. Tord wrote; > But, the high aspect ratio wing works by having the flow chord-wise, > across the wing at right angles, which hardly is the case with a Greenland > paddle, rather the reverse, as most of the flow on a GP paddle is > spanwise, I wonder if this really applies. As I understand the stroke described by some who use High Aspect Ratio paddles the flow is across the chord as the blade slices in an arc from the surface to a more vertical orientation at the bottom of the stroke. If I have this wrong maybe the GP people can straighten me out. > Oars are pretty much like GP paddles, and the longer the blades the more > efficient I find them, till they get impractically long. And you can, on a > windless evening, easily see how much longer the vortices remain in > the water when using better oars! This is an interesting comment. When I was designing rowing shells just about every competitor had shifted over to the modern "hatchet" style of blade. I did not see any other type during the recent Olympics but then they didn't focus much on oars in the coveage. Have they gone back to the old narrow blades? Cheers John Winters *************************************************************************** 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/ ***************************************************************************
Nick wrote: >I frequently here people talk about paddles working like wings Aircraft wings create lift because air moves faster over the upper, curved surface of the wing therefore the air pressure decreases, creating a force that 'pulls' the wing upwards, ie. lift. So, I don't see how a forward-stroking Greenland paddle is similar to that of a glider wing in flight. Like you say, wings produce lift, not propulsion. Cheers Paul *************************************************************************** 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/ ***************************************************************************
A better analogy may be a propeller instead of a glider wing, but I still don't see it working as the Greenland stroke is described. With a prop, the blades are foil sections which produce thrust through lift. On Sep 7, 2004, at 12:33 PM, Paul Ash wrote: > Nick wrote: > >> I frequently here people talk about paddles working like wings > > Aircraft wings create lift because air moves faster over the upper, > curved > surface of the wing therefore the air pressure decreases, creating a > force > that 'pulls' the wing upwards, ie. lift. > > So, I don't see how a forward-stroking Greenland paddle is similar to > that of > a glider wing in flight. Like you say, wings produce lift, not > propulsion. > Nick Schade Guillemot Kayaks 824 Thompson St Glastonbury, CT 06033 USA Ph/Fx: (860) 659-8847 http://www.guillemot-kayaks.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/ ***************************************************************************
At 03:43 PM 9/7/2004 -0400, Nick Schade wrote: >A better analogy may be a propeller instead of a glider wing, but I still >don't see it working as the Greenland stroke is described. With a prop, >the blades are foil sections which produce thrust through lift. When describing how a paddle can produces lift, in the context of using the paddle when sculling for support or for a low/high brace turn, the analogy that I usually use is remembering what happens when you put your hand out the window of a moving vehicle. Holding your hand with your fingers pointing forward it's easy to feel the effect of raising or lowering your fingers. With just a very small raise of the fingers your hand and arm will move up. Raising the fingers more causes the hand not only to move up, but to move backwards as well. Lower your fingers and the hand dives. Translating that to the paddle, such that the angle of the paddle blade has the leading edge slightly higher than the trailing edge, and the paddle will produce lift, and thus support, for a sculling brace or high/low brace turn. Greg Stamer also presented an interesting idea when I did a training session with him a couple of years ago. He was talking about the exit portion of the stroke when using a GP. As a demonstration we stuck the paddle in next to our hip with the paddle at about a 30 degree angle. Then, rather than pulling back with the paddle we just lifted straight up. Although nobody was setting any speed records it was clear that lifting the paddle straight up with the paddle angled was producing some forward momentum *************************************************************************** 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/ ***************************************************************************
Nick Schade <nick_at_guillemot-kayaks.com> wrote: > I frequently here people talk about paddles working like wings and am > prepared to accept that it is possible. Yet whenever I ask people to > describe how the paddle is working like a wing, their explanations fall > flat. > People like to talk about how Greenland paddles are similar to glider > wings etc. But, they never seem to be able to explain how the motion of > a forward-stroking Greenland paddle is similar to that of a glider wing > through the air. I agree 100% with Nick, but is not incorrect when Steve Brown wrote: >High > aspect ratio wings have high lift-to-drag ratios, which is why they > are seen > on high performance aircraft. Low aspect ratio wings have more lift in > when > stalled so the transition from flying to stalled is less abrupt. This > is why > they are seen on trainer aircraft and aircraft that must operate off > short > fields. But, the high aspect ratio wing works by having the flow chord-wise, across the wing at right angles, which hardly is the case with a Greenland paddle, rather the reverse, as most of the flow on a GP paddle is spanwise, thus similar to the aerodynamic lift a Sidewinder missile produces from its body, a lift entirely dependent of vortices - a modern missile can pull 50 G's in turns, which no high aspect ratio wing ever will be able to, not least to their sudden stalls! So for the vortex system to start you have to push the paddle down and then pull backward (same as with a Euro paddle), but due to the GP's extremely low aspect ratio it eventually produces a more energized vortex, I would persume, than the Euro, that has more bite initially, but eventually have poorer vortex attachment, due to its shorter blade length. Oars are pretty much like GP paddles, and the longer the blades the more efficient I find them, till they get impractically long. And you can, on a windless evening, easily see how much longer the vortices remain in the water when using better oars! I think flutter is the restricting factor when it comes to oars, actually :-)! Tord *************************************************************************** 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/ ***************************************************************************
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