Re: [Paddlewise] surfing and hard chines

From: Nick Schade <schade_at_guillemot-kayaks.com>
Date: Fri, 18 Jan 2002 10:48:13 -0500
At 10:13 PM -0500 1/17/02, Rcgibbert_at_aol.com wrote:
>In a message dated 1/17/2002 11:48:42 AM Pacific Standard Time,
>kevin_at_yourplanetearth.org writes:
>
>
>>  Yep, the knock against my Arctic Tern is that it is a little slower than a
>>  round-hull boat due to the extra wetted surface area of the crisp hard
>>  chine.  I'll take a 5% reduction in cruising speed any day for maximizing
>  > rough water and surfing performance!

As a practical matter chines don't end up adding all that much wetted 
surface because they also tend to add volume which makes the boat 
float higher which reduces the wetted surface, so it very nearly 
comes out as a wash. The worst possible difference (a perfectly 
rectangular hull section vs a perfectly semi-circular section) for 
two boats of the same width and displacement is the rectangular hull 
has 13% more wetted surface area (if I did my math right). This is 
significant, but in practical terms, neither the rounded chined or 
hard chined are anything like "perfect". Much more important to how 
much wetted area there is is the width of the waterline and the 
overall shape of the bottom (round, flat, deep "V"). The chines have 
a somewhat secondary effect.

>  >
>I agree. When travelling confused waters (eg surf, clapotis, standing waves)
>I find the hard(er) chines of a Khatsalano a better ride than the round
>chines of my Nordkapp.
>The Nordkapp, to me, is faster, but on a week long cruise...I'm just not in
>all that big a hurry.

Why are you attributing the performance difference to the chine 
shape. Are the Khatsalano and NordKapp exactly the same except for 
chine shape? Isn't the Khatsalano a folding boat and the Nordkapp 
fiberglass? Don't they have different lengths and widths. Aren't they 
actually completely different boats other than being vaguely 
"Greenland Style". Why is it the chine shape making the difference 
and not some other aspect of the design? Isn't that like tasting an 
apple and an onion and saying the apple tastes better because its red.

It would be just as wrong to assume the chine shape has nothing to do 
with the performance. Performance is dependant on hull shape and the 
chine is part of the hull and thus must have some effect on the 
performance. But, there is so much more to the hull than just the 
chine. Why insist that one aspect trumps everything else?

Nick
-- 
Nick Schade
Guillemot Kayaks
824 Thompson St
Glastonbury, CT 06033
(860) 659-8847
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Received on Fri Jan 18 2002 - 07:48:26 PST

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