To my knowledge no one has ever provided proof that one could apply steady state theory to paddles. Simply quoting steady state theory does not qualify as proof. Until some one can provide actual test data to support the assumptions that rthe esult of steady state flow is sufficently close to the pulsed flow of paddles then we cannot lend much credence to it. I suspect that a lot of the confusion comes from assuming the objective is high lift as opposed to high thrust per unit area. If we change the question from How do we generate more lift? to How do we generate more thrust we may get another answer. Another problem we should condsider in the quest for high lift has to do with the difficulty in maintaining any angle of attack through the water much less the ideal angle of attack. Can paddlers actually achieve and maintain the desired angle of attack? How does one compensate for the variability in angle of attack due to the ever changing flow direction in waves? (with the wave at the crest, vertical down on the front face, against the wave direction in the trough and vertically up on the back and, of course, everything in between) 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/ ***************************************************************************
I'm not even certain that we can get to the point where we can worry about angle of attack to achieve lift. Any kind of lift is going to require the paddle blade move perpendicularly to the direction of boat motion. This is either up-down or left-right motion. Paddlers arms are pretty short and don't allow much side-to-side motion (maybe 14 - 18"), and as long as we are sitting in the middle of a boat, vertical motion is limited. The largest range of motion available to a paddler is available by reaching forward and pulling back (about 3' to 4'). It is possible to push the blade out to the side a bit while pulling back, but the range of motion is substantially limited. There does appear to be some benefit to swinging the blade out away from the boat, but this may have as much to do with keeping the blade in "clean", undisturbed, still water as it does with generating significant "lift". Since it is so hard to move the paddle in a manner to generate thrust with lift, it would seem to be jumping the gun to analyze the virtues of different foil configurations. The only stroke I've seen that has the potential to generate lift is the wing paddle stroke, and it isn't even established they really benefit from lift. We can produce all kinds of equation demonstrating the benefits of high-aspect ratio, but if the blade doesn't move right, what is the point? Nick On Sep 9, 2004, at 12:43 PM, John Winters wrote: > Another problem we should condsider in the quest for high lift has to > do with the difficulty in maintaining any angle of attack through the > water much less the ideal angle of attack. Can paddlers actually > achieve and maintain the desired angle of attack? How does one > compensate for the variability in angle of attack due to the ever > changing flow direction in waves? (with the wave at the crest, > vertical down on the front face, against the wave direction in the > trough and vertically up on the back and, of course, everything in > between) 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/ ***************************************************************************
You can feel the paddle stall, or go deeper into stall. This is extremely intuitive as (once experienced) we constantly adjust blade angle to get the right bite. Like intercepting a fly ball, it's something any practiced child can do, but would cost millions to try and get a machine to do it. Steve Brown -----Original Message----- ....... How does one compensate for the variability in angle of attack due to the ever changing flow direction in waves? (with the wave at the crest, vertical down on the front face, against the wave direction in the trough and vertically up on the back and, of course, everything in between) 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/ ***************************************************************************
Steve wrote; >You can feel the paddle stall, or go deeper into stall. This is extremely >intuitive as (once experienced) we constantly adjust blade angle to get the >right bite. Do you have any tests that prove you can 1. detect stall and discern it from any other forces acting on the paddle and 2. Adjust the angle of attack rapidly enough to make a difference? By this I mean tests I can perform to verify or refute your claim. If not you will have to forgive me for my skepticism. According to people in the field of psychokinetics what you suggest might prove revolutionary. >Like intercepting a fly ball, it's something any practiced child can do, >but >would cost millions to try and get a machine to do it. Not sure eye/hand co-ordination has much to do with it. A for intercepting a fly ball, the US has has already spent billions trying to intercept missles. Maybe they would have better luck with the fly balls and for less money. :-) 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/ ***************************************************************************
Skepticism is healthy. Use a sculling brace to prove your paddle is a wing that can stall. When a wing is flying, increasing AOA increases lift. A stall is when increasing AOA does not increase lift. Continuing to increase it beyond that critical AOA will actually decrease lift. Drag, however, continues to increase with AOA. The AOA at which a wing stalls does not change with air speed, or the weight on the wing. Airspeed effects the lift a wing produces for a given AOA and the weight on the wing determines how much lift is required to keep it aloft.. The procedure for stall recovery in an airplane is to put the nose down (reduce angle of attack), use gravity (and full power) to regain airspeed (increase lift) so that the weight of the airplane can again be carried without exceeding the maximum AOA, and then level out. With a kayak paddle, a stall is most easily experienced when bracing. The procedure for stall recovery during a paddle brace is sculling. Effectively reducing the AOA, and regaining water speed across the blade so that adequate lift can be maintained without again exceeding the maximum acceptable angle of attack. Many, if not all on this list can easily manipulate their paddle during a sculling brace to prevent it from stalling. Too much AOA and you start kicking up tons of water (increased drag), but you still continue to sink (loss of lift). As you slow or speed up sculling, you will intuitively (once practiced) increase or decrease the AOA to maintain the lift necessary for the brace. I know what a wing stall feels like, because I've done it in an airplane. On the other hand, I can't prove that it was a stall because I didn't specifically measure airflow separation. On the other hand (that's three hands), the stall horn was blaring, the nose dropped, and it had all the symptoms of dramatic reduction in the lift-to-drag ratio. Same with a paddle brace (except the stall horn) I think most who have paddled with a Greenland paddle can feel the effect. If the angle of attack gets too high, the blade dramatically loses lift (thrust, or whatever the term should be in a kayak). That is why the stroke always morphs into one that keeps the blade flying. I will not insist that I keep the blade from stalling entirely during a forward stroke, because stalled wings do produce lift, but I am sure that I am keeping it from going too deeply into a stall, and possibly keep it out of stall for most of the stroke. The effect of stalling (or deep stall) for a forward stroke would be reduced efficiency, which is much more subtle than a failed brace. It took me a while to learn not to just yank the blade back through the water, and I'm not sure if I ever really mastered it to full efficiency (probably didn't) Have I proven that this is a stall? No, but it has all the same symptoms as a wing stall so I'm content assuming that it is one in the absence of conflicting information (which I am open to if shared). Steve Brown -----Original Message----- .... Do you have any tests that prove you can 1. detect stall and discern it from any other forces acting on the paddle and 2. Adjust the angle of attack rapidly enough to make a difference? By this I mean tests I can perform to verify or refute your claim. ..... 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/ ***************************************************************************
On 9 Sep 2004 at 18:00, Steve Brown wrote: > Many, if not all on this list can easily manipulate their paddle > during a sculling brace to prevent it from stalling. This is true if the paddle is fully submerged. If you're talking about a paddle blade on the surface, then the blade is planing and we're not dealing with lift. Increasing the "AoA" of a planing blade means that you're changing the ability to plane and the behavior is not the same as a stall. Mike *************************************************************************** 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 lift decently, but I have to admit I'm not quite sure about the mechanics behind planning at all. Steve Brown -----Original Message----- This is true if the paddle is fully submerged. If you're talking about a paddle blade on the surface, then the blade is planing and we're not dealing with lift. Increasing the "AoA" of a planing blade means that you're changing the ability to plane and the behavior is not the same as a stall. Mike *************************************************************************** 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/ ***************************************************************************
Steve wrote; SNIP Thanks for the discussion on stall but I already knew that. What I hoped to read was how you could prove you could detect and respond to stall in your paddle stroke. >I know what a wing stall feels like, because I've done it in an airplane. Does the magnitude of the effect help you in the airplane? I too have experienced it in an airplane and it was damned dramatic. Given the forces etc. on a paddle it doesn't sound equivalent. >I think most who have paddled with a Greenland paddle can feel the effect. >If the angle of attack gets too high, the blade dramatically loses lift >(thrust, or whatever the term should be in a kayak). Can most feel it? How do you know? Once you lose lift how do you separate the sensation of increased drag from the loss of lift particularly when you may have little or no decrease in boat speed? >That is why the stroke >always morphs into one that keeps the blade flying. Always? (See below) >I will not insist that I keep the blade from stalling entirely during a >forward stroke, because >stalled wings do produce lift, but I am sure that I am keeping it from >going >too deeply into a stall, and possibly keep it out of stall for most of the >stroke. The effect of stalling (or deep stall) for a forward stroke would >be reduced efficiency, which is much more subtle than a failed brace. It >took me a while to learn not to just yank the blade back through the water, >and I'm not sure if I ever really mastered it to full efficiency (probably >didn't) My point exactly but without the optimism. Keep in mind that paddlers using GP paddles and a drag oriented stroke can, at cruising speeds at least, keep up with other GP using paddlers supposedly using lift oriented strokes. How do you tell what part of the stroke is stall or lift if the resultant thrust remains the same or similar? >Have I proven that this is a stall? No, but it has all the same symptoms as >a wing stall so I'm content assuming that it is one in the absence of >conflicting information (which I am open to if shared). Most know that GP paddles can stall . I asked if you could prove that you could both recognize it during the stroke and make the appropriate adjustments to the angle of attack to stop the stall which hasn't been forthcoming. Your answer didn't help much. 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/ ***************************************************************************
Morning John, I'm claiming they're all lift oriented forward strokes, even with a euro blade. It's just that the shape of the euro blade delays stall at higher AOA and provides more lift at AOA beyond stall so they're not as fussy. Check out these wingtip vortices: http://www.geocities.com/jefferyjg/wake.html They are only created (in any size), by wings lifting at high AOA, such as during takeoff or steep turns. The little swirl paddler leave behind on either side of their boat (visible on a calm day) look suspiciously similar except rotated 90 degrees. By trial and error I learned which stroke gave the best pull with the GL paddle, same as I learned how to successfully do a sculling brace. After reading the sea kayaker article I mentioned a few posts ago, I learned the reason behind it. That article showed clearly how the shape of a euro paddle or especially a wing paddle helped keep water moving parallel to the blade face, but that with the Greenland paddle, the paddler had to supply the motion to do that. I'm definitely not saying that I was out paddling with my GL and paddle and suddenly realized my blade was stalling. What I am saying is that through trial and error I did learn how to generate the most pull (the feedback mechanism). Once this was learned, it became "automatic" and no longer required thought. Effectively, I had learned to continuously adjust AOA to avoid stall (or deep stall) without knowing it. I suppose the degree of success in doing this is at least one element that determines a person's forward stoke efficiency. Trying to explain, or prove how I did that is like trying to explain how I learned to catch a fly ball (usually). It is evident that I did, but explaining it with any accuracy would require a million lines of computer code. The reason for this example is not to imply that effective paddling is about the eye / hand / leg coordination required for catching a fly ball, but that the human brain is capable of solving very sophisticated problems which defy simple explanation or proof. Anyway, it seems like we are about 1" apart in our positions, but that we would each wear out our keyboards trying to close that gap - without success. One thing I am wondering, is whether the fussiness of the GL paddle (which we agree on) is integral to it's easiness on the body, or if it's the small submerged blade area during a cruising stroke, or both. I don't know if there are any extreme high aspect ratio paddles out there with curved asymmetrical blades? If so, it would be interesting to see if they retain the same benefits on the body for cruising, even though they would not retain the GL paddles benefits for sculling. Steve Brown -----Original Message----- ...... My point exactly but without the optimism. Keep in mind that paddlers using GP paddles and a drag oriented stroke can, at cruising speeds at least, keep up with other GP using paddlers supposedly using lift oriented strokes. How do you tell what part of the stroke is stall or lift if the resultant thrust remains the same or similar? ..... Most know that GP paddles can stall . I asked if you could prove that you could both recognize it during the stroke and make the appropriate adjustments to the angle of attack to stop the stall which hasn't been forthcoming. Your answer didn't help much. 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/ ***************************************************************************
Steve wrote; SNIP >Anyway, it seems like we are about 1" apart in our positions, but that we >would each wear out our keyboards trying to close that gap - without >success. That sometimes happens. >One thing I am wondering, is whether the fussiness of the GL paddle (which >we agree on) is integral to it's easiness on the body, or if it's the small >submerged blade area during a cruising stroke, or both. Maybe both. My own experience suggests that one can duplicate the feel of a GP paddle using a small area low aspect ratio paddle. Unfortunately, this also falls into the opinion category so I would never suggest that it actually happens only that it seemd to me that it did. >I don't know if there are any extreme high aspect ratio paddles out there >with curved asymmetrical blades? If so, it would be interesting to see if >they retain the same benefits on the body for cruising, even though they >would not retain the GL paddles benefits for sculling. I made one, tried it and it felt really strange unless I used the sprint racer's stroke. Didn't feel all that bad then but it did act strange in anything but a forward stroke. If I had spent mor time with it maybe I would have changed my mind but time was in short supply at the time. 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/ ***************************************************************************
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