Re: [Paddlewise] [PaddleWise] flutter

>  1.. What causes paddle flutter in the forward stroke

flutter is an interaction between flexibility of the paddle-and-arms
combination and hydrodynamic forces.  It generally is caused by the
alternate shedding of vortexes off of opposite sides of the blade.  The
vortex will form on one edge and then wander across the back of the blade,
causing changes in pressure "pulling" the blade to one side until the angle
of incidence changes enough so a new vortex forms on the opposite edge,
which then proceeds to pull the blade in the other direction.  This will
form a "vortex street" of opposite turning vortexes in the paddles wake.

>   2.. What's the cure

A number of changes will reduce or eliminate this effect.  A different
shaped blade.  Sharper edges on the blade tend to trap and stabilize the
vortex so it does not wander over the back surface.  A few holes down the
center of the blade could also have this effect, though I know of no one who
has tried it. A stiffer shaft and firmer grip can stop or reduce it
(depending on how severe the tendency of the paddle to flutter).
    The fastest and easiest way to eliminate flutter is to change your
stroke to get some cross wise flow on the blade.  This tends to keep the
vortex shedding on the same side of the blade and keep it in one place.
There are a number of motions that will do this, the important thing to get
the some cross flow so the blade is not pulled strait back in the water.

Peter

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