Tinkerntom wrote:

Force on the paddle shaft, at the handgrip.


Makes me think of a big torque wrench. Do you get any deflection of the
paddle shaft while paddling? Use a smaller shaft until you do, Take
video, or measure the deflection of the needle! Then in the lab,
measure the force needed to duplicate the deflection. You should then
have an idea of what the possible force exerted on the shaft would be
for a particular paddler.

The potential force would be based on as wolfgang points out the
effectiveness of the engine mount, the paddlers seat and feet, the
grip, and other loss of efficiency factors that could be isolated for
significance. TnT


The problem is not how to measure the moment (torque) on the shaft.
Strain guages have been around for ages that will allow me to do that,
and I'm well familiar with how to implement them. The problem is
determining power from that force.

The force balance in the kayak system is weird, as there is no fixed
pivot point on the paddle. So, the pivot point is a "virtual" one.

I'm making progress, but still wonder if anyone has done this already.

The only way I can see to determine power at the hand grip is to record
3D kinematic video of the motion, so that the actual 3D vector of the
handgrip velocity is known. Then Power=FxV. But I wonder if there's a
better/simpler way to do it.

I did find a paper (Aitken, 1992) that measured paddle shaft torque
(bending) with strain guages, then used the hull velocity through the
water to get power. I don't see how this is valid, though, since hand
velocity is not equal to hull velocity. But then I suppose it would
depend on what your frame of reference was... Hmmmm....

Any other bright ideas out there? :-)

-Kieran