I've been told that it allows for more efficient use of both arms: the rationale I heard was that your arm on the grip does more work than your arm on the blade with a straight paddle and this is "evened out" with a bent-shaft paddle.

I've also been told that it moves the water more efficiently (though, assuming the same blade, I fail to understand the theory here.)

I'm neither a kinesiologist nor a physicist, so I'm not convinced about either of these answers. I find a bent-shaft paddle more comfortable, but I've always chalked that up to personal preference more than anything else.

Can anybody shed some light on this?

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With a straght shaft paddle, one of two strokes is common:

• you put the paddle in the water ahead of you sloped like this \ and don't get great efficiency on the first half of the stroke, because it's hard to pull something down when you're above it
• you skip that whole first half of the stroke and just put the paddle in vertically right next to you. Now you're paying the overhead cost of bringing the paddle forward again twice as often because your strokes are only half length.

The theory with bent shaft is you can still reach forward for a longer stroke, but the blade face will be vertical on entry, so you can just pull it toward yourself, and the whole thing will be more efficient.

Apparently I had the paddle backwards in my reasoning above. The theory is that the "in front of you" part of the stroke is weak, so by having the blade at an angle you can put it in the water not very far in front of you at all, and get a longer push part in the back half of the stroke (the stronger half) because the blade is not lifting up against the water.

I have enough trouble stowing flat paddles for portages, and don't really think that powering across the lake as fast is possible matters much on a multi-day / week trip, so I've never bothered with them. (I do feather my blades when paddling into the wind though.) But that's the theory.

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It seems like the bent shaft paddle would actually be more horizontal on entry whether you reached forward or not... (With action more reminiscent of a paddle wheel.) Unless you were to reach your arm on the grip out and keep your hand on the blade tucked near your body... Maybe I do actually do this exact motion and just don't realize it, or maybe I'm just having trouble visualizing this at the moment. –  Edward Thomson Mar 18 '12 at 1:36
You're right - I heard the stuff about the first half of the stroke not being as powerful, but imagined the paddle "backwards" from how they intend it to be used. –  Kate Gregory Mar 19 '12 at 0:32
Aha, that makes sense! –  Edward Thomson Mar 19 '12 at 14:53

The point of the bent shaft is to maximize the amount of stroke for which the paddle is vertical through the stroke.

Take a look at this video. The logic is explain in this video. He does a good job of visually showing why you might choose a bent shaft paddle. He also explains that it is not good for all types of canoeing.

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