Allan Bennett wrote:
In article j1tUd.66306$8a6.13749@trndny09, Kieran
wrote:

That's the general idea, but because the paddling motion is 3-d, it's
not very easy to determine power just from the strain in the paddle
shaft.


The flex in a paddle-shaft will be a reflection of all the forces acting upon
the blade in the water. Using the force profile: t v deflection) and
suitable calibration, it will be possible to determine the power.

Hmmm... this seems to be the part I'm missing. How do you get power
without knowing the path of the force?

You need to know instantaneous velocity (direction and magnitude) at every
moment. In a fixed-pivot environment like rowing, you can just put a
potentiometer on the oar-lock. But the kayak/canoe paddle has no fixed
pivot point. So, I imagine that a virtual pivot point would have to be
derived via 3-d kinematic video analysis.


It seems there is a virtual point (see Plagenhoef, 1979 and others), just as
there is a virtual point where all the forces that propel the boat seem to
meet - a valuable tool for those athletes with adequate imagination.

Thanks for the reference. I'll see if I can find that publication.
Would that be a book or a journal article?

I haven't yet sat down and done a free-body of the system, but in my
head, it seems like it's going to be an indeterminant system... not fun.


..and the ultimate purpose?

Trying to come up with a master's thesis for my degree in biomechanics.
A research prof here has an ongoing project that considers at a high
(systems) level the energetics of different forms of human locomotion
through/in/on water, including surface swimming with/without fins,
submerged (e.g. scuba) swimming, rowing, and kayaking. There's very
little published research that we can find on kayaking, so that's the
part I'm tackling.

Thanks for your input!
-Kieran