Re: [Paddlewise] surfing and hard chines

From: Michael Daly <michaeldaly_at_rogers.com>
Date: Thu, 17 Jan 2002 17:05:53 -0500
From: "Kevin Whilden" <kevin_at_yourplanetearth.org>

> Incidently, it is my theory that whitewater boats need wide flat hulls with
> lots of wetted surface area because of the paddler's inability to hold a
> boat perfectly flat to the wave's local surface.  This is a crutch for
> non-pro paddlers like me.  A 23" wide flat bottom rodeo boat would spin just
> as well a 26" boat if the paddler is good enough.  However a wider boat is
> probably an enhancement for balanced volume distribution during
> cartwheeling, and hence we'll never see a supper skinny rodeo boat (only
> squirt boats).

Actually, long boats need higher speeds to plane.  To plane in white water,
you'd need a short boat.  (I'm not going to partake in the debate over
planing vs surfing anymore).

Basically, to plane, you need to hit a speed/length ration of 1.5 or greater.
The speed/length ratio is the speed divided by the square root of the length.
This is familiar, as hull speed is defined as a speed/length ratio of 1.34.
So you have to go at least 12% above hull speed to plane (ICF racers in 
kayaks excede this without planing - not a planing hull).

A long, wide WW kayak will be a displacement kayak unless you get into some
really scary water velocities.  A short narrow kayak will sink :-)

Mike




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Received on Thu Jan 17 2002 - 14:27:31 PST

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