Please excuse me for not following every post on this so maybe I have missed something. Nevertheless I will try to add some clarification to the issue. Every post that I have read so seems to base conclusions on actual paddling. I would caution you not to draw to many conclusions about physics from this kind of experimentation or experience. There are simply too many variables. How do you know if your output is exactly the same, what about boat differences, emotional differences and maybe the people you are paddling with just aren't in a hurry (or are). This kind of "test" involves an almost infinite number of variables from which one hopes to draw a single conclusion. The physics are well known (in fluid dynamics circles anyway) - the biomechanics are less well understood. The one thing that researchers have found is that human perception does not win any awards for accuracy. Anyone intersted in this kind of thing can read the various books on psychokinetics. Very sobering to me after thinking for years how accurately I could assess a boats performance just by paddling it and the reason why I developed KAPER. One writer wrote: > The only thing I can think of is that boat speed through the water must >have something to do with it. When the boat speed is low and the paddler is >applying lots of effort, the higher aspect ration blade with more slippage >is not going to be as efficient. However, as boat speed increases to the >point where its closer to the paddle speed, slippage becomes less of a >factor -- or, at least, so I surmise. Going back to my other post, where I >talked about paddling into a steep wind, would this account for the high >stroke rate and not going anywhere? In drag mode slippage is a major factor in thrust production regardless of the boat speed. It is through slippage that you produce thrust. The more paddle velocity (or slippage) the greater the thrust. As I said before, "slippage" is an unfortunate word as it seems to have negative connotations regardless of cases. Sometimes slippage is positive and sometimes negative. In the case of paddles it is usually positive. In the case of the lift mode slippage is still essential to develop the angle of attack. The only time that I can think of where slippage is an absolute negative facor is when the paddle ventilates. Keep in mind that paddle blade efficiency has nothing to do with biomechanical efficiency. I believe this is what causes so much confusion for "real life" testing. A paddle with the greatest efficiency may not match the paddler's biomechanically efficient stroke and rate. When that happens we should not assume the paddle is "bad" but rather examine if the paddler/paddle combination does work. The same paddle for another person may be wonderful. Regarding padldling into the wind one has to be certain about what causes the lack of progress. Pitching is a huge robber of energy not to mention the windage of boat , paddler and paddle. Without knowing all the circumstances etc. one cannot know what to attribute a lack of progress to. I can think of one good example where the paddle cause a lack of headway in head winds. Suppose when paddling into a heavy head wind the windage etc. slows you to a crawl. Frustrated you add more power. If your paddle is too small then it might ventilate and the thrust diminishes accordingly. In this case the harder you work the worse off you are because the paddle simply ventilates more. Sorry if this is cryptic. Not enough time in the day to write more. 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/ ***************************************************************************
At 11:22 AM 7/24/02 -0400, John Winters wrote: >I can think of one good example where the paddle cause a lack of headway in >head winds. Suppose when paddling into a heavy head wind the windage etc. >slows you to a crawl. Frustrated you add more power. If your paddle is too >small then it might ventilate and the thrust diminishes accordingly. In this >case the harder you work the worse off you are because the paddle simply >ventilates more. OK, that make sense -- and I suppose a narrower paddle, regardless of aspect ratio, would be more prone to ventilation than a wider one, right? Thanks, John. Sorry I'm not a technical type. Sometimes this stuff has to be spelled out in big letters for me. -- Wes --------------------------------------------------------------------------- Wes Boyd's Kayak Place http://www2.dmci.net/wesboyd/kayak.htm Kayaks for Big Guys (And Gals) | Trip Reports | Places To Go | Boats & Gear --------------------------------------------------------------------------- *************************************************************************** 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 11:22 AM -0400 7/24/02, John Winters wrote: <snip> > > The only thing I can think of is that boat speed through the water must >>have something to do with it. When the boat speed is low and the paddler is >>applying lots of effort, the higher aspect ration blade with more slippage >>is not going to be as efficient. However, as boat speed increases to the >>point where its closer to the paddle speed, slippage becomes less of a >>factor -- or, at least, so I surmise. Going back to my other post, where I >>talked about paddling into a steep wind, would this account for the high >>stroke rate and not going anywhere? > >In drag mode slippage is a major factor in thrust production regardless of >the boat speed. It is through slippage that you produce thrust. The more >paddle velocity (or slippage) the greater the thrust. As I said before, >"slippage" is an unfortunate word as it seems to have negative connotations >regardless of cases. Sometimes slippage is positive and sometimes negative. >In the case of paddles it is usually positive. While I agree with what John is saying here it may leave the impression to some that a paddle that has more "slippage" than another is better. I don't think this is what John is saying, but it may read that way to some. While more "slippage" from a given paddle usually implies more power, a paddle that is inherently more "slippery" will not generate as much forward thrust for the amount of energy the paddler applies to the paddle. For every action there is an equal and opposite reaction. If you want to push your kayak forward (action) you must push something backwards (reaction). In this way momentum is conserved. A paddle creates the reaction by pushing water backwards. The harder you push the kayak forward, the faster you will need to push the water backwards so slippage will increase. Looking at it the other way around pushing water faster (more slippage) results in more power. However this only applies as long as the paddle and technique are the same in both cases. Momentum is created by accelerating a mass to a speed. You can increase the momentum by increasing either the mass moved or the speed at which it moves. Momentum is proportional to both mass and velocity (speed). So you can double the momentum by either doubling the mass or the speed. The more water you move the less velocity you need to apply to the water to get the same momentum. Therefore blade that move more mass of water will experience less "slippage". While it is quite possible to get the same amount of thrust out of a paddle that moves a little water as one that moves alot, that is not the end of the story. The motion the paddle applies to the water is wasted. It is necessary to move the water to move the kayak forward, but it would be nice to waste as little energy in stirring up the water as possible as this energy would be appreciated for moving the kayak. The amount of energy you add to the water, like momentum, is based on the mass and the velocity of the water. However, the energy is proportional to the mass times the velocity squared. So each time you double the mass the energy doubles and each time you double the velocity, the energy quadruples. This means that if you want to keep the energy applied to the water (and wasted) at a minimum, you will do best to keep the velocity of the water at a minimum. The velocity of the water is what we are calling "slippage". What all this means is that while slippage is an inevitable consequence of paddling a kayak, minimizing the slippage will save energy. There are various ways to do this, all involve maximizing the mass or volume of water you are applying power to. For example ventilation brings air into the water so part of your effort is involved in moving air that doesn't have much mass, and you don't have as much water to push against. Fully submerge your blade so that as much of the available area as possible is working for you. Don't splash. Throwing water through the air is letting a small mass move at high speed. It generates momentum, but wastes energy. One of the deceiving things about paddles is when they are working efficiently they feel harder to use than when they are not. A paddle that moves freely through the water will feel a lot more comfortable than one that grabs a large mass of water and doesn't give as easily. Unfortunately, for a given amount of effort, the harder one to pull will generally make the boat move farther and faster. There are good physiological reasons for having the paddle "give" but it is hard to quantify and the needs of each paddler will be different. -- Nick Schade Guillemot Kayaks 824 Thompson St Glastonbury, CT 06033 (860) 659-8847 *************************************************************************** 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/ ***************************************************************************
John, Matt and all. It seems to me that everyone ignores one thing when discussing this subject, and I'd like to hear what those with greater gray power than I have to say about it. All the discussions seem to assume that the power output is all going to drive the boat forward at a constant speed. However, the boat/paddler mass is alternately being accelerated by the paddle stroke and then decelerating between strokes. It seems that, given a large enough engine, a large-bite paddle can be pulled through the water quickly. But if power is limited, a smaller paddle allows higher reps, which minimizes the period of glide between strokes and therefore the subsequent loss of energy due to acceleration/deceleration. The closer together the strokes come, the less deceleration there is between strokes and (I assume) the more efficient the biomechanics / stroke / paddle combination becomes. 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? Quantitatively, how much difference does this pulse-drive factor make? Just wondering, Harold *************************************************************************** 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/ ***************************************************************************
Harold wrote: >>>>>All the discussions seem to assume that the power output is all going to drive the boat forward at a constant speed. However, the boat/paddler mass is alternately being accelerated by the paddle stroke and then decelerating between strokes. It seems that, given a large enough engine, a large-bite paddle can be pulled through the water quickly. But if power is limited, a smaller paddle allows higher reps, which minimizes the period of glide between strokes and therefore the subsequent loss of energy due to acceleration/deceleration. The closer together the strokes come, the less deceleration there is between strokes and (I assume) the more efficient the biomechanics / stroke / paddle combination becomes. 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? Quantitatively, how much difference does this pulse-drive factor make?<<<<<< I wrote the following for a Sea Kayaker article back in 1992 (Note: Since I copied this directly from my computer it is probably what I turned into Sea Kayaker---so after editing it may not have all gotten published and I'm too hurried to check just now)? "Reducing the swing weight of the paddle allows a faster transition between strokes. This reduces the amount the kayak must be accelerated during each stroke to recover the speed lost to friction during the interval between strokes. It takes more energy to accelerate a kayak than it does to maintain its speed because now inertia (as well as the already present forces of friction and wavemaking) must also be overcome. The frictional and wavemaking resistances (drag) also are higher with greater variations in speed. The energy savings from the time spent traveling at less than the average speed does not balance the extra energy used travelling at more than average speed. This is partly because frictional resistance increases at nearly the square of the speed. Also, when travelling at or accelerating to the speed where wavemaking resistance becomes a significant factor (around 4 knots for a typical sea kayak) resistance increases at near the fourth power in relation to the speed increase. A more even speed is consistent with the higher paddling cadence that less blade weight allows." Back to the present. A higher stroke rate for whatever reason (such as with using a shorter paddle) would have the same speed smoothing benefits. I don't think this accounts for the apparent problem I'm having with the different paddles since it appears from the data given us that each stroke moved the kayak roughly an equal distance through the water and the higher stoke rate therefore made for a directly proportional (to the stroke rate) increase in speed (with its even larger proportional increase in drag). I think that is a far larger discrepancy than can be accounted for by the above. Partially, well I'd agree with that but, but only a small part. Here is another interesting tidbit from that same article draft that I just discovered: "[John Winters reported (in CanoeSport Journal V3,#4 Winter 1990, with blades pulled straight back at 90 degrees) that his experiments have revealed that for a given blade area the narrower (higher aspect ratio) blade will have less slippage. He theorized that the narrow blade's greater perimeter for a given area means a longer turbulence (drag) creating blade edge." John, this appears to be just the opposite of what you wrote in a recent e-mail on Paddlewise. I am curious what it was that gave you reason to have changed your thinking on this (if in fact I have interpreted both items separated by a dozen years correctly). Matt Broze http://www.marinerkayaks.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 9:57 PM -0700 7/25/02, Matt Broze wrote: > > >Back to the present. A higher stroke rate for whatever reason (such as with >using a shorter paddle) would have the same speed smoothing benefits. I >don't think this accounts for the apparent problem I'm having with the >different paddles since it appears from the data given us that each stroke >moved the kayak roughly an equal distance through the water and the higher >stoke rate therefore made for a directly proportional (to the stroke rate) >increase in speed (with its even larger proportional increase in drag). I >think that is a far larger discrepancy than can be accounted for by the >above. Partially, well I'd agree with that but, but only a small part. It is not only the stroke rate itself that gives the smoothing benefit. It is the shorter "down-time" between strokes that typically comes with a higher stroke rate. Imagine two kayaks paddling side by side at the same speed. Guy A has his paddle in the water for 1 second and then out for one second, the Guy B is paddling with in the water for 2 seconds and out for 1. They both will decelerate similarly between strokes, but Guy B will not need to accelerate as much during the time his paddle in the water. As a result he won't need to apply as much force and his stroke will be more efficient. The goal should be to minimize the time your paddle is out of the water while maximizing the "duty-cycle" or the percentage of time the paddle is in the water relative to the full stroke time. A fast stroke rate can do this, but it may break down if your stroke technique gets sloppy. It is possible to have a very quick recovery while having a relatively slow stroke rate. It requires concentration to maintain good technique while trying to go fast. Taking time to work on really sound technique will have much more effect on your efficiency than any choice of paddle. -- Nick Schade Guillemot Kayaks 824 Thompson St Glastonbury, CT 06033 (860) 659-8847 *************************************************************************** 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/ ***************************************************************************
To All; As a physicist, I just can't resist staying out of this conversation stream any longer. There are just too many factors involved to clearly define speed using stroke rate. Chaos itself, at this level of physics can have a significant effect on speed. Each time the paddle enters the water it does so as a slightly different angle. There may be a small change in rotation of the wrist from stroke to stroke. The wind changes from moment to moment, current, even changes in water temperature and salinity as these factors will effect buoyancy. Just too complicated. Fun to discuss, but meaningless except under the most controlled conditions. Technique is key, but even the best technique delivered every time cannot guarantee the same speed through the water every time. Dave *************************************************************************** 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/ ***************************************************************************
"Misisco, David J" wrote: > > To All; > > As a physicist, I just can't resist staying out of this conversation stream any longer. There are just too many factors involved to clearly define speed using stroke rate. I think that the discussions have implied many more factors than just stroke rate. > Chaos itself, at this level of physics can have a significant effect on speed. Each time the paddle enters the water it does so as a >slightly different angle. There may be a small change in rotation of the wrist from stroke to stroke. The wind changes from moment to >moment, current, even changes in water temperature and salinity as these factors will effect buoyancy. I am sure there are many factors that aren't being covered here, but this is the place to bring them up. As the above points are difficult to quantify, probably no more than a mention is sufficient. >Just too complicated. Fun to discuss, but meaningless except under the most controlled conditions. surprises me that a physicist would say this, but it seems that the sciences always develop a pretense when the lay people invade their territory. >Technique is key, but even the best technique delivered every time cannot guarantee the same speed through the water every time. Technique is definitely one of the keys, perhaps equipment may have something to do with it, perhaps physique, etc. What seems to be a given is that there are some people out there that consistently paddle faster than others in diverse conditions. To some of us, the discovery of this extends the conversation from "fun, but meaningless" to something which may have application outside of :controlled conditions". BTW, John Winters as a naval architect is pretty well known for his experimentation in "controlled conditions", Matt Broze for his vast knowledge/personal experience, and both of them being able to communicate it lucidly. > -- gabriel l romeu ø http://studiofurniture.com ø ø http://journalphoto.org ø ø http://kayakoutfitting.org ø ø http://kayaknavigation.com ø *************************************************************************** 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 have skimmed many of the posts on this subject ... much of it has been conjecture. In the absence of decent data under controlled conditions, I suspect we are tilting at windmills. Fun, but not very meaningful. Fluids are tough to do decent measurements on, and the physics is tough. Fluid mechanics is a "young" science. Someone dinged scientific folks for asking for data gathered under controlled conditions -- well, data gathered where the (many) variables are minimized at least allows the differences in the paddles to show up against whatever noise there is in the system. Asking for such measurements is good science. Knocking people for gathering them is crummy polemics. I hope Winters can get his tank back up, and can gather some data. Then I could take that data into the field with me and see if it jives with my experience. Back to the lurk. BTW, paddled on the river for the first time since the mold got me last September. Not fixed, yet, but got some handle on this stuff. Weak as hell, but stronger. -- Dave Kruger Astoria, OR *************************************************************************** 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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