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Question: Perfect Paddle Part Three :: Total Votes:9
Poll choices Votes Statistics
Shorter (16-18 in) blade 6  [66.67%]
Longer (over 18 in) blade 2  [22.22%]
What's a blade? 1  [11.11%]
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Topic: Perfect Paddle Part 3, shorter - a better motion in the ocean..< Next Oldest | Next Newest >
Capn Jimbo Offline
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Posted: Aug. 11 2005,05:38

Note: if you do nothing else, vote.  The poll will be useful.

As you'll learn here, shorter really is better.  It's about your motion in the ocean.

First a bit more about paddle length.  This is also not quite so obvious, as there are two elements:  shaft length and blade length.  

Broze experimented with two paddles:  both had the same shaft length and same blade area - but one had a longer/narrower blade while the other had a shorter/wider blade.  Naturally the longer bladed paddle was longer overall.   He knew that the center of area of the longer, narrower blade would not be much farther out than that of the shorter/wider blade.  Thus Broze assumed that the longer/narrower blade would have several advantages:

1.  It would have the reach of a longer paddle
2.  It would have less wind resistance due to a smaller blade area
3.  It would have about the same gear ratio (force required) as the shorter/wider/larger blade (he assumed the center of area of the longer blade was not much farther out than the shorter/wider blade. It seemed to him a longer/narrower bladed paddle would have all the advantages.  

Not so!  

After much experimentation he discovered that only the wind resistance was marginally lower.  The longer/narrower blade actually took more effort.  Why?  Stick with this now.  Because the tip of the longer/narrower blade is further out, it has to move faster, and creates more resistance.

Quote
Note: Resistance increases by the square of the speed.  Double the speed and you quadruple the resistance (loss). The tip of the longer paddle has to cover more water, moves faster and thus - more effort.


Bottom line: the longer/narrower blade requires noticeably more effort.  Bad.

Broze points out that a longer paddle (or blade) actually increased effort and stress.  He then concluded that shorter blades and paddles have a number of advantages:

1.  They allow you to keep the overall length low while maintaining enough shaft length to clear the gunwales.
2.  This allows you to keep your forward stroke closer to the kayak, thus improving tracking.  You spend less time and effort correcting your track.
3.  They have less swing weight - paddling is faster and easier.  
4.  Because they are lighter you can react and brace faster.
5.  Shorter paddles are stiffer, transfer power quicker and more accurately.
6.  Shorter paddles are more manageable, offer more control.

This is not to say that longer paddles have no advantages.

1.  They can be kept at a lower angle in strong cross winds, catch less air; however, if the wind DOES catch the longer paddle, it will be much harder to control.
2.  Longer paddles provide more leverage on sweep (turning) strokes.  Still, it is not hard to shift your hands on a shorter paddle with the same advantage.
3.  A longer paddle technically has a better reach from a high wave peak; however with practice and timing, short and long blades both can perform well.
4.  A longer paddle allows a lower cadence - but this is only obvious at top speed; both short and long paddles cruise with similarly modest effort.  

Note:  Shorter paddles (and a more vertical style) are better at top speed, can be "swung" faster, more accurately, allow you to put more power into your stroke.

Bottom line:  overall the shorter paddle had all the important advantages.

:capn:

Next...grips and blade area (this one is surprising)


Edited by Capn Jimbo on Aug. 13 2005,04:07

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Posted: Aug. 20 2005,15:57

Okay, let me tackle this post.

The center of area of the longer paddle would be exactly half of the additional length.  If the paddle was four inches longer the center of area would be two inches farther out.  This would vary fractionally with the design of the paddle but not significantly to matter.

The quote on resistance squaring with the speed is technically correct from a physics point of view.  But who says we have to paddle the longer paddle faster?  We all know that the longer the paddle is in the water effectively pushing water, the more work it produces.  The longer, SLOWER stroke of the long paddle may produce exactly as much work as the shorter paddle.  The two blades are not required to paddle the same number of strokes per minute to produce the same amount of work.

The shorter paddle will NOT have the reach of a longer paddle.  However you might chose to extend your stroke on the short paddle would work just as well with the long paddle.

Keeping your paddle at a lower level would have little to do with wind resistance.  Since the wind speed at three inches above the water isn't significantly different than it is at three feet above the water where is the advantage of a lower paddle?  If it is out of the water it has the same wind resistance.  There is just as much air at the water's surface as there is higher up.

But, all in all, Greenland paddles aren't my thing.  I prefer a large-bladed medium length paddle like my Werner San Juan at 230 cm to move the larger kayaks I like to paddle.  They have the surface area to make effective changes in direction quickly because they put a lot of force, or "work" as a physicist would say, into a quick short stroke.  They also can get the kayak up and moving quickly and can keep up a good pace with a slower stroke than a paddle with a smaller blade face.

Those're my thoughts.
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Capn Jimbo Offline
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Posted: Aug. 22 2005,16:40

Quote
Don- "The quote on resistance squaring with the speed is technically correct from a physics point of view.  But who says we have to paddle the longer paddle faster?  We all know that the longer the paddle is in the water effectively pushing water, the more work it produces.  The longer, SLOWER stroke of the long paddle may produce exactly as much work as the shorter paddle.  The two blades are not required to paddle the same number of strokes per minute to produce the same amount of work."


This was not Broze's point.  What I attempted (perhaps unsuccessfully) to relate was that - at the same cadence - the longer/narrower paddle creates more resistance.  The speed to which he referred was the speed of the tip of the longer/narrower blade, which is faster as it cuts a longer arc at the same cadence.  This is true no matter what the cadence.  

Keep in mind that he applied these blades to the same shaft length.  His point was simply that - at the same cadence - the longer/narrower blade would ALWAYS require more force.

He then delineated the advantages of shorter blades and accordingly a shorter paddle.

Quote
Don - "Keeping your paddle at a lower level would have little to do with wind resistance. "


To the contrary, keeping your blade at a lower level has EVERYTHING to do with wind resistance - and the longer/narrower blade (and accordingly longer paddle length) allows you to paddle at a lower angle, closer to the water.

Author and master tourer Derek Hutchinson points out that wind and waves go together - the higher the wind, the higher the waves.  He notes that the waves, like any obstruction, breaks up/slows down the wind and creates wind eddies (which are quite naturally close to the water's surface).  He advises to be sure to keep you paddle low to avoid having a strong wind snatch it out of your hand.

Keeping your paddle low is even more important in crosswinds, as it exposes a MUCH lower profile than a high paddle (which is much more likely to get ripped away in a gust).

Shelley Johnson (Sea Kayaker's Handbook) advises to increase your cadence, transition quickly (keep a blade in the water) and to "keep your paddle angle low so there is less exposure to the wind". I won't quote him but John Robison (Sea Kayaking Illustrated) heartily agrees.

Last, most sailors (including myself) are well aware of the effect of waves and the water's speed-reducing surface effect on wind.  Pelican's take full advantage of this buffer zone (but not for the same reason).

Try this sometime:  head downwind and hold your paddle horizontally at deck level.  Then lift it over your head.  You'll catch a lot more wind.  Trust me, I've tried this.  The difference is amazing.

Quote
Don - "I prefer a large-bladed medium length paddle... They have the surface area to make effective changes in direction quickly because they put a lot of force, or "work" as a physicist would say, into a quick short stroke.  They also can get the kayak up and moving quickly."


Regarding blade area Broze is very clear that beyond a certain minimum reasonable area, increasing the blade area another 25-30% offers no significant advantage.   According to him a smaller-area blade (with a just a bit more acceleration) can produce the same force as a larger one- but with none of the larger's many disadvantages.  

This was certainly Broze's most impressive finding, which surprised even him.

Quote
Broze stated "The most surprising result of my subjective tests was that large differences in blade area made little differences in performance.  I had accepted the "common knowledge" that bigger blades gave a better grip on the water (and) a stronger brace..."
.

See Part Four for details.

:capn:


Edited by Capn Jimbo on Aug. 22 2005,20:26

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Posted: Aug. 22 2005,17:23

Let me modify my last response about blade faces and wind resistance.  First, you are right that at the surface the wind is slower than, say, at the height of our heads.  The energy lost pushing the water is subtracted from its speed.  

I'll buy that as it is true.  But in reality we all have to get our paddle blades down to the water level so we all deal with that factor.  But small blade face or large blade face, the side on the up stroke is catching the same wind near our heads or above.  I will grant you that a larger paddle face is more wind resistant but not that at heights one foot above the water surface it is the wind speed significantly lower.  

I think I'm inclined to agree that over my head would be worse than at my chest.  But am I sure or would this be just leverage.  Which is an issue to consider, also.

Question:  when he used the longer thinner blades against the shorter larger area blades using the same shaft length did he end up with paddles with the same OVERALL length?  This would work against the narrow longer blade as leverage becomes and issue.

And that "bit more acceleration" could quantitatively be a large expenditure of energy over a long trip.  

You made good points, Jimbo.  But if one can move a larger blade through the water as fast and as efficiently as a smaller blade, he will go faster and it will be proportional to the difference in the areas of the paddle faces--all things being equal.

But all things not being equal and the fact that as one approaches the hull speed of any kayak it becomes progressively harder to go faster, the advantages of the larger blade may be neutralized by the increased hull resistance of the kayak.

And actually this argues for the thinner blade as other factors may be more than the larger blades advantage.  

And we are talking science, not art.
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PALADIN Offline
Marlin




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Posted: Aug. 22 2005,18:44

Good points both... and Don your last statement
Quote
But all things not being equal and the fact that as one approaches the hull speed of any kayak it becomes progressively harder to go faster, the advantages of the larger blade may be neutralized by the increased hull resistance of the kayak.

And actually this argues for the thinner blade as other factors may be more than the larger blades advantage.  


Is what got me very interested in Greenland style Paddles and more specifically Aleut Paddles.
Aleut paddles are ideally suited for cruising. Aleut paddles have a central ridge which stiffens the blade while letting the rest of the blade be relatively thin to give the paddle an overall low weight.But the central ridge that runs down the length of the blade does more than give the paddle a combination of strength and light weight. The ridge also controls the flow of water over the face of the blade. The back of the blade (not the power face) is without the ridge and some are slightly convex. This arangement results in no flutter or zig zag and a crusing speed that can seem effortless..




Not for everyone but interesting non the less.


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