Re: [Paddlewise] [PaddleWise] Clarification?

From: Peter Chopelas <pac_at_premier1.net>
Date: Tue, 14 Sep 2004 20:40:14 -0700
 John Winters wrote:

>I suspect that a lot of the confusion comes from assuming the objective is
high lift as opposed to high thrust per unit area.  If we change the
question from How do we generate more lift? to How do we generate more
thrust we may get another answer.

Why are you assuming that the important objective is high thrust per unit
area?  I think there is another element that is more important perhaps than
thrust per unit area.  I can not see how thrust per unit area is even
relevant to what is important to a paddler.  I would think that for long
distance paddling what you want to measure and optimize is thrust output per
power input (the power input is the work rate of the paddler's muscles),
this would yield the maximum distance for a given available energy.  For a
racer you would want to measure and maximize thrust output per force input
(at the shaft), this would yield the maximum speed for a given paddler's
strength.  The maximum thrust that can be generated from a given blade size
is not necessarily the most efficient paddle, efficiency has to be measured
as energy in vs. energy out, or more accurately thrust output vs. work
input.

An aircraft analogy is Short Take-off and Landing airplanes (STOL).  The
wings are shaped to generate high lift per unit area, at the expense of a
very draggy wing design in normal cruise (higher speed) mode.  The highest
lift per unit area on a wing yields a very slow and inefficient aircraft.
The most efficient aircraft do not have high lift wings, but rather high L/D
(or lift to drag ratio) wings.

Although the area of the blade may be indirectly related to these things,
ISTM that if you do not establish the correct measurements you will end up
with meaningless results.

Peter
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Received on Tue Sep 14 2004 - 20:48:24 PDT

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