Monday, September 17, 2012

Paddle Dynamics

Three Greenland style paddles on display at the boat ramp where I just got done testing them. The breakdown paddle on the left had the tips thinned. The one in the middle had the varnish touched up. Note that the paddle in the middle has a more curved face than the one on the left which has a flatter, thinner face. The one on the right, the long one, is one I just finished carving.
I recently did some maintenance on two paddles for a client of mine.  One of the paddles was just worn and needed a little sanding and a coat or three of fresh varnish.  The other one was making noises in use because the tips were too blunt so I made the tips sharper.  Before returning the paddles, I took them out to test because that is the right thing to do when you make a repair and charge someone for it.
Oh yes, there was also a third paddle, one that was supposed to be a blank for a paddle making class that a prospective student's wife had given him as a Christmas present.  Three years or more passed and the student still hadn't managed to arrange a class date to finish the paddle, so I finished it just get the thing out of my shop.  And so while I was testing the other two paddles, I thought I would test this one as well.
Things got off to a slow start.  The boat I used for a test vehicle belonged to someone else and had very slack deck lines that made it hard to keep spare paddles on deck but after some experimentation, I managed to figure out a way to carry the spare paddles while testing.
Paddle testing for me is usually comparative.  Given my testing tools which consist of myself as motor and test evaluator, a gps as speed indicator, a kayak and some suitable body of water to float the boat and offer resistance to forward progress, the tests tend to be subjective and relative.  That is, I don't have absolute numbers at the end of the test.  I take several paddles, paddle back and forth and compare the performance of the paddles under more or less identical conditions.  The two things I can measure are speed and the amount of effort I put into paddling.  Effort is hard to measure so it usually means that I try to make the boat go as fast as I can with a given paddle.  And when I am going as fast as I can, I measure the speed with the GPS.
Usually what happens is that one paddle feels better than another or one paddle gives me a higher top speed than another.  And in general, results tend to be vague impressions more than anything rigidly scientific.  But some good can come out of even an unscientific test, as happened in this case.
Let me share my observations.
As expected with the three paddles pictured above, the long paddle gave me the best top speed. This paddle was 98 inches long.  The two shorter paddles were both 84 inches long.  Normally I like a paddle that is somewhere between 88 and 92 inches long so I expected the 84 inch paddles to be slightly underpowered.  As it turned out, they produced top speeds not that much slower than the long paddle.  Acceleration with the short paddles was lower than with the long paddle, but by and large, once I got the boat going, the short paddles did pretty well.
What was happening was that the hull speed of the boat was the limiting factor in the test and not the paddles.  That is,  the short paddles were adequate for getting the boat up to hull speed but couldn't push the boat much beyond that.  And that's probably adequate for most situations.  The long paddle with its greater blade surface could push the boat beyond its hull speed but at the expense of greater effort.
So the problem with testing paddles using a GPS and a slow boat is that just about any paddle can push the boat up to hull speed and further effort even with a larger paddle produces little extra speed so that measurement of top speed are more an indication of the boat's limitations than any measure of the paddle's effectiveness.
It would be nice to have a meter that could measure the speed of the boat, the resistance offered by the boat and the power needed by the paddler to keep the boat at that speed.  If such a thing were available, it would be able to offer a good comparative test of different paddles' effectiveness.  Even if two paddles were able to bring a given boat up to the same speed, the one that requires less effort by the paddler would be the better paddle.  However, since there is no good way to measure that effort, it is hard to make meaningful claims about the effectiveness of one paddle vs. another and the question of which of two paddles is the better one remains largely subjective.

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