Re: [Paddlewise] Paddle efficiency

At 9:45 PM -0400 5/17/01, Michael Edelman wrote:
>We're almost all in agreement. Just a few more details ;-)
>
>John says:
>
>>  Nick says: > > As long as you move the paddle parallel to the 
>>direction of motion
>>  > > desired all the force applied will go directly to propelling the
>>  > > boat.
>>
>>  Nick is right although I doubt if anyone actually accomplishes this
>>  regularly. I suspect Nick mentioned this elsewhere as I recall him
>>  discussing it some time back.
>>
>
>There's still an error here. You can't assume all force applied goes
>into forward movement of the boat. No paddle or propellor is 100%
>efficient at turning effort into forward motion, and indeed,  John in
>the following paragraph quotes a study stating that racing paddles are
>87% efficient which contradicts the prior claim.
>

There is a difference between the force applied and the amount of 
energy required to generate that force. Effort and force aren't 
really the same thing. Any propulsion force will create an 
acceleration in the direction of the force. (F=ma). 100% of the force 
is used to accelerating the mass. However, you may end up applying 
more energy into creating the force than you receive out of it. So 
even though the force applied to the paddle exactly equals the force 
applied to the boat, you can not say that the energy applied to the 
paddle is equal to the energy received by the boat. Instead the 
Energy received by the boat is equal to the energy applied to the 
paddle minus the energy received by the water. Efficiency is (Energy 
to Kayak)/(Energy to Paddle) and not (Force to Kayak/Force to Paddle).

This is why when someone says: "I can push my favorite paddle just as 
hard or harder than any other paddle." you can not assume that the 
favored paddle is more efficient. And why subjective evaluations of 
paddles can be inaccurate. The amount of force you feel is not 
directly related to efficiency.
-- 
Nick Schade
Guillemot Kayaks
824 Thompson St
Glastonbury, CT 06033
(860) 659-8847
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