Re: [Paddlewise] Paddle flutter

At 12:56 PM -0500 11/30/01, Michael Daly wrote:
>Snip>
>Tilting the blade enough will eliminate the symmetry and reduce the problem,
>as some have suggested.  This, however, sounds like the wrong approach
>IMHO.  Good paddles don't have objectionable flutter even if drawn straight
>through the water.

There is a good explanation of the benefit of angling the blade 
slightly at: http://courses.washington.edu/phys208/notes/lect19.html

Summarizing: There will always be two matching vortices (to conserve 
angular momentum). Angling the blade causes one vortex to spin free 
while the other causes rotation of water around the blade. Since this 
second vortex around the blade effects a greater mass of water than 
if it were spinning free (as it would in an un-angled blade) it is 
more efficient. This efficiency is due to the principle that pushing 
a large mass of water slowly is more efficient than moving a small 
mass rapidly.

I think that the reason most people don't experience flutter is they 
unconsciously angle the blade slightly, either that or they keep the 
force down below the range where it creates vortex shedding, again 
unconsciously. The people I've talked to who had problems with paddle 
flutter usually report it goes away seemingly of its own accord. 
Since it is unlikely the paddle got better, it is more likely they 
adjusted their technique without knowing it.

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