RE: [Paddlewise] Tug of war. Where is the trick?

The video is very impressive, but something hits my thoughts. I have
raced (some years ago, Virginia 2000) a Mirage. I was not impressed by
the final speed. I was pretty close in a slow Hydrobike. Novice kayakers
were even and some more skilled beat the Mirage. Of course it appeared
to depend on the user, but, considering the tremendous difference in the
video, I don't think the rider would make that big a difference.

I think the point is that in the tug-of-war the Mirage power output is
all used in propelling (Its efficiency is optimum at standing still). On
the kayak at rest the paddlers efforts go in displacing water to the
sides of the paddle (its efficiency is worst at rest). The opposite
happens at full speed. The paddle power is used just to displace the
boat with little side water displacement, since the paddle stays (more
or less) in the same spot and the kayak has some inertia. So most of the
power goes to defeat water friction on the hull, and to keep momentum.

On the other side, at speed, the Mirage finns move against moving water,
and assuming the strokes pace is the same as in the stand still
condition, then the water pushed is less and less, the faster the boat
goes, because water is already moving away from the finn. The pressure
that the standing water put on the finn to give maximum force is much
less with water displacing backwards. The rider can increase his pace,
but there is a human endurance limit, and therefore the power efficiency
decreases with speed.

Therefore I suggest a test in which Gregg Barton and the Mirage rider,
in identical boats, pick up speed and pass the starting line at the same
time. I can bet that the kayaker will win in a sprint and in a long
distance run.

The video is a very clever way to show the Mirage power, but tug-of-war
is not the usual way to use human powered water vessels.

Best Regards,

Rafael
El caycuochief
Mexico
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