Christmas at the inlaws (Amie's family is crazier than mine!) led me to idle away some time with a calculator and a recent issue of Sea Kayaker. I found a web site indicating that Unca Timmy's sponsons are 40 inches long and 6 inches in diameter. Ignoring the shape at the end (i.e. assuming they are a cylinder) gives a volume of 17.7 liters each side. This provides a maximum bouyancy of 39 lb per side (fully submerged). Assuming a max beam of 22 inches, the center of bouyancy of the sponson is 11 + 3 = 14 inches from the kayak centerline, which yields a maximum righting moment of 14 * 39/12 = 45.5 ft-lb. (A paddle float, by comparison yields about 90 or so ft-lb righting moment.) There's a bit of a fudge on the geometry here, since I'm taking the moment arm for a level kayak and using the force in a fully submerged sponson (implying a heeled kayak). The Dec 2001 issue shows the stability curve for a Viking Expedition (21.75 in. beam). I look at it and compare the curves for a 150 paddler with and without 100 lb of cargo. The difference is about 40 ft-lb. Interesting. I checked other single kayaks in other issues and most show the same general trend - fully loaded without sponsons is similar to empty with sponsons. The reason I did this was because I've been curious about the fact that my experiments with the sponsons a couple of years ago found them to not be particularly tremendous at stabilizing a kayak compared to unohoo's claims. But I've had a hard time squaring my experiments with seeing a friend demonstrate standing in an empty kayak with sponsons. I've done lots of playing (i.e. rolling, self- and assisted-rescue practice and general fooling around (including paddling while standing)) in an empty kayak, but rarely with a fully loaded kayak. So: Has anyone stood up in a heavily loaded kayak? is it particularly difficult to balance? Is 100 lb cargo much of an upper limit on typical loads? (I've never weighed all my gear) It sounds high to me. Mike PS - these numbers aren't the same as redoing the Nautilus model with and without sponsons. Don't quote them to friends with any built-in assumptions. This is strictly back-of-the-envelope fooling around. *************************************************************************** PaddleWise Paddling Mailing List - Any opinions or suggestions expressed here are solely those of the writer(s). You must assume the entire responsibility for reliance upon them. All postings copyright the author. Submissions: PaddleWise_at_PaddleWise.net Subscriptions: PaddleWise-request_at_PaddleWise.net Website: http://www.paddlewise.net/ ***************************************************************************Received on Wed Dec 26 2001 - 17:36:16 PST
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