Problem solved!!! I had been thinking about the various ways one could easily and accurately measure the kayak/paddler efficiency in real conditions over the last few days as discussed on this list. I have come up with what I think is an excellent way to accurately measure a whole variety of variables with two simple devices, which can be purchased or made from available materials, and a stop watch. My method could be used to accurately measure the difference in hulls at both cruise, top, and "burst" speeds since the difference is important. This is because it is clear from Matt's posting that the same hull which has the lowest drag at higher speeds do not have the lowest drag at cursing speeds. Because it has also been measured before that the same hull which has the lowest drag in calm seas is not the one with the lowest drag in rough conditions, my method could also be used to measure this difference as well. In considering everyone's useful comments and ideas, and in discussions before with Matt and others about this, it is pretty clear you have to take into account he whole human/paddle/kayak combination in real conditions if the test is going to be valid, including the lost effort in keeping the boat on course and perhaps upright in cases of really tippy kayaks in rough seas. Doing tank tests or towing tests you could be overlooking very important variables, including the skill of the paddler since it could be that a less experienced paddler my be better off with a different paddle and hull combination than a very experienced one (if fact I would suspect this would be the case). So even finding the lowest drag hull in an artificial test does not mean that is the best for an individual in the type of conditions they would be using it in. By taking measurements of performance including the human, you get all the known and unknown variables factored in automatically. THE METHOD The test would require you to measure the oxygen uptake of the paddler going a constant speed for a fixed amount of time (or distance). Measuring the oxygen uptake is done with a simple device used in physiology labs and even some sports clinics, it is a face mask with a flex hose that draws air through a calibrated fan-like device called an anemometer. There are both mechanical ones and now battery powered electronic ones with data ports. The more air consumed during the test the more muscle energy is expended in direct proportion to the amount of power out put. The other important component is to be able to accurately measure hull speed instantly and in real time relative to the water. This is important because the paddler has to be able to maintain a constant steady state speed during the test period. If the speed measurement is not continuous and instant you will not be able maintain the test speed accurately. Drag goes up exponentially with the speed, and power consumption goes up even faster than that, so using average speeds could results in large errors. You compare the air consumption using the same paddler with the same paddle in the same type of sea and wind conditions over a ten minute test period at a steady state speed. The paddler should maintain the speed for three or four minutes before the test starts to stabilize all the processes and using the same stroke, he hits the timer and zeros the air uptake measurement, and then paddles steady for ten minutes. He would then quickly record the amount of air consumed at the end of the test period. If you really want to get fancy here you can use a digital knotmeter and oxygen uptake instrument and plug them into a palm pilot or laptop computer to record the readings, and you can even include the heart rate and perhaps the body temperature (rectal thermometer anyone?). This would allow you to do automatic data collection and data reduction to get instant results. Though from my personal experience with doing a lot of testing I would prefer simple mechanical devices and manual data recording since it reduces the risk of breakdowns and other complications. Though if you did this kind of testing a lot then automatic data recording and reduction would save a lot of time, so setting it up and debugging it might be worth the effort. You could take the average of the best 3 out of 4 runs (or better the best 3 out of 5) to eliminate spurious errors. Then you could do the steady state runs at say 3, 4, 5, and 6 knots for each hull. Of course if you are interested only in efficient cruising you simple do it at your cursing speed. You could also use this method to measure which hull has the best 'burst' speed over a three minute run by maintaining a high speed for the shorter time. You would also want to start with a warmed up paddler and try to keep the rest period between runs about the same. And perhaps even have him drink and eat the same small snack between each run so he does not become depleted (like a cracker and 8 oz of water). You could do the same thing with different paddles using the same hull at each run. And you could try using different strokes styles with each paddle type. There are endless combinations, you just want to only change one thing at a time so you know what you are measuring. (I have seen tests where they kept changing too many things between each test and they did not know what they were measuring, a big mistake, and easily avoided). THE TESTING EQUIMENT The air uptake measuring device is used to measure an athlete's performance on a tread mill or stationary exercise bike and is common enough equipment in universities and sports clinic with physiology labs. There is a direct correlation with oxygen consumption and power out put with all individuals, unlike the heart rate which varies from individual with size and blood volume. If you can not afford to purchase one, or borrow one from a university (you might even get a Ph.D. candidate to assist you so he can publish the results as part of his studies), than they actually are not that hard to make from a common respirator mask and a few items from a bike or hobby shop, and a hardware store. A home made one would not be calibrated of course but that is not important as long as your are comparing the difference between hulls with the same device and the same paddler. The same is true with a knot meter, they can be purchased or a simple one made from readily available components. Calibration can be done with a GPS or a borrowed knot meter. (With the GPS you would have to make sure there is no current while doing the calibration runs). Of course it is not even that important to calibrate a homemade knot meter if you just want to know which hull has the least amount of drag at a comfortable cruising speed. You simply need the be able to keep a constant steady speed for the test, not necessarily know the absolute speed. If anyone is going to do this kind of testing and wants to know how to make a air uptake measuring device or a knot meter from purchased components email me off list and I'll give you instructions. Though purchasing these things will save a lot of tinkering around getting everything working. TYPE OF TESTS This type of test can also be used to measure which hull is best in either calm or high winds, and even in cross winds since it is likely that different hulls will have poor performance in cross wind if the paddlers has to expend a lot of energy keeping the kayak on coarse in a cross wind. You can also use it to see how much that piece of ju--....(err, excuse me) a rudder (or skag) up or down costs you in drag. This method could also be used to measure paddle efficiency at cruise or top speed (no doubt the same paddle will not be best for both), to test different types of strokes for efficiency, it could even be used to test the performance of different paddlers, or even different groups of paddlers as in experience, intermediate and beginner skill level. It is entirely conceivable that the most efficient kayak for a beginner is the most efficient for an experienced paddler. There is an endless combination of things you can compare, you simply keep all the variables constant except the one parameter you are comparing. We could publish articles using this method, compare hulls or paddles or whatever, and in the article propose to establish an industry wide standard that could be replicated anywhere by anyone with these two devices that can be purchased or made from locally available materials. If you have a "baseline" test that anyone can use than you have a way of comparing tests done by different people in different parts of the world with different test equipment. This way anyone can experiment and make meaningful comparisons with the published data. Therefore I would make the immodest proposal that this type of test be called the "Chopelas Method of Performance for Human Powered Watercraft" [that is pronounced "chop-ell-ess", and yes it is Greek in origin and quite old according to family lore]. Actually I would prefer something more like "the Oxygen Uptake Method..." since it is more accurate. Actually I did not invent this method to measure human performance, but as far as I know I have never seen used this way to actually measure human powered water craft performance. So what do you say Matt? Lets start getting the gear together and plan a test of a bunch of different hulls, paddles, etc. some time soon. Peter *************************************************************************** PaddleWise Paddling Mailing List - Any opinions or suggestions expressed here are solely those of the writer(s). You must assume the entire responsibility for reliance upon them. All postings copyright the author. Submissions: PaddleWise_at_PaddleWise.net Subscriptions: PaddleWise-request_at_PaddleWise.net Website: http://www.paddlewise.net/ ***************************************************************************Received on Sat Mar 10 2001 - 21:41:22 PST
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