I notice we're having a sort of a replay of a discussion from some months ago, and some of the disagreements seem to be coming from some of the same misunderstandings and miscommunications. There are a number of issues that are easily confused- human efficiency and paddle efficiency, for instance. The term "efficiency" often gets used for both. We have to be careful to seperate the two. "Slippage" is another confusing term. A paddle that has less resistance than another when pulled thorough the water- some would call this greater slippage- isn't necessarily less efficient at turning human effort into propulsion. The highest overall efficiency occurs when the greatest amount of human effort is translated into propulsion- and even then we can talk about efficiency in the short term versus long term, efficiency at high speed, versus low speed and on and on. If you look at propellors for aircraft and boats (and house fans for that matter) you see that the area, aspect ratio, and pitch of the blades have to be optimized for the engine, the velocity of the craft, the relative density of fluid it operates in and so forth. Helicopter blades are very different from paddlewheels ;-) And then you have other complicating factors. For instance, "Harlold" writes: >>You occasionally see extreme examples of this where a powerful paddler pulls >>a massive stroke and then pauses for a long glide before taking another huge >>pull on the water. The inefficiency of this style is pretty obvious as his >>boat lurches forward and then settles back down into the water. >> >>On the other hand, you see Greg Barton churning away with very high cadences >>and very short strokes, leaving the big-bite Neanderthal days behind. >> >>Can the efficiency gained by this factor partially explain the discrepancy >>which is bothering Matt? >> > > Part of this is that drag increases exponentially with velocity. As Harold observes, the paddler who takes a big stroke and then rests is alternately pulling his boat into a region of higher drag and consequently less overall system efficiency. And yet there may be paddlers and boats for whom this is an optimum technique. (I'm not saying there is definitely such an example, only that it is possible). And that certainly doesn't exhaust all the factors. You can approach the analysis from many different points of view. My point, in the end, is that a long, high-aspect ratio traditional Greenland paddle is neither more or less efficient than a modern wing paddle or a stubby white water paddle. They're just optimized for different enviroments and applications. -- mike ------------------------- Michael Edelman medelman_at_ameritech.net http://www.foldingkayaks.org http://www.findascope.com *************************************************************************** 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 Thu Jul 25 2002 - 20:25:59 PDT
This archive was generated by hypermail 2.4.0 : Thu Aug 21 2025 - 16:30:56 PDT