Re: [Paddlewise] (un)Feathered paddles in surf

Matt wrote;


>
>
>True, but I doubt way out at the paddle blade (at least when it is at the
>angle most effected by the wind) ones body has much effect.

According to my information effect extends up to 2.5 times the chord width
of the object in the flow. In this case probably 5 feet or so for a human
body. Mind it diminishes with distance.

(SNIP)
>Since the paddle is most effected when it is perpendicular to
>the wind

Not necessarily so unless you mean that the drag reaches its maximum. The
effect of the adjacent body increases with proximity as well as orientation
to the flow.


>and since one paddles with the paddle out in front of the body, if
>the flow is altered by the body way out to the paddle blades it is more
>likely to be deflected at the paddle blade when the wind is from behind
the
>body and the paddle is therefore further downwind. Since an unfeathered
>paddle is also deflecting the wind it is possible (especially near the end
>of a stroke) that the upper blade (angled forward like a scoop) is
>deflecting some wind into the paddlers wind catching body to some extent
and
>this might further slow the paddler down.

Interfering bodies do not necessarily have additive drag but influence each
other. This provides the explanantion for why solo paddlers have so much
less efficiency than tandem paddlers when paddling against the wind. The
aft paddlers creates less drag because he lies in the forward paddler's
turbulent wake. The same applies to paddles and paddler. Thus the drag of
the paddle can reduce the drag on the paddler producing less net drag than
if the two bodies get treated individually. In the case of the untwisted
blade, the total drag on the system could be quite similar to that of the
twisted blade. If anyone out there has a copy of Horner's Fluid Dynamics
they can check this out as I recall there being some discussion of the
various research papers on this topic. My own copy is out on loan so I will
have to wait a week or two to check it out myself.


>True again, but since the blade angle is also smaller at that time so is
the
>effect of the wind on it then. I expect whoever we tempt into figuring out
>the added drag into a headwind due to using an unfeathered paddle will
take
>the time the blade spends at various angles to the wind into account.

I doubt if we will tempt anyone into this. :-)

An interesting simple test might involve nothing more exotic that some
light tell tales atatched to paddle and paddler to provide visualization of
the flow. This won't provide any quantitative information but could provide
some interesting insight. Maybe I will get time to try it this weekend.
Unfortunately I am involved with some other paddle research that has
developed some snags and free time evaporates during periods of confusion
and perplexity.

>The way feathered paddling is usually taught is a perscription for wrist
>problems and while paddling unfeathered is one cure pushing with a
straight
>wrist and a somewhat open hand also works and doesn't have the
disadvantages
>of unfeathered paddling (and those due to switching feathers on bracing
>skills) to contend with.

I developed my wrist problems from an number of other sports and the
twisted paddles aggravated it. Not being an expert in biomechanics and
sports medicine I had to seek out a solution that worked rather than one
that fitted my theories. As long time readers of Paddlewise and WaveLength
know, I have supported the "twisted paddle is best" from a theoretical
basis for years. Unfortunately theory and real life collided and I chose to
adopt the "at hand" solution. Occasionally I go back to my wind paddle but
not for long. Just not man enough I guess.



>How did you judge which was most efficient for you? Were you bending your
>"control hand" wrist back on the feathered push? Do you think you can
>convince top racers that if they switch to unfeathered they will be more
>efficient? I can't believe that Olympic teams haven't looked into this
>possibility, or would it just seem too far fetched for them to consider at
>all? Maybe they are missing the boat here.

The efficiency comes from not being able to paddle due to the pain of using
a twisted paddle. Having been taught by a past world champion K-1 paddler I
suspect that I got pretty good instruction. His verdict was that I was
better off with an untwisted paddle. But then, he may not have seen any
profit in spending time with me since at 45 years I had no Olympic
potential.

I may not have made myself perfectly clear earlier. My arguement has
nothing to do with the relative efficiencies of the two styles but rather
the relative efficiencies of the two style when applied to individuals. The
dogmatism of using one over the other seems ill advised when applied to all
paddlers.



Cheers,
John Winters
Redwing Designs
Specialists in Human Powered Watercraft
http://home.ican.net/~735769/



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