I was just reading Matt Broze's article in August's Sea Kayaker magazine about the amount of resistance generated at different speeds. Its clear that the drag resistance builds up pretty quickly going from 3.0->3.5->4.0 knots: 3.0 knots -> 2 pounds of resistance 3.5 knots -> 3 pounds of resistance 4.0 knots -> 4 pounds of resistance. So, going from 3.0->3.5 knots there is a 50% increase in resistance for only a 17% increase in speed, and from 3.5->4.0 knots a 33% increase in speed for only a 14% increase in speed. Given the significantly increased resistance going from 3.0 to 3.5 knots, and that this is in the common cruising speed range, I wonder why Sea Kayaker doesn't give resistance figures for 3.5 knots in their kayak reviews. Are kayak's resistance just too similar at this speed to make this info worthwhile? I've also noticed that when short sprint speeds are given (determined with a knotometer),they often peak out at about 6.25 knots, even though the resistance fiqures at the 5 & 6 knot range may be quite different. Any thoughts? Norman Strutin (SF Bay Area) *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
At 11:35 PM 7/5/98 -0700, you wrote: >I was just reading Matt Broze's article in August's Sea Kayaker magazine >about the amount of resistance generated at different speeds. Its clear >that the drag resistance builds up pretty quickly going from >3.0->3.5->4.0 knots: > >3.0 knots -> 2 pounds of resistance >3.5 knots -> 3 pounds of resistance >4.0 knots -> 4 pounds of resistance. > >So, going from 3.0->3.5 knots there is a 50% increase in resistance for >only a 17% increase in speed, and from 3.5->4.0 knots a 33% increase in >speed for only a 14% increase in speed. > >Given the significantly increased resistance going from 3.0 to 3.5 >knots, and that this is in the common cruising speed range, I wonder why >Sea Kayaker doesn't give resistance figures for 3.5 knots in their kayak >reviews. Are kayak's resistance just too similar at this speed to make >this info worthwhile? > >I've also noticed that when short sprint speeds are given (determined >with a knotometer),they often peak out at about 6.25 knots, even though >the resistance fiqures at the 5 & 6 knot range may be quite different. >Any thoughts? > >Norman Strutin >(SF Bay Area) The esteemed Prof. Winters understands this hull resistance best. I just know that MUSCULAR exertion at the top end of the curve gets really steep while gains in speed flatten out for all sorts of reasons. I.e. It requires much more effort to increase speed from 6 kt. to 6.25 than it does to increase from 3 kt. to 3.25. Hull resistance is part of the equation, but the cardiovasular and aerobic/anaerobic indices come into play too. If we could get the hulls to plane, that would toss a whole new set of parameters into the mix. So what *do* the stat and math people call all this??? "Poly-factorial?" "Multi-variable?" "Can of worms?" Quasi-numerically, Geo./Svenn ______________________________ George Bergeron, Secretary '99 Oswego Heritage Council www.europa.com/~heritage/ *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
Norm wrote; (SNIP) >Given the significantly increased resistance going from 3.0 to 3.5 >knots, and that this is in the common cruising speed range, I wonder why >Sea Kayaker doesn't give resistance figures for 3.5 knots in their kayak >reviews. Are kayak's resistance just too similar at this speed to make >this info worthwhile? I can't say why Sea Kayaker doesn't publish data at the lower speed range. You will have to ask them about that. Actually the differences only seem small. Relative to the power output of paddlers they are rather large. > >I've also noticed that when short sprint speeds are given (determined >with a knotometer),they often peak out at about 6.25 knots, even though >the resistance fiqures at the 5 & 6 knot range may be quite different. >Any thoughts? There is so much psychology involved in this that one should not place a lot of value to paddler testing where resistance is concerned. The paddler tests and evaluations of the boats are as much a measure of the paddlers as they are the boats. Maybe more so. 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/ ***************************************************************************
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