At 8:55 AM -0400 5/24/99, John Winters wrote: <snip A whole bunch of stuff> > >The flow indicates where the water goes. To assume that it doesn't go where >it is going kind of boggles. > One demonstration of water diving below the boat can be seen in shallow water. Most people have probably experienced the big wake and slow progress you get when paddling in water 1 foot deep or so. The easy explanation for this is waves like deep water so the stack up like surf at a beach. But, your boat is not effected by the size of the wave once the wave leaves the boat. You don't go slower just because your wake encounters shallow water. There must be some other explanation. Water flowing under the boat must be displaced and in turn displace other water farther down and out. This chain of displacement eventually will push out to the surface. But this is pushing fairly slowly, albiet a large mass. When you get into shallow water, the water has fewer choices on where it can go so it must move faster. This is made worse by the Bernoulli effect which sucks the stern down even further making it even harder for the water to get out of the way. Even though it may be pushing less water it is pushing it out of the way at a higher velocity. The energy in the water due to the motion is KE=1/2 m v^2. Moving a large mass slowly tends to be more efficient than moving a small mass rapidly. The result is when the energy is released at the water surface, larger waves are made. If the water was being pushed purely to the side, you would not see such a dramatic change in shallow water. The typical wake of a kayak is pretty small. Probably small enough to travel pretty easily in 1 foot of water. If the water was just being pushed to the side, not much would change in shallow water, but because the water must find a fast way to get out of the way, shallow water slows you down. Nick Nick Schade Guillemot Kayaks 10 Ash Swamp Rd Glastonbury, CT 06033 (860) 659-8847 Schade_at_guillemot-kayaks.com http://www.guillemot-kayaks.com/ >>>>"It's not just Art, It's a Craft!"<<<< *************************************************************************** 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 Tue May 25 1999 - 08:04:17 PDT
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