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Hi Meg -- While SUP paddling past your outrigger this week, I heard you mention the word "whirlpool" in reference to paddling (you were teaching your crew). I looked down at my paddle and saw not just one but 3 whirlpools! Yikes! Are whirlpools good or bad? I was playing with seeing what I could do to eliminate them, but before I get too into it, I thought I'd check with you to see what's up with whirlpools.
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(Meg's response)"As for whirlpools, I need to look at this while I'm on a SUP board but here are some thoughts: The goal is to sink the paddle before you pull yourself to it. This is the catch phase of the stroke. If you begin the pull phase of the stroke before you have total catch/adhesion, air can catch behind the blade thereby causing slippage of the blade in the water and creating whirlpools.
Whirlpools are an indication of a less than perfect catch.
HOWEVER, other things do come in to play here - in particular speed of craft. Let's talk about race starts in an outrigger for a moment. When the boat is at a dead stop, well that's some low boat speed - none in fact. So when we go to do our race starts, we think of our first four paddle strokes as short and deep.
Because the speed of the boat is nil there is great, great resistance and our paddles cause big whirlpools. They have to slip through the water a bit. The paddles have to slip because we are not strong enough to propel a 400 pound boat PLUS six people forward without some slippage. As the boat speed starts to pick up, within the first ten strokes or so, we can now fully submerge our paddles and get full adhesion without slippage because the boat is up and running.
This is why it is important NOT to have a paddle that is too big. In a perfect world we would use a smaller paddle going upstream and a bigger one going downstream. Stand up paddle boards are SLOW and upstream there can be great resistance on top of that. So, you want a paddle that you can submerge and have a good clean catch with but that won't overpower you and cause you to paddle inefficiently. When I go out next time I will look to see if I have whirlpools while SUPing."
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Hey Meg! Marcy (Haight) Peterson here... looking for you on Facebook, but wasn't sure of an e-mail address, so I Googled you! How are you?? We are on the verge of becoming empty-nesters, so I am reaching out to friends near and far!
ReplyDeleteSend me an e-mail when you have time.... marcypeterson602@yahoo.com
Hi Meg, Great piece. I've done a bit of study on the physics of paddles, mostly kayak wing paddles but canoe conventional paddles too. I think we should be careful to make the distinction between whirlpools (ventilation or pulling air down into the water) and eddies (lift vortices or swirling water). Ventilation is always bad, and a sign of pulling at the catch too soon. Eddies are what we're trying to achieve, getting all our paddling energy deep down into the water to move ourselves FORWARD! A couple of places to check into:
ReplyDeletehttp://www.surfski.info/content/view/270/38/1/2/
http://www.phys.washington.edu/users/jeff/courses/ken_young_webs/208A/scull.lift.html
Paddling (all forms) is a sport that enhances both the body AND the mind! See you on the water!
Al Bowers