Re: [Paddlewise] wing theory

On Monday, June 9, 2003, at 12:09  PM, Dave Kruger wrote:

> Nick Schade <nick_at_guillemot-kayaks.com> wrote:
>
>>> Work is defined as a change in energy. If you measure the work done 
>>> by
> your hand and you have all the parameters of your paddle matched such
> that they multiply together right it is absolutely possible to make the
> work done by your hand match with substantially different paddles. But
> remember that the work done by your hand is not the same thing as the
> work done on your boat. >>
>
> Nick, a small correction:  Classically, work is defined as the force 
> applied
> multiplied by the distance through which the force is applied ( W = f 
> x d),
> not a change in energy.  The change in energy in the paddler arm/back 
> system
> is not all directed at accomplishing work.  Some goes into generating
> turbulence in the water ("vortices") which ultimately ends up heating 
> up the
> water a bit.  (The water at the bottom of Niagara Falls is warmer by a 
> tiny
> fraction of a degree because of the "stirring" achieved by the fall and
> subsequent random mixing of the water.)

W=F x D is just one form for determining the work. In the most 
generalized form this can be expressed as Work = [delta] Energy. I've 
double checked this in my physics book.

All the change of energy of the paddler arm/back system does perform 
work, it is just that some of it doesn't do anything we really find 
useful. Work is done even when all you produce is heat.

>
> Consequently, if one is interested in determining efficiency in the
> paddler/boat/water system, he/she has to be careful to delineate what 
> is
> doing work on what.  The paddler does work on the paddle (pushing it
> rearward).  The paddle does work on the water (pushing it rearward).  
> And, in
> turn, the paddler's body does work on the boat, pushing it forward.  
> How much
> work gets done on the boat, from all the thrashing of the paddle, is 
> the key.

I agree. Often the problem when trying to analyze paddling efficiency 
people is choosing an appropriate frame of reference.

>
> I believe the original thesis was whether "wing" paddles were more 
> efficient
> than traditional Euro paddles (ones with an oval-shaped  blade on the 
> end of
> a shaft).  Whether a low pressure area is created behind the paddle as 
> it
> slices through the water may be moot if other features of paddle 
> passage
> through water are less efficient.

The original thesis as I understood it included the idea that a paddle 
could be 100% efficient. My goal has been to disabuse that notion.
>
> I think, to advance the cause, we need __data__ to sort out what's 
> going on
> in this system.  It is too complex to discuss piecemeal or to solve by
> gedanken analysis.  Albeit, it has been fun to scan what you guys have 
> been
> writing.

There is some good data about the relative efficiency. The wing paddle 
is apparently about 89% efficient and the "conventional" paddle blade 
is about 74% efficient. What is still an open question is why the wind 
paddle is more efficient. 
http://www.isbs98.uni-konstanz.de/fullpaper/FullRossSanders.pdf What 
this means is that even with an efficient wing blade, 11% of all the 
energy applied to the paddle goes to do things other than pushing the 
boat forward.

Nick Schade

Guillemot Kayaks
824 Thompson St
Glastonbury, CT 06033
USA
Ph/Fx: (860) 659-8847
http://www.guillemot-kayaks.com/

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