RE: [Paddlewise] Paddling in Space

Peter O wrote:
<SNIP>>>>>>Wouldn't a paddle fitted with one or two 3 axis accelerometers
radio linked
to a data logger let you calculate this? And the centre of thrust move in
the paddle with time?
A friend fitted his paddle with a two axis accelerometer many years ago and
still has it available. We're talking about using it with TORSON to simulate
the forces involved in kayak injuries but I think 3 axis will be necessary.
I'm told this has already been done for rowing and running. Has it been done
for kayaking?<<<<<<SNIP>
Actually, years ago when I was working on this problem for John Dowd and
John Dawkins when Sea Kayaker was first thinking of doing kayak reviews
(1985) I wanted to put two strain gauges at 90 degrees to each other on each
side of the paddle shaft (between hands and the blade-4 strain gauges in
all). This should tell you the total force going into the paddle and its
direction of application too. What it couldn't tell you was if paddlers (or
a single paddler) was using a consistent stroke so in order to confirm the
accuracy of the results (and so the test paddler couldn't cheat on the test
without the testers knowing about it) I also looked into the kind of devices
that would measure rotations around each axis in order to know exactly where
the paddle was at all times. If I recall correctly besides the weight, bulk
and high price these items were then there also might have been a problem
with how fast they could detect and output data and their "slew" rate. Maybe
they are all small and light, fast, cheap and solid state now and we could
employ them to assure consistency of stroke (and for training) as well as
the strain gauges in our new test platform paddle. I know the analog/digital
converter and computer and storage of data have all been integrated into a
small and relatively cheap device since all being separate when I looked
into them back in 1985 or 86.
I'd like to hear about what your friend's paddle can do and more about why
he did it. I'm unaware of anyone doing this but suspect the U.S. Sprint team
would if anyone would have. I'll try to remember to ask Greg Barton about it
next time I talk to him. He's an engineer, makes paddles and already has a
distribution network and contacts with a lot of racers. I'll bet he is real
interested in the subject himself too. This kind of thing should be right up
his alley. Maybe I can get him interested in working on this.
I'd sure like to play with this kind of paddle. I think now most paddle
experiments are done by dragging paddles at a fixed angle through a water
tank and since this isn't rally how a paddle is used it would be better to
have an electronic paddle that you use like any other paddle while it
measures angles and forces every 1/10 of a second or so. Run a knotmeter
into the same computer and I think you could find out about the efficiencies
of blades, boats and paddlers by controlling the other variables and
measuring the effects of the one you are studying at the time. Imagine being
able to paddle different boats into the same head seas and wind and
comparing there performance with each other and with their calm water
performance. Considering the possibilities for improving the efficiency of
paddler, paddle and boat I can't believe the U.S. Sprint team hasn't tried
to do this already.

Peter asked:
<SNIP>>>>>>...could slippage be measured either by repeatedly
moving a paddle in a tank or in a current free lake and having a floating
line with equispaced markers tightly stretched along the paddle route and
videoing the progress of the paddle relative to the markers? Possibly put a
set of colored rings along the shaft of the paddle where it enters the water
to help.<<<<SNIP>

That would be easy. Put bright targets on the paddle shaft and blade edge
and using frame by frame stop action play of the video you could measure the
distance and the speed of the kayak with grease pencil marks right on the TV
screen. What I've yet to figure out is where along the paddle shaft do we
make the measurement that determines how much the paddle has slipped.
Assuming it is at the center of thrust (or even average center of thrust) on
the blade how do we find out where that is along a vertical axis so we can
measure the slippage distance of the paddle at that depth (or average depth)
on the TV screen.

Ralph, I was at the 1982 and 1984 LL Bean Symposiums. This kind of rings a
bell. Maybe that was me asking Derek about the practicality of seal
landings. The seal landing possibilities were a standing joke with Cam and I
whenever we looked at a swell washed shore during our paddles together on
the ocean coasts of WA and BC. I don't recall Derek getting hurt though, but
then I might not have been paying attention and missed it.

Matt Broze
http://www.marinerkayaks.com


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