> Why is it sometimes said that a Greenland padde which is > symmetrical in cross section will generate lift. Isn't the flow over > each side of the blade the same when sliced sideways? "Only if the angle of attack is zero degrees. Any airfoil will generate lift if it has a positive angle of attack." Thanks Dave, and for the Wikipedia reference, which I have now had a chance to read. Sticking point (punny about that) in my mind is that an airfoil is assymetric in section, and a greenland paddle is symmetric. So why would a GP act like an airfoil and generate lift in a direction away from the back of the blade? Or is that not what is meant when a GP is said to generate lift? I understand a wing paddle, which is a foil, generating lift away from the back of the blade, but a GP? *************************************************************************** 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/ ***************************************************************************
On Dec 4, 2007 4:20 PM, Peter Treby <ptreby_at_ozemail.com.au> wrote: > I understand a wing paddle, which is a foil, generating lift away from > the back of the blade, but a GP? > Think of the paddle in terms of a horizontal rudder. Craig Jungers Moses Lake, WA *************************************************************************** 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/ ***************************************************************************
" I understand a wing paddle, which is a foil, generating lift away from the back of the blade, but a GP? " " Think of the paddle in terms of a horizontal rudder. " Still can't see that the paddle / horizontal rudder acts as a foil. Does make me wonder what an asymmetric foil cross-section greenland paddle would be like. A sort of high aspect ratio wing paddle; a cheat stick for Greenland championship racing? *************************************************************************** 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/ ***************************************************************************
Asymmetry is not required to generate lift. Try thinking of stunt planes that fly up-side-down. I don't know if they have asymmetrical foils, but they can fly wheels upward or downward because lift is a matter of angle of attack. The standard canted greenland paddle stroke has a downward angle of attack, so if when they do create lift, much of the effort is in a downward direction, not forward. You could make an asymmetrical foil shape on a GP that could optimize the lift, but to get the most out of it you would need to perform a wing-paddle style stroke where the paddle flares sideways away from the boat, instead of downward as in the canted stroke. On Dec 5, 2007, at 1:39 AM, Peter Treby wrote: > " I understand a wing paddle, which is a foil, generating lift > away from > the back of the blade, but a GP? " > " Think of the paddle in terms of a horizontal rudder. " > Still can't see that the paddle / horizontal rudder acts as a foil. > Does > make me wonder what an asymmetric foil cross-section greenland > paddle would > be like. A sort of high aspect ratio wing paddle; a cheat stick for > Greenland championship racing? > 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/ ***************************************************************************
"Asymmetry is not required to generate lift. Try thinking of stunt planes that fly up-side-down. I don't know if they have asymmetrical foils, but they can fly wheels upward or downward because lift is a matter of angle of attack. " Then try thinking of why the stunt plane does have an asymmetric foil wing, with an upside and a downside. When flying in the wheels down orientation, the foil wings are generating lift by virtue of the longer upper surface creating a relative vacuum. When flying upside down, the lift is generated only by angle of attack. I think there may be a difference between these, which leads me back to the symmetric cross section GP. I still wonder whether there is any foil type lift operating, as seems to be claimed sometimes. *************************************************************************** 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/ ***************************************************************************
On Dec 5, 2007, at 3:31 PM, Peter Treby wrote: > I still wonder whether there is any foil type lift operating, as > seems to be claimed sometimes. I have heard claims of lift created like a wing, but not so much like a "foil". I guess it depends on your definition of a foil. Sticking your hand out a car wind you can feel lift. I don't know that your hand is a very good foil, or even a much of a wing, but it is still able to produce some lift. I am certain a GP can produce lift. Is it the optimum shape to produce lift? Probably not. Would an asymmetrical shape potentially produce more lift? Probably yes. But there is already a very good paddle that does this, it is called a wing paddle. I am not sure what you are trying to get at. If you want a paddle that works like a wing, why aren't you talking about a wing paddle? They work very well. 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/ ***************************************************************************
"I am certain a GP can produce lift. Is it the optimum shape to produce lift? Probably not. Would an asymmetrical shape potentially produce more lift? Probably yes. But there is already a very good paddle that does this, it is called a wing paddle. I am not sure what you are trying to get at. If you want a paddle that works like a wing, why aren't you talking about a wing paddle? They work very well." I'm trying to "get at" why a GP is said to generate lift. I'll go for a paddle rather than wasting any more keystrokes. *************************************************************************** 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/ ***************************************************************************
On Dec 5, 2007, at 5:26 PM, Peter Treby wrote: > I'm trying to "get at" why a GP is said to generate lift. I'll go for > a paddle rather than wasting any more keystrokes. Take a look at http://www.grc.nasa.gov/WWW/K-12/airplane/foil2.html Select "ellipse" as the foil shape, you will see that symmetrical shapes generate lift just fine. Any shape with an angle of attack is capable of generating lift. If someone has implied to you that a GP is somehow unique in this, they were incorrect. The beauty of complete symmetry is the lift will be the same going forward or back, up or down. 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/ ***************************************************************************
Nice analogy, Nick. I am going to use that ;-) The canted GP stroke also generates lift on the exit in the push phase of the canted stroke. Peter, the GP is the indigenous wing blade! it is happiest when you present one edge first, with the blade at an angle to the direction of the stroke. If you present it square and try to power that catch, it will flutter seeking one edge. And you can use the blade with a modified stroke that you would understand as wing stroke with the blade flipped over to the other edge, with the stroke away from the kayak. I have never seen Greenlanders use this stroke, but I have experimented with it and it works. It is a lot of work however. You better have a good engine. Turner On Dec 5, 2007, at 9:23 AM, Nick Schade wrote: > Asymmetry is not required to generate lift. Try thinking of stunt > planes that fly up-side-down. I don't know if they have > asymmetrical foils, but they can fly wheels upward or downward > because lift is a matter of angle of attack. > > The standard canted greenland paddle stroke has a downward angle of > attack, so if when they do create lift, much of the effort is in a > downward direction, not forward. You could make an asymmetrical > foil shape on a GP that could optimize the lift, but to get the > most out of it you would need to perform a wing-paddle style stroke > where the paddle flares sideways away from the boat, instead of > downward as in the canted stroke. *************************************************************************** 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/ ***************************************************************************
On Dec 5, 2007, at 11:43 AM, Turner Wilson wrote: > > And you can use the blade with a modified stroke that you would > understand as wing stroke with the blade flipped over to the other > edge, with the stroke away from the kayak. I have never seen > Greenlanders use this stroke, but I have experimented with it and > it works. It is a lot of work however. You better have a good engine. I know that some people do use a wind stroke with a GP. I've tried it and I agree that it requires a better engine. Unfortunately, it is the nature of efficiency that it feels harder. It takes a better engine because more of your effort goes towards moving the boat forward. Most people could probably paddle all day if they just dip their finger in the water, but most of the effort would go into stirring the water, not much would go to moving the boat. A less efficient paddle generates less force because your paddle is following the path of least resistance and moving water around. It moves a little bit of water fairly fast. The water is easy to move but doesn't contribute as much as it could to moving forward. If you grab ahold of more water and don't moving it as fast it will feel harder. Efficiency feels harder because you are putting more of the effort goes into making the boat go faster, and the faster you make the boat go, the more drag you need to overcome. You start to get farther into the inefficiency of the boat. Going faster takes a better engine. Nick 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/ ***************************************************************************
I certainly know nothing about paddle design or physics, but I have paddled a lot. And no paddle "sticks" in the water the way my traditional paddle does. It makes the water feel like cement. I use a rather "wingy" stroke but lower to the deck. I had always guessed that this solid feeling was due to a wing effect. Now I know. Thanks for an interesting discussion. Jim Tibensky *************************************************************************** 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/ ***************************************************************************
On Dec 6, 2007, at 8:17 AM, James wrote: > I certainly know nothing about paddle design or physics, but I have > paddled a lot. And no paddle "sticks" in the water the way my > traditional paddle does. It makes the water feel like cement. I > use a > rather "wingy" stroke but lower to the deck. I had always guessed > that > this solid feeling was due to a wing effect. Now I know. Have you ever tried a wing paddle? They do something a little beyond the fixed-in-cement feel. The blade actually exits the water ahead of where it enters. It is like concrete that is moving forward and requires a bigger engine to maintain a comfortable cadence. A blade specifically designed to maximize the lift effect will make a difference, but as you have noticed, the blade doesn't need to be an idealize foil shape to benefit from lift. Nick 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/ ***************************************************************************
Amateur conjecture: An asymmetric airfoil produces lift away from the higher side of the foil when moved through a fluid. This is due to the relative low pressure on that side. A symmetric blade at an angle of attack produces lift away from the back side of the blade due to relative low pressure on that side of the blade, because of turbulance. "... if the paddle is flat on one side and slightly curved, edge-to-edge, (symetric edge-to-edge, uniform curve) on the powerface" Does anyone make Greenland paddles asymmetric (one side flattish, other more curved)? Did Greenlanders do that? Some Aleut paddles are flat one side and ridged the other, was that for a foil effect? Do we know which side of such an Aleut paddle was the power face? "...it is the nature of efficiency that it feels harder." A stroke that feels harder can also be less efficient. E.g.(as you know), a stroke which carries too far past the paddlers body can feel hard because the blade "lifts water" at the end. Putting that the other way, a more efficient stroke feels easier, for the same boat speed. Hmmm, perhaps I've just defined efficiency by the definition of efficiency! Pleasing that this thread has created the "Greenland Horizontal Wing Rudder". That will add to paddling enjoyment next time the GP is used. *************************************************************************** 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/ ***************************************************************************
On Dec 7, 2007, at 1:05 AM, Peter Treby wrote: > Amateur conjecture: An asymmetric airfoil produces lift away from > the higher > side of the foil when moved through a fluid. This is due to the > relative low > pressure on that side. A symmetric blade at an angle of attack > produces lift > away from the back side of the blade due to relative low pressure > on that > side of the blade, because of turbulance. The physics of lift are the same regardless of the blade form. The references John W. gave will get more explicit, but all that is required is that you redirect or turn the fluid that the "wing" is acting in. Shapes other than a flat plate can do this without an angle of attack, but they still create lift by deflecting the fluid. 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/ ***************************************************************************
--- Peter Treby <ptreby_at_ozemail.com.au> wrote: > Does anyone make Greenland paddles asymmetric (one > side flattish, other more > curved)? Did Greenlanders do that? Some Aleut > paddles are flat one side and > ridged the other, was that for a foil effect? Do we > know which side of such > an Aleut paddle was the power face? Dear Peter, The only Greenland paddles I've seen with asymmetric faces are a few Polar Greenland paddles from 1890s-1910. They are perfectly flat on one face with a high-arch cross-section. These perhaps should not be considered as what we call "Greenland Paddles" because they are recent imports to Greenland and bear no resemblance to what any modern GP enthusiast would consider to be a 'Greenland paddle.' To emphasize: I haven't seen any true Greenland paddles with asymmetrical faces (having seen and studied over 80 Greenland paddles spanning 400 years [the paddles span 400 years. . . not my study of them ;-) As for what face of Aleut paddles was the power face, I'm not sure that question is settled, but I prefer to use the ridged face as the power face. This preference is based on using replicas of two different Aleut paddles. Best, Harvey *************************************************************************** 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/ ***************************************************************************
Peter said: "... if the paddle is flat on one side and slightly curved, edge-to- edge, (symetric edge-to-edge, uniform curve) on the powerface" Does anyone make Greenland paddles asymmetric (one side flattish, other more curved)? Did Greenlanders do that? Some Aleut paddles are flat one side and ridged the other, was that for a foil effect? Do we know which side of such an Aleut paddle was the power face? ------------------------------------ I have seen two Greenland Paddles in museums that were flat on one side and gently curved on the other. I made a replica of one of those paddles. As expected, using the flat side as the powerface results in severe ossilation. Using the curved side as the power face results in a smooth stroke, no ossilation. No doubt that the powerface of the Aleut paddle is the side with the ridge. When I roll or scull using my "asymetric" (cross section) paddle, I do so with the flat side down. If you do a vertical scull with this type of paddle parallel to the edge of a swimming pool, the paddle very clearly pulls away from the edge of the pool even if the flat side of the blade is parallel to the edge of the pool (Zero degree angle of attack). Speaking of sewing Greenland paddles together, I have seen many cases where sections are held togther with sinew stitched through holes drilled through the sections. *************************************************************************** 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/ ***************************************************************************
"Peter will find the pages on erroneous lift theories useful. :-)" Yes indeed. Others deeply mystified in related areas: "the complete description of turbulence remains one of the unsolved problems in physics. According to an apocryphal story Werner Heisenberg was asked what he would ask God, given the opportunity. His reply was: "When I meet God, I am going to ask him two questions: Why relativity? And why turbulence? I really believe he will have an answer for the first." *************************************************************************** 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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