Hydrodynamics of draw strokes

[JohnHuth]

I'm teaching a course in the fall called Primitive Navigation. One item I'm working on is the principle of lift in sails. One gets a similar phenomenon in a hanging draw and a cross draw. The "lift" in the draw helps you turn or move sideways. The same principle applies to a stern rudder.

At some point, I'd like to get some help with with a volunteer to do a hanging draw while I photograph it, or to have someone photograph me.

(or, if someone has a good photo, even better)

The main thing is to have a clear day, low wind, and a dark bottom. I suppose as an added benefit, I can explain all the stuff about vortices, turbulence and the like to someone who can help out.

Thanks in advance!

[Doug]

I'm teaching a course in the fall called Primitive Navigation. One item I'm working on is the principle of lift in sails. One gets a similar phenomenon in a hanging draw and a cross draw. The "lift" in the draw helps you turn or move sideways. The same principle applies to a stern rudder.

At some point, I'd like to get some help with with a volunteer to do a hanging draw while I photograph it, or to have someone photograph me.

(or, if someone has a good photo, even better)

The main thing is to have a clear day, low wind, and a dark bottom. I suppose as an added benefit, I can explain all the stuff about vortices, turbulence and the like to someone who can help out.

Thanks in advance!

John,

I'd be happy to photograph you for this project and others you may be interested in. Please IM me and we can work things out.

Doug

[brambor]

Same here. I would photograph you. Send me a PM if interested.

John,

I'd be happy to photograph you for this project and others you may be interested in. Please IM me and we can work things out.

Doug

[djlewis]

A few videos here... http://bit.ly/9CEB6P. None of these, however, shows good vertical paddle style that I was taught is important to the stroke's efficiency. But they do get nice sideways motion.

--David.

[JohnHuth]

David -

Thanks. I need a real sharp close up though, to see the vortex shedding on the trailing of the blade. That would also require a nearly vertical angle of the shaft and a very modest attack angle of the blade - so the positioning you mention definitely helps illustrate the hydrodynamics.

Extra points for the initial vortex on the leading edge of the blade!

I'll be in touch with the posters - I may need two people to get a decent photo - perhaps using a canoe as the photo platform. One person paddles and the other takes the shot.

[Phil Allen]

John- What about taping a thin long piece of mylar or other light weight material (xmas tinsel?) to the blade to illustrate what's happening with the water? That's what they use on sailoats to figure out what's happening to the wind at the trailing edge of a sail.

Phil

[rick stoehrer]

John- What about taping a thin long piece of mylar or other light weight material (xmas tinsel?) to the blade to illustrate what's happening with the water? That's what they use on sailoats to figure out what's happening to the wind at the trailing edge of a sail.

Phil

that's a very cool idea phil.

i spray painted the 2 blade sides of an old paddle fluoro orange and the other fluoro green to use as a tool while explaining blade angles and such. sometimes it's hard to see the faces black paddle in the water...you may find something like that useful for the color contrast as well.

[tyson]

I need a real sharp close up though, to see the vortex shedding on the trailing of the blade.

With that sort of a closeup, does it really need to be done in motion? How about finding a bit of flat water with current next to a rock or dock? That would really let you setup and control the shot. ...and then combine that with shots showing more context that are taken in boats.

[brambor]

Now now now where is the adventure in that ?

:D

With that sort of a closeup, does it really need to be done in motion? How about finding a bit of flat water with current next to a rock or dock? That would really let you setup and control the shot. ...and then combine that with shots showing more context that are taken in boats.

[djlewis]

David -

Thanks. I need a real sharp close up though, to see the vortex shedding on the trailing of the blade. That would also require a nearly vertical angle of the shaft and a very modest attack angle of the blade - so the positioning you mention definitely helps illustrate the hydrodynamics.

Extra points for the initial vortex on the leading edge of the blade!

Oh, you want close-ups of the blade/water dynamics.

Why mess with a moving boat -- no, two moving, synchronized boats! -- and all the complications that involves. Find some moving water by a steep shoreline, rock or such. Stick the blade in and aim the camera at it. Nice and simple.

Or, if you can't find the right juxtaposition of moving water and stable platform for "paddler" and photographer, how about putting a tow line on a boat, anchor to something stable on shore, and work from the -- hopefully stable -- boat.

--David

[gyork]

Oh, you want close-ups of the blade/water dynamics.

Why mess with a moving boat --

--David

Not sure of the quality of the video, but many of the waterproof (underwater) cameras allow for video clips. Might suffice to exhibit the action of the telltales or whatever (pool session?).