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Does Size Matter?
By Frank Biller
Although some might expect a discussion on body size and that rowers are tall, perhaps even going down the slippery slope of ergo scores versus on-water performances, sorry, I am sticking strictly to product discussions here.
Size of XL
With NK’s launch of the SpeedCoach XL series, a number of customer have raised concerns over the size of the unit, as well as its weight. We all know that lighter is probably better in rowing, especially when it comes to “dead weight”, weight that does nothing to improve boat speed. In many discussions with concerned customers over the past two years I successfully explained how perception and effect don’t always match. Benefits are often greater than perceived cost, and of course, coming away from what we are used to takes some time as well. Granted, an XL3 weighs about 7 ounces (200 grams), double the weight of a SpeedCoach Gold. To put it in perspective, that 3.5 ounces difference is less than the weight of that pre-row cup of coffee. Although it’s doubtful this will ever make the difference in a race, there is another aspect: benefits for training!
A junior/high school rower generally trains about 500 hours per year, an elite athlete about double that, around 1,000 hours per year (source: Volker Nolte, “Rowing Faster”). If we assume that about 3/4 of the time is spent in the boat and of which about 1 1/2 hours is pure racing time, we can conclude that only about 0.2% to 0.3% of an athlete’s time in the boat is spent racing. This means that rowers spend over 99% of their time working hard to get faster and improving technically. Wouldn’t you want the best possible tool to spend this time most effectively? Heck, if you do this 99% of the time right, you can race with a kitchen clock around my head and still be faster! Of course, we were delighted to see several boats racing with an XL at the Olympics even, probably not even 0.001% of their time in the boat in an Olympic year. And if you think it throws you off-balance, the silver medal Canadian pair had no problems mounting their unit on the starboard gunwale...
Impeller Size
Recently a smaller impeller was brought to my attention, that according to the manufacturer has a much better drag effect than our impeller. Always wanting to improve, we are of course interested. However, having seen it I was rather disappointed, smaller isn’t always better. Just like with coxswain minimum weights, there are limits to everything. We had similar experiences in our Kestrel Pocket Weather Meter side of Nielsen-Kellerman, where smaller impellers entered the market to measure wind speed. However, the significantly reduced size of the impeller fins (that makes it spin) are also prone to increased slippage and therefore more likely to produce inconsistent and inaccurate readings. In addition to the fin size other aspects are to be considered: Is there a high quality ball bearing inside the spinning part to allow consistent spinning? How is the finish of the impeller, is the entire surface perfectly smooth? Is the entire fin streamlined and optimized for laminar flow?
Another issue is where the impeller is placed. Since we absolutely want to avoid putting anything into the laminar flow of the boat near the bow, we are, in respect to drag, much better off in the turbulent layer, where the drag effect is less. However, in order to be able to measure the flow, the spinning part cannot be too close the hull either, as the turbulent flow changes drastically with the speed changes a rowing shell produces during a single stroke. And of course, the change of the profile of the boundary layer with increasing boat speed also needs to be accounted for, since it’s by no means a linear relationship.
Since we spend so much time training (see above) and accurate feedback is important, I cannot stress enough how a visual perception, for example size, can fool us when it comes to performance, accuracy and benefit.
So the answer to the question, “does size matter?” I would say “not always”.
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