Re: [Paddlewise] Why does rocker and carving work?

At 3:03 PM -0800 12/2/01, Scot Hume wrote:
>I'm trying to understand why rocker makes a boat turn
>easier.  My current idea is that if a boat drafts 6
>inches all the way along, a sweep stroke or other
>force such as a wave has 6 inches to work against at
>the end of the boat.  However, if there is rocker, the
>power of the sweep stroke is pushing against only a
>couple of inches and it takes less force to move the
>bow on a pivot point back near the paddler.  Is this
>correct?
>
>Also, when a kayak is leaned with the right knee, does
>the boat turn because the water on the right side has
>a longer path and thus the left side is able to move
>quicker through the water so that the boat ends up
>turning to the right?
>

Anything sticking into the water is going to resist moving through 
it. When you try to turn the boat you need to overcome the resistance 
of the water to allow you to turn. Because the ends are farther away 
from the center of rotation they create a larger moment arm to create 
more resistance. Rocker reduces the area at the ends of the boat, 
thus decreasing the resistance.

Leaning the boat can have many different effects depending on the 
design of the boat, but one effect is almost universal regardless of 
the kayak. Because kayaks get narrow towards the ends, when you lean 
the boat you give it more rocker and more rocker makes it easier to 
turn (see above).

Nick
-- 
Nick Schade
Guillemot Kayaks
824 Thompson St
Glastonbury, CT 06033
(860) 659-8847
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