[Paddlewise] Flutter

Always interesting to read the comments on such things as flutter.

Some might find this interesting.

Some years back while tank testing paddles I tried a number of techniques
for reducing or eliminatiung flutter. The one that worked best involved
glueing a 1" wide band of driveway de-icing salt along the perimeter of the
power face of the blade. For some reason nothing else I tried worked as
well. The paddle had an interesting "soft" feel to most paddlers that some
did not like. It also looked strange. Harry Roberts (editor of Canoesport
Journal) called it the "Gravel Paddle"

A few years later some fellows at the Air Force Academy tank tested a paddle
with a series of holes around the perimeter. This also worked and, depending
on the hole size, did not seem to reduce drag. They did not test the blade
at an angle of attack.

Many years ago during my sailboat racing days many stock boats experienced
rudder and centerboard vibration (or flutter if you prefer). Some boats
actually hummed a tune depending on the speed. The cure most often used was
to file off the trailing edge on an angle. I seem to recall it was 80
degrees but would not swear to it.

At the time I was testing paddles it occurred to me that the observed degree
and existance of flutter varied between paddlers using the same paddle. Some
casual testing suggested that the smaller the shaft diameter relative to the
paddler's hand the greater the perceived flutter. An ergonomics engineer
explained that there exists an optimal shaft size for every hand size and
that the smaller shafts probably reduced the effective grip force. The ideal
shaft size appears to be that which fits the hand in its natural repose. I
have read this same comment (the optimal size) in several ergonomics texts.

I also did some experimentation based on the observation that flutter seemed
to increase as the shaft rigidity decreased in the region of the shaft/blade
junction. I started with a paddle that had a narrow and "whippy" shaft at
the blade top. It fluttered enormously. I then began adding carbon fiber
reinforcement until, eventually, the perceived flutter disappeared.

These experiments may explain why two paddles behave differently even if
they look very much alike. A "soft" or less rigid shaft may increase the
flutter by reducing the damping effect of the shaft. Similarly the "to
small" shaft may increase the sensation similarly  by reducing the damping
effectiveness of the hands.

I suppose it might pay to examine such simple things as paddle rigidity and
shaft size if you experience flutter. You could spend a lot of time tinering
with your stroke only to discover the problem in the paddle.

Cheers,

John Winters



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