Re: [Paddlewise] [PaddleWise] Paddles

Matt wrote:

>>I still can't figure out why the paddler made almost the same distance per
stroke without also using more
energy to go faster (when using a higher stroke rate with the narrower
blade). It just doesn't compute. It takes a given amount of energy to move a
given kayak at a given speed though the water. If you move it faster that
takes more energy.


Matt,

It is simple, there was more net thrust available from one of the paddles
than the other, with presumably the same apparent effort from the paddler.
As far as reaching any general conclusions there are a couple of
complicating factors:  assuming the total power output was the same (which
is not related to the stroke rate--lower force x higher stroke rate, or
higher force x lower stroke rate could make the same power output), then
faster speed would occur with the more efficient paddle, if you had the same
power output.

OTOH, if the higher stroke rate allowed for a more efficient use of the
paddler's available energy because of better suited bio-mechanics of the
body/muscle "machine" at the higher stroke rate, than more power would
actually be available to create more thrust.  So he may have put out more
power, even though the effort felt the same.

In either case, it is likely that he paddled at the rate he felt comfortable
with each paddle at the same apparent effort level.  The results was there
was more net thrust with the higher aspect ratio blade and higher stroke
rate than there was with the other, so he could maintain a higher speed
(with the higher drag).

Of course the difficulty is that this would vary for one person to the next,
and the blade shapes and profiles are probably not the same, nor the weight
of each paddle.  And the higher speed may have favored that particular blade
shape.  It is entirely possible that a different weight, size and strength
paddler would get different results.

 So without carefully controlled tests there are no general conclusions to
be drawn here except that the higher aspect ratio paddle worked better for
him on that day in those conditions.  IF all other factors were the same, it
can be proven [both theoretically and probably experimentally] that a higher
aspect ratio blade will convert more of the available power into thrust than
will the lower aspect ratio blade.  The problem is there many other
complicating factors, the least of which is the variation in human factors
from one person to the next, which could nullify any meaningful gain with
changes in aspect ratio.

One thing for sure, more tests done under controlled conditions with
different paddlers, and paddles would be very interesting.

Peter

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