in pieces and scatter like the contents of a large spilled package of Chiclets. Artistic patterns of stress fractures would radiate across the hull, et al. I once was helping a friend empty water from his kevlar kayak by turning it upside down and lifting alternate ends. As we were turning it back upright, my hand slipped on the slick surface and I dropped it from just knee level. That's where I got the Chiclets imagery re the gelcoat. On the other hand I have dropped one of my folding kayaks from the moderately high roof of my mini-van. No damage aside from a slight buffed mark on the hull where it hit the concrete surface of the parking lot. The wooden frame was just fine. One or two of the longerons (thin long pieces running the length of the boat) popped out of their holders on the crossribs and just had to be pushed back into place. BTW, Nautiraid I know does drop its boats from the factory roof to see what happens. Nothing. I think the same would be true of any skin boat. There is a lot to be said about wood and wooden frames made up of parts that flex and give to absorb impact. Same with soft yielding skins instead of rigid surfaces. Aluminum tubing frame parts also have lots of resilency and will flex enough to absorb punishment. Someone related a true story that I wrote up in my newsletter of several of his folding boats being picked up by a twister and dashed against some concrete posts. Again just some scrapes on the skin from the rubbing on the rough surface. Can things break on one. Of course. But you have fairly easy repair or you can always replace the individual piece. ralph diaz -- ----------------------------------------------------------------------- Ralph Diaz . . . Folding Kayaker newsletter PO Box 0754, New York, NY 10024 Tel: 212-724-5069; E-mail: rdiaz_at_ix.netcom.com "Where's your sea kayak?"----"It's in the bag." ----------------------------------------------------------------------- *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
>What was the deal of the century? A Kevlar Romany Explorer with shortened bulkhead (lower cockpit volume) Henderson Foot pump and compass for $2200. Only one small stress fracture. The only disadvantage is that the foot pump is a little awkward to get to, but do-able. Robert *************************************************************************** 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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