>There is no simple way to answer this accurately because as you increase >displacement various form parameters change too. Wetted surface increase, >prismatic coefficient may increase or decrease, length and beam ill >increase an so on. But if we assumed the unlikely case that everything >remained constant here is an example of what might happen. These are >resistance figures for a 13.7' waterline kayak at 215 and 430 pounds. The >speeds begin at 2 knots and increase in half knot increments up to six >knots > >For 215 pound kayak > >0.760, 1.139, 1.591, 2.252, 3.265, 4.841, 7.435, 10.525 ,13.869 > >For 430 pound kayak > >0.789, 1.184, 1.657, 2.440, 3.784, 5.569, 9.453, 13.703, 18.427 > >There isn't much difference at low speeds where wavemaking is small but >once wavemaking becomes important things happen pretty quickly. At 4.0 >knots there is about 15% difference. Keep in mind that, because I haven't >included any of the other changes this would be higher in real life. > >Cheers, >John Winters The example you cite is for a very large increase in weight. What if the weight delta were smaller and you made the assumption that the drag difference was zero? Then the inertia would be the only effect. Would it be better to have slightly more weight and be slowed less? Especially in choppy conditions. Another question. If the weight delta were smaller, would the knee of the curve of increased drag occur at a higher speed? If so the effect of increased weight might be less than expected at touring speed. Jerry *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************Received on Sat Apr 04 1998 - 07:58:08 PST
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