From: Guillemot@aol.com
Date: Wed, 15 Mar 1995 19:48:17 -0500
Message-Id: <950315194424_50714384@aol.com>
To: baidarka@imagelan.com
Subject: Re: Traditional Paddles new thoughts
bblohm@hpbs1686.boi.hp.com (Bill Blohm):
> I think I might see a possible error here. I think the idea is good, but
> do you take into account the height of the paddler? For example, I don't
> know your height, but let's say you are 6' tall, and use N. Now take one
> of the old Aleuts, what was his height? Now with him using Z, which of you
> hasmthe longer paddle, WRT your height? Or do they now have the same
> effective length? This will modify the angle of attack somewhat in touring
> paddling, IMHO of course. There is more power in a sweep stroke, for
example,
> than in a stroke performed close to the hull. That's why I think perhaps
you
> need to also factor in the heights of the paddler as well as the lengths of
> the paddles to have a valid comparision. Make any sense to anyone else?
My numbers are full of "approximations" I choose not call them errors, that
doesn't change the fact that they are inaccurate. The numbers assume the
paddles rotate around a fixed point at the center of the paddle and the blade
is fully submerged. Neither of which is always true. With body rotation and
arm motion the axis of rotation moves and it is not really justified to refer
to an "axis of rotation". Then adding things like the sliding stroke and
differences in technique... Because I couldn't figure out a way to take any
of this into account, I did what any good engineer would do. I ignored it.
POOF! The problem is now easy.
I think the approximations will hold up because a good sea kayak technique
with a modern paddle is essentially the same as that with a traditional
paddle. Hands held low, not too far apart, etc. Techniques such as the
sliding stroke can be used effectively with modern paddles. Therefore, the
primary basis for comparison are blade area and effective length.
The size of the paddler will effect the calculations only in the way they
effect the size of the paddle. A larger paddler would probably use a larger
paddle. This would slightly increase the blade area and longer length.
kork@imagelan.com (Kirk Olsen):
> Cavitation of the blade, length of paddle stroke, and percentage of the
> blade submersed also need to be considered here. I find it rare that
> I use the entire blade on my greenland style paddle.
>
> Excessive force or an improper paddle plant lead to cavitation and wasted
> effort.
Any force use moving the paddle backwards is countered by an equal and
opposite force moving the boat forward. A poorly place, cavitating blade,
pulled straight back does not waste much effort. It is not as useful as the
paddler may have wanted but all the work use pulling the paddle is use to
propel the boat. (assuming the paddle and your arms, etc. don't require any
energy to move around:)
Energy is only wasted when the force is not applied directly parallel to the
desired direction of motion. Like Kirk says, ideally, the blade should be
place perpendicular and pulled parallel to the intended path. Any variation
from this will tend to waste energy.
I think differences in blade form such as spooning essentially change how
effective the blade area is at pushing against the water. This is not the
same thing as efficiency. One unit of force back results in one unit of force
forward regardles of whether it is applied with a spoon or pencil.
Nick