Uh oh - I've missed something basic again. What is "aspect ratio" as it applies to paddles? I need a really basic, practical description. This is a new concept to me - ove which has probably been explained in group postings and which I either overlooked or never understood in the beginning. - Bill Hansen *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
>Uh oh - I've missed something basic again. What is "aspect ratio" as it >applies to paddles? I need a really basic, practical description. This is a >new concept to me - ove which has probably been explained in group postings >and which I either overlooked or never understood in the beginning. We call the ratio of blade length to blade width the aspect ratio. Aeronautical engineers use the term in describing the characteristics of wings, propellers etc. Paddles with narrow long blades have high aspects ratios and paddles with short wide blades have low aspect ratios. The use of the terms "high" and "low" lack precision but work well enough when people have some familiarity with the object under discussion. Most paddlers would call a paddle with an aspect ratio of approximately 4:1 or less a low aspect ratio paddle anything above a high aspect ratio paddle. Nit pickers might prefer a moderate aspect ratio range as well. The aspect ratio primarily affects lift and drag. In general, higher aspect ratios generate greater lift with lower drag and low aspect ratios generate greater drag with less lift. So, the ideal aspect ratio for a paddle depends upon how it will get used (stroke mechanics). Ideally one would try to achieve the greatest thrust per unit area to minimize the paddle size. Sail boat designers have a similar challenge in designing sailing rigs. For windward work they seek to reduce drag but increase lift. For off wind work they increase drag (spinnakers etc.) and try to optimize both drag and lift. Cheers, John Winters Redwing Designs Specialists in Human Powered Watercraft http://home.ican.net/~735769/ *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
From: "John Winters" <735769_at_ican.net> To: <paddlewise_at_lists.intelenet.net> Subject: Re: [Paddlewise] aspect ratio? Date sent: Wed, 7 Apr 1999 06:19:00 -0400 > Paddles with narrow long blades have high aspects > ratios and paddles with short wide blades have low aspect ratios. The use > of the terms "high" and "low" lack precision but work well enough when > people have some familiarity with the object under discussion. > Another way to think of it is that aircraft like sailplanes --- gliders --- have very high aspect ratio wings, long and thin, as does the U-2 spy plane; can go high, stay high with little fuel expended. Not fast, but tremendous endurance. Like the Greenland paddle. And then there's helicopters --- long, thin wings that you whip around over your head --- on your rotorhead, that is --- to achieve lift. Not fast, but surprisingly efficient. Igor Sikorsky called it a rotating wing assembly, and Sikorsky drawings still refer to it in this term. Fascinating, huh? And all this based on Greenland paddles! Actually, I was hoping Professor Inverbon might have some interesting etymological information on the derivative of the word "Toksook". Jack Martin *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
Jach Martin wrote: > fast, but surprisingly efficient. Igor Sikorsky called it a rotating > wing assembly, and Sikorsky drawings still refer to it in this term. > Fascinating, huh? And all this based on Greenland paddles! Actually the rotating wing assembly that inspired the helicopter was invented by the Spanish inventor De La Cierva. He invented the autogiro in the first half of this century--an aircraft almost identical to the helicopter except for that the engine moves a front propeler, not the rotor. As most Europeans know, Spain is the favorite summer vacation country of most northern cultures. Thousands of Sweedish, Norwegians, Icelanders, Finnish, Germans, British, Danish, etc, move to Spain during the summer. Not surprisingly, the warm shores of the Spanish Mediterranean shore are also the favorite summer residence of the Greenlanders. They would take their paddles with them every summer. Strong evidence suggests that De La Cierva borrowed a few paddles from the Greenlanders, during a summer vacation, to make the rotor of his autogiro. The presence of Greenland paddles in the Mediterranean has had other consequences. The Medici also spent their summer vacation in Spain attracted by the beutiful Nordic blondes that take sun baths on the beach with minimum attire. They noticed the highly efficient Greenland paddles and took the idea back to Venize for their gondolas. Hence the long tradition of long narrow blades of the gondoliers. - Julio *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
Jack wrote; >Another way to think of it is that aircraft like sailplanes --- gliders --- >have very high aspect ratio wings, long and thin, as does the U-2 >spy plane; can go high, stay high with little fuel expended. Not >fast, but tremendous endurance. Like the Greenland paddle. And >then there's helicopters --- long, thin wings that you whip around >over your head --- on your rotorhead, that is --- to achieve lift. Not >fast, but surprisingly efficient. Igor Sikorsky called it a rotating >wing assembly, and Sikorsky drawings still refer to it in this term. >Fascinating, huh? And all this based on Greenland paddles! One has to use care when applying this kind of thing. For example, gliders require high lift but low drag. The use of paddles more closely resembles sailing on a broad reach where one wants to maximize thrust. In so doing one seeks to optimize both drag and lift components in which case a lower aspect ratio paddle ala the racing wing paddle has greater efficiency. This all ignores the further complication of wave making. Applying the helicopter rotor also falls short since they work as high speed lifting foils. The low speed, low load ship propellor fits the paddling model more accurately. One can see the differences in applicatioin by comparing high speed ship propellors and low speed ship propellors. High speed propellors generally have higher aspect ratios. Mind, super cavitating propellors alter circumstances but not many paddlers I know can cause supercavitation with a paddle and I sure wouldn't want to tick a person off that could. :-) In any case, I don't think the high aspect ratio paddles of the Arctic influenced either since the objectives differ so much. Cheers, John Winters Redwing Designs Specialists in Human Powered Watercraft http://home.ican.net/~735769/ Actually, I was hoping Professor Inverbon might have some interesting etymological information on the derivative of the word "Toksook". Jack Martin *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
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