Re: [Paddlewise] surfing and hard chines

From: Matt Broze <mkayaks_at_oz.net>
Date: Fri, 18 Jan 2002 00:23:50 -0800
Mike wrote:

<SNIP>>>>>>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).<<<<<<SNIP>

This is from memory, but it is my understanding that the range between a
speed/length ratio of 1.5 to (something like) 2.5 (or was it 2.25) is
considered the semi-planing range and that true planing is only happening at
speeds above that. Fast ships such as Naval Destroyers operate in this
range. So a kayak with a 16 foot waterline (and a planing hull) wouldn't be
fully planing until its speed was up to 9 or 10 knots. Even Greg Barton
can't do this speed in a sea kayak (but I've seen him do almost 7.9 knots in
a 19' 8" long Seda Glider). I think it is considered to be true planing when
the bow comes back down in relation to the stern and the boat is approaching
a more level orientation again after have climbed out of its own hole in the
water against the force of gravity (?using a moving inclined plane?).

Matt Broze
http://www.marinerkayaks.com


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Received on Fri Jan 18 2002 - 00:19:33 PST

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