Eddy lines, boils and rips

[lhunt]

I don't think it matters what you are racing, exit speed onto a long straight is critical. I suspect it was the different arcs around the buoy as opposed to the turning strokes, as such, that made the difference, since it allowed you to carry more speed.

...Mmm, maybe. I think that was sort of my point - a tighter arc saves distance but not necessarily time. (He may have also politely have swung a little wider to give me more room.)

The interesting question is how effective would a bow rudder have been compared to other techniques to create the arc you used. I suspect not as effective since it would inherently mean your paddle was not being used to keep speed up while stuck in the water as a rudder.

Yes, that's the best point. Any time I try to do a 180 deg. bow rudder conservatively, so as to save speed, it takes too long to get back to the forward stroke and defeats the purpose.

...I suspect how it is done has a huge influence as well as just how quickly you are trying to pivot the bow.

In this case, we were both using wing paddles. If you look at the video here: you see a degree of control that I have a hard time getting with the wing paddle. (Also, I count 10 seconds for the turn on the video, plus you would need more to get around the rest of the arc and back up to speed, so it doesn't seem to be all that fast). I see that some people on the web recommend a cross bow rudder when using a wing - maybe I'll try that some day.

As to the man I was racing with, I said we were evenly matched, but that isn't fair. I think his boat was less optimized for speed than mine, which would make him probably the stronger paddler.

[lhunt]

Lisa- a well executed bow rudder should not take away speed.

Maybe it matters how fast you are going to begin with (the sedate pace of the videos helps you see the action but I'm not sure it scales up). Also, even though the momentum changes slowly, it does change. These guys are all almost at a standstill at the end of the process, and there is still some turning to do.

As Doug says, you can get back up to speed in 3 or 4 strokes, but that's a high cost in a close race.

I'll play with it some more this summer. New skills are a blast, anyway!

Lisa

[EEL]

...Mmm, maybe. I think that was sort of my point

Indeed. I was agreeing with you. Corners require a interesting balancing act between minimizing time spent in them and maximizing speed out of them.

If you look at the video here: you see a degree of control that I have a hard time getting with the wing paddle.

It sure looks to me as if there is a goodly amount of speed bled off in that video although he appears to be making a fairly tight turn compared to the Boston Bob video. No free lunch.

Ed Lawson

[Pintail]

Phil, I have to say that I think you are wrong (sorry, mate!) The video of BobB turning shows <me> two things: (i)there is plenty of speed loss in his turn and (ii)his paddle blade held amidships signifies not a "bow rudder" to my thinking, but a high-braced turn, almost...

"Bow rudder" means (to me) <at the bows> -- how else should it be interpreted? A good bow rudder usually involves some leaning forwards on the part of the paddler and a stretch towards the toes -- and unless there is speed degradation, I suspect that a bow drawstroke is being used. OK, you may then ask "what is the difference between bow rudder and bow draw stroke?" and the answer is "very little!" All strokes sooner or later become one and the same thing -- to a degree (well, don't they?): one on the left and one on the right, as some very wise person once told me.

Good bow ruddering technique involves a slow and progressive opening of the blade face -- therein lies the cause of the inevitable speed degradation.

[Phil Allen]

We should probably make this a different thread, but Lisa's real question is how to change direction with the maximum possible speed in the opposite direction. The bow rudder(draw/pry) doesn't involve active paddling, so I think it's likely not to be the racer's answer unless you have lots of room and can mix it up with forward strokes to keep speed up. Tight turns require a zero velocity at some point, so getting speed up in the opposite direction will likely require extra effort no matter what.

Phil

[tyson]

One strategy is to sweep, bow rudder, sweep, bow rudder... with a good strong edge to the boat.

[leong]

Lisa- a well executed bow rudder should not take away speed. Just like with the rudder (boat or paddle) at the stern, it only works when water is flowing smoothly over the blade. Many paddlers just stick it out there like a pole in the water to pivot around, which will rapidly kill all speed.

Phil

Hmm. There's no free lunch. It has to take away speed, although you can do it efficiently, or not. If there is no retarding force then there is no turning force. For simplicity, consider a flat plate rudder (or paddle or whatever) just held in place. Denote ang as the angle of the rudder. The maximum side force (the force that turns the kayak) occurs when ang = 45 degrees. At this 45-degree rudder angle the side force of the rudder is equal to the retarding force of the rudder. In this simple case of a flat plate rudder, the retarding force is proportional to the product sin(ang)*sin(ang). The side force is proportional to the product of the sin(ang)*cos(ang). It’s much more complicated with a curved rudder, wing paddle, etc., but there’s still no free lunch.