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Question: Perfect Paddle Part Five :: Total Votes:7
Poll choices Votes Statistics
My paddle blades are rectangular 0  [0.00%]
Mine are oval or rounded a bit 2  [28.57%]
Mine are asymmetrical 5  [71.43%]
What's asymmetrical? 0  [0.00%]
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Topic: Perfect Paddle Part 5, what kinda shape you in?< Next Oldest | Next Newest >
Capn Jimbo Offline
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Posted: Aug. 15 2005,17:25



Ok campers today's subject is blade shape and something called Aspect Ratio.  Let's quickly cover the technical stuff.

"Aspect Ratio" refers to length divided by height.  A long narrow blade will have a higher AR than a short wide blade.  Keep in mind that Broze couldn't find much difference between blades that differed by 30% in area (ie a small area blade was about as effective as a large one).

Broze noted that one experimenter theorized that a long narrow blade would be more effective on the basis that the longer edge (longer perimeter) created more resistance and thus would be more effective. Broze tested this thoroughly by modifying blades to increase the the perimeter.  He tried wavy edges, sawtooth edges, square corners, even holes through the paddle - all in an attempt to increase the total amount of edge.  The result:

No difference.  The theory was bogus.  If longer narrower blades are more effective it's because they are longer, move faster through the water.  Remember that resistance increases as the square of the speed, so resistance (and effectiveness) increases.

Once again:  length (of paddle) is far more important than blade area (size) or narrowness/wideness .  A relatively small increase in length has a big effect on resistance.  Blade size (large or small) and narrowness (aspect ratio) make little difference .

Just two considerations:

1.  Narrow blades have less surface area so you must angle them more precisely (planing angle) when you do a bracing sweep.

2.  Extremely narrow or convex blades have a tendency to flutter.  This is not an issue with most blades.  Broze noted that narrow blades that are convex on both sides (to add strength) are subject to fast and uncontrollable "zigzag" flutter.  Beware of these!

How about assymetrical blades?

Now let's talk shape.  There are really two basic types: symmetrical and asymmetrical. See pic above. Symmetrical blades are rectangular or oval.  Asymmetrical blades look like the ends are cut off at an angle.  

Asymmetrical blades have one big but limited advantage: they are much less likely to twist if you are applying extreme power on entry.  This is of concern to racers, but Broze found that average paddlers will notice no difference.  However, since Broze found no negatives regarding asymmetricals, he recommends them.  Rounded end and also narrower paddles are also less likely to twist.

Bottom line:  A small-area, shorter asymmetrical or rounded blade will perform as well as a large, longer symmetrical blade.

:capn:

Next: flat, curved and spoon blades...


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Capn Jimbo

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Posted: Aug. 20 2005,16:21

What about a longer large area ASYMMETRICAL blade?  Or a short large area asymmetrical blade.  There are 27 possible arrangements of this experiment. Why only compare two.

And increasing perimeter doesn't necessarily increase surface area.  Perimeter like a sawtooth gives as much as it takes re: surface area.  And that's not counting turbulance.  Did he factor in that?

Just for us out here in the crowds, does Broze have any kind of degrees in engineering or physics?  His experiments aren't well-founded, his populations are often only one test subject and his results aren't supported by any statistical data.  He seems to be winging it on musings, incidental observations and poorly designed experiments that don't cover even the simplest variables.  I'm sure he means well and is a great kayaker but he isn't always doing good science when he searches for the answers.
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Tanner Offline
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Posted: Aug. 21 2005,16:21

OK, I'll just stick with my two paddles, "Back Death" and "Off-White, Less Intimidating Death" and go back to being blissful. :p

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reeln_skinny Offline
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Posted: Aug. 21 2005,20:13

Oh Crap!!!... Does this mean I cut the ends off my 2 best canoe paddles and wasted a can of bondo for nuthin??? :p

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Capn Jimbo Offline
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Posted: Aug. 22 2005,08:47

Regarding Don's, uh, observations

Broze says it best:  

Quote
"What matters most is how the paddle feels to the paddler.  In an attempt to discover or design the paddle that worked best for me, I experimented with many different paddles, and made numerous changes in the blades...what is most important to me is moving a fast sea kayak over long distances at near hull speed in all conditions.  My style of paddling and choice of paddles is intended to minimize wear and tear on my ligaments and joints (while achieving his goal).


That's good enough for me.  Matt Broze is a well respected, very experienced kayaker and not infrequent contributor to Sea Kayaker Magazine (which is as close to a bible or journal of our sport that exists).  Along with Chris Cunningham, Editor, these two fellows know their stuff.  They have forgotten more about kayaking and paddling than we will ever know.

From a perfectly scientific basis I'm sure we could come up with a million permutations or combinations of features that would no doubt require a supercomputer and a team of dedicated researchers who - with enough time and millions of dollars, I'd suspect - would come up with a scientifically impressive piece of... Crap.  Like a space shuttle with loose foam.

You get the idea.  Like Thomas Edison or our Eskimo forefathers successful kayak design has emerged not from scientific brute force, but from painstaking life experience and determination.  The Eskimo designed kayaks - using their own body to measure and rudimentary materials and tools - and based on experience and experimention over thousands of years.  Much of what they did could not and still cannot be scientifically quantified.  Yet their designs remain to this day as some of the best performing sea kayaks you can find, period.  Their hard won designs work and work very, very well.

Broze and Cunningham come from this tradition of dedication and blend as scientific an approach as is possible in what is still essentially an art. They tinker, experiment, theorize and try things in real world, on-the-water, trial and error.  Often they can't explain why something works, but they know it does.  They live and breathe kayaking.  None of us at this forum have the qualifications, experience or track record to really criticize their work.  To do so amounts to the kind of armchair "musings" criticized above.

Truth be told, the failings, if any are mine.  Broze could not possibly detail all his many experiments (which took years) in the limited space of a magazine article, but he did summarize them.  And in the interest of brevity I chose not to detail the all the details he DID provide; rather I further summarized his findings and included only enough detail to give a flavor of his work.  Didn't want anyone falling asleep.  Still I believe his impressive findings stand.

We would all be well advised to pay attention.

:capn:

And Don, regarding your criticism - yes, he did take into account that the sawtooth (and other) does not increase area - in fact, that was his objective - he wished to keep blade area the same to isolate the effect of differing perimeters (and types of perimeters).  For what it's worth, that is a typical scientific approach.  He found that perimeter alone had no significant effect.


Edited by Capn Jimbo on Aug. 22 2005,08:51

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Capn Jimbo

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Posted: Aug. 22 2005,16:12

Let me apologize about the perimeter experiment as it was not Broze who suggested perimeter would increase resistance. And I assumed he meant that it increased area.  However, it didn't require extensive experimentation to determine that.  

If, however, the original author meant that increased perimeter, area remaining the same, would increase turbulence then he may be correct and Broze wrong under lab conditions.  If the turbulence was significant enough it surely would increase resistance.  

I'm sure Broze or his counterparts never consulted a turbulence theory expert to best determine how to modify the paddles and the difference may have been too slight to detect with their modifications.  But I would be amazed if any current paddles have a significant difference in area: perimeter ratio.

And to a degree I will allow for some of the confusion perhaps being the result of Jimbo editing the post of a more convenient length.

But I do take exception to the inferred reference that hands-on knowledge is more accurate than and preferrable to applied science.  Hunches and backyard know-how would never have created a space shuttle.  And the science of kayaks has improved them and the manufacturers use science constantly in their design and production.

I am amazed that you would think a team of scientists would only come up with "crap!"  I am certain that the kayaks used in the Olympic races weren't slapped together in someone's backyard.

I don't believe that the eskimos made a better kayak BECAUSE they used body parts for measurements.  I believe they made great kayaks in spite of that fact.  How would a measuring tape or ruler possibly make their kayak's inferior?  They made their kayaks the way they did because that is all they had to work with.  And they are to be admired for how well they did.  But I would not agree that seal skin is a better hull material than Kevlar.

And to describe kayak design as an "art" instead of a "science" is of course nonsense.  We always try to get away with that cop-out when we don't understand all of the facts, but the America's Cup sailboats are not works of art by design.  No salty mentor without any degrees is going to look at the specs of the boat and, on intuition, over-ride the technical data and suggest that the length or beam of the boat be adjusted a "schosh," regardless of what Hollywood would have you believe.  

The only "art" in my QCC is the color selection.  John Winters is not an artist--he is an engineer and designer.

And I respect your information about the authors of this information.  There is probably more to this than I see in the posts and a link to the articles would be appreciated.  

But the editors of Backpacker magazine still thinks organic foods are better for you and Rodale Press, their publishers, support reflexology, crystal therapy and aromatherapy.  High tech stereophonic magazines' editors claim small stones with symbols carve on them and placed on top of the system's speakers will improve the fidelity of the music. Auto magazines claim to have tested and shown that magnets attached to the fuel lines of cars can improve gas mileage.  Heck, popular magazines have supported magnets as human therapy for pain and other ailments.  

These periodicals never have to go through the rigors of peer review and none of their experiments are ever subject to strict examination.  All science is.

I don't doubt that the people at Sea Kayaker magazine know more than I and the first thought that the best paddle is the one that works best for you is very good.

I am always bothered by the fact that scientists are almost always portrayed as mad or incompetent in the entertainment media.  They only make the news when they CAN'T explain something, never when they have the right answer.  Everything we have today--medicine, healthy foods, computers, flight, autos, fabrics, materials-kayaks--are in some way a product of science.

When I grew up becoming a scientist was one of the most noble professions one could enter.  Today, they are considered laughable "geeks" and education is a joke.  With a president who thinks "Intelligent Design" is science and stem cell research is bad, we are in trouble.  

Oh, boy.  Sorry, I got off on a Rant and shouldn't have posted it here.  But I am always looking to see science and the scientific method properly used.
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PALADIN Offline
Marlin




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Posted: Aug. 22 2005,16:42

can we paddle in red states better than blue states.... :p

(Capn's Note:  WWJP?)


Edited by Capn Jimbo on Aug. 22 2005,18:34

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PALADIN Offline
Marlin




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Posted: Aug. 23 2005,15:56

Quote
(Capn's Note:  WWJP?)

maybe he's up a creek w/o a padlle :cool:


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7 replies since Aug. 15 2005,17:25 < Next Oldest | Next Newest >

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