From: "Nick Schade" <schade_at_guillemot-kayaks.com> > At 5:05 PM -0500 1/17/02, Michael Daly wrote: > > > >Basically, to plane, you need to hit a speed/length ratio of 1.5 or greater. > > I think as a practical matter this is probably true. But as a thought > experiment get a short little WW kayak surfing on a wave and up there > planing along nicely. Now start building a lightweight extension on > to the bow. Light enough that it doesn't effect the trim or > displacement. At what point does the fact that the boat is longer > make it so it stops planing? If you were able to extend the bow out > 20 ft without effecting the trim, would the fact that the boat is now > 26' long and the water speed has not changed really made it so the > boat is no longer planing. Changing the hull while planing isn't necessarily the same thing as changing the hull and then trying to plane. If you changed the hull and then started moving, you'd have to exceed the hull speed of the long hull before planing begins. Once planing, the surface area in contact with water will reduce. The length that matters is the length at the start. > I think a definition based on speed/length ratio does not really > capture what we understand planing to really be. I think a definition > that incorporates the actual actions of the boat is more meaningful > than the one that specifies the power source or length vs speed. Referring to the speed/length relationship assumes that we already have figured out what a planing hull shape is all about etc. I was just trying to address Kevin's hypothesis about why planing or surfing WW kayaks are short. The length of the hull limits what they can do. The speed/length relationship demonstrates that a short kayak will plane over a wider range of water speeds (hence on more rivers) than a long one and will plane more easily. This is a marketing feature. Mike *************************************************************************** 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 Fri Jan 18 2002 - 10:03:43 PST
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