Re: [Paddlewise] Paddle flutter

At 10:26 AM -0500 11/30/01, Michael Vandamm wrote:
><snip> the
>primary cause of paddle flutter is cavitation, i.e. the formation and
>separation of bubbles at the back of the blade as it is drawn through the
>water. Lightweight, thin blades tend to be more prone to flutter than
>thicker, heavier blades. Cavitation reduces the efficiency of the paddle
>stroke, so racers try to reduce cavitation as much as possible.
<snip>

The correct term is "ventilation" not "cavitation". Ventilation is 
air brought down from the surface. Cavitation is a bubble produced by 
a blade moving with such force that a vacuum appears behind the 
blade. This happens with high speed motor boats and submarines, but 
is impossible for a kayaker to produce. Cavitation is what produces 
the pitting on outboard motor propeller blades. The collapse of the 
cavitation bubble releases a lot of energy which eventually eats into 
the propeller.

The technique of spearing the paddle into the water will help reduce 
ventilation as it reduces the amount of air from being pulled down 
during the stroke. However, this is not a cure for flutter which can 
happen with or without ventilation. And ventilation may occur with 
paddles that show no sign of flutter.

Ventilation is a bad thing in that you are moving air instead of 
water. And like paddling without touching the water, moving air is 
not as efficient as moving water.

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