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PostPosted: September 24th, 2005, 7:04 am 
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frozentripper qiuoted from the WCHA web site the following:
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The wider blade is said to have a larger surface area. During the paddle drive the blade is square and the water is hopefully locked to the power face. This water wants to move sideways off the blade when pressure is applied to the stroke. The wider the blade, the more pressure at the edge of the blade requiring more effort to square which contributes to produce that dull ache in your neck and shoulders


This includes some stuff that has always puzzled me. What, for instance is a "wider" blade. Maybe some one here knows the answer or at least knows when a bade becomes wide versus narrow. .

Another question I have is how often does anyone get the blade square to the flow? Seems to me there is only one "square" and an infinite number of "not square" angles. The comment that "the water is hopefully locked to the power face" really puzlles me. I have never heard of such a thing and my understanding of fluid dynamics is that a fluid will not support shear forces and so cannot become "locked" to a moving surface (Excluding, of course, the one surface adjacent layer of molecules in the boundary layer) . Does anyone know where this comes from and who determined it?

How did the writer determine that it was the wide blade and not the blade's area or its coefficient of drag that contributed to the dull ache and why is it essential to try to hold the blade square? I also wonder if there is some rule that says a wide (or wider) blade must have more area than any other blade.

Thanks to frozentripper for digging this up. I had heard these comments but did not know they were published anywhere

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PostPosted: September 24th, 2005, 7:42 am 
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I think most people consider any blade 8 inches or more as wide. I consider anything 6 inches or under as narrow. I didn't get through high school physics, so I tend to disregard the science, etc. However, I do log around a thousand k of paddling each summer, and I have developed some interesting opinions. I have struggled with bicep tendonitis for the last four years, and I have played with all kinds of paddles in an attempt to aleviate the condition. I stopped using the square 8 inch blade two years ago and switched to a 6 1/2 inch beaver tail. This didn't change much, although making those single-piece beavertails was fun. Well, this summer I made a very intertesting discovery. My new canoe is quite a bit higher off the water than my swift designs (no offence intended John). My entire body position in relation to the water has changed, and I'm pushing an 8 inch blade again with no pain. So I suspect that my previous discomforts were not caused by the blade width, but by an improper sizing estimate of the shaft. I always lowered the seats on the Winisk and Quetico about six inches down, so I think the standard mystical formulas for determining shaft length were not valid, if they ever were.

In any case, if someone is experiencing a great deal of discomfort paddling, i would look to form and placement before blade width. And keep in mind that if you are paddling 8 hour days, no matter what type of paddle you are using, at some point you will experience the pleasure of suffering.....not to drag this on forever, but last weekend I took 20 kids on an overnighter. We ported right off the bus and then had canoe exercises and then paddled about 12 k to the campsite. Anyway, sitting around the fire that night, one of the kids says "Geez, for some reason my back hurts". I cracked up...never having done anything physical before, he couldn't make the link between the exercise and the pain.............I stay in pretty good condition, but at the beginning of each summer, I do my share of suffering too as underused muscles step up to the plate.......if you are only doing one trip a summer, and that constitutes the majority of your paddling for the year, pain is probably going to be a reality, no matter how wide your blade.


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PostPosted: September 24th, 2005, 9:07 am 
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There's one little tidbit of info I'd meant to pass on sooner but forgot-

I've done a lot of photography both still and video of paddling. Some of the still images are action shots using high shutter speed to freeze action and I've used slow motion or frame by frame video as a teaching tool for paddle instruction. What I have seen on a number of occassions is quite a bit of flex in a paddle shaft. When the paddlers see how much the shaft flexed, they are generally surprised - had no idea the paddle shaft bent that much while using it. You'd need a large tank to test this, but I've always been of the opinion that the assumptions people make by doing a flex text of a paddle on dry land don't translate to what happens on the water. You can't see what the blade is doing in the photos mentioned above, but I'm pretty sure that it won't be flexing as much as it would on a dry land test where you're only putting force on the tip.

Any thoughts on that JohnW?


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PostPosted: September 26th, 2005, 6:44 am 
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Rolph wrote:
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You can't see what the blade is doing in the photos mentioned above, but I'm pretty sure that it won't be flexing as much as it would on a dry land test where you're only putting force on the tip.


Rolph makes a good point in that it is very difficult to know what the paddle is doing when paddling because you don't have a solid frame of reference plus there is some distortion by hte water. Using video is a good technique for finding out what happens to the shaft.

To do a proper job of measuring shaft flex you need to do a couple of things. First, you must apply the loads at the proper points. By that, I mean at the grip, the location of the lower hand and the center of effort. You can determine the center of effort (The point about which all forces are focused) by using standard fluid dynamics formulas or just calculate the geometric center and ignore the variation in drag coefficient across the blade length if the camber is fairly consistent. Secondly, You need to record the flex as X" per unit of length. In others words, divide the flex by the length between the grip and the support at the CE. failure to do this can result in confusing results.

The nice thing about this is that you don't need a tank.

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PostPosted: September 26th, 2005, 7:00 am 
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Rhaslam wrote:

Quote:
think most people consider any blade 8 inches or more as wide. I consider anything 6 inches or under as narrow.


I have heard many people say this but the problems are fairly obvious. For example, is a blade that is 8" wide at the top and tapers to 4" at the bottom a wide blade? Is a blade that is 6" wide along its entire length a narrow blade? Is an 8" blade that is 24" long wide and while a 6" blade that is 12" long is narrow.?

To provide another perspective on this, is a canoe that is 4' wide and 12' long a wide canoe and if so is a canoe that is 4' wide and 26' long also a wide canoe? Most people would recognise that "wide" in this context is relative to length.

Anyway, RHaslam makes a good point regarding paddling related physical problems. You cannot assume that one thing causes the problems. There are many factors and this is why I find advertising that claims a specific paddle shape or type will cure your ills. One can conclude from experience that X will cure your problem but that doesn't mean that X will cure everyone's problems. The objective of the testing is to determine in an objective manner just what kind of effect each characteristic will have and to what degree. Until someone does that the whole business is pretty airy-fairy.

Worst of all one might end up buying a lot of paddles and discovering that none actually help over the long haul.

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PostPosted: September 26th, 2005, 12:27 pm 
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Jwinters wrote:
The nice thing about this is that you don't need a tank.

I'm working on a video project about paddling right now. There's a pool in the backyard that I've been using for some of the content, I've been getting underwater shots by placing my video camera inside a fish aquarium with diving weights to keep it low and that's working quite well. I handn't planned on doing analysis of flex in power strokes, but it won't be much trouble to add that to the shot list. Might be fun. Doing this would be much easier than the math, a subject I was never fond of in school :).

PS John, Rolf is spelled with an F, not PH. Both my first and last names are often mispronounced or spelled, so I don't get cranky about it. Just don't call me late for the canoe trip, er supper or something...!


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PostPosted: September 27th, 2005, 12:17 am 
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I don't know exactly how you set it up, but here's a caution about apparent paddle flex from videos, and even stills. I took some stills and videos with my digital still/video camera from a moving vehicle, perpendicular to the direction of travel (out the side window). When I played back the shots, I noticed something funny.

While objects in the distance were properly rendered, vertical elements in the foreground were not. For instance, those concrete barriers along roadsides. The vertical cracks between them showed up slanted far from vertical on the images. And vehicles passing in the opposite direction were "squashed" like trapezoids. I believe this is from the sensor being scanned while the item moves across the sensor. This would not happen with analog photography, and I suspect it would also happen with non-digital video. Something to watch out for, that may exaggerate paddle flex.

How do you operate the camera in the fish tank? My camera has a remote control that might be handy for that.

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PostPosted: September 27th, 2005, 4:18 am 
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Good observations about movement and video SGrant. About the only thing I'd be able to prove to my satisfaction is whether or not blade flex under water is similar to the flex it exhibits if you touch the tip on the ground and flex it out of the water. You'd need a high speed camera set up to do any quantative analysis. Video is normally shot at 24 frames a second which is fast enough to fool our eyes into thinking that 24 still frames are actually fluid movement when shown in a sequenece. When shooting something that's moving fast and playing back frame by frame later, you can see how the camera is building the image from top to bottom though I believe it actually starts at the bottom (the lens inverts the image, which then gets translated through the electronics). If your camera has a "shutter speed" function, you can use that to get rid of some/most of that distortion caused by movement. The camera I'm using is a Canon XL 1 which has good lenses, good imaging device and a good high speed shutter function.

The top is open on the fish tank. I leave 1/3 of it above water and the camera is in the bottom third under water. I simply lean over top of the tank and operate the controls by reaching into the tank. My view finder swivels up enough that I can look into it. The first time I tried this was with a betacam worth about $60,000 - that was nerve wracking. My little XL 1 is almost a disposable camera by comparison, but since I had no trouble before I suspect all will be well this time too.


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PostPosted: September 27th, 2005, 6:19 am 
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Rolf wrote: (See, I can get it right) :D

Quote:
PS John, Rolf is spelled with an F, not PH. Both my first and last names are often mispronounced or spelled, so I don't get cranky about it. Just don't call me late for the canoe trip, er supper or something...!


Sorry about that. I used to padle with a guy named Ralph. He must have made a bigger impression on me than I thought. He baked a fine bannock.

Regarding your video you might give the canoe club at Mississauga a call. I think they havea paddling tank for training. It may havea glass viewing port. Another possibiliy is to use a swimming pool. Most of the Olympic type pools have viewing ports under water to analyse swimming strokes.

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