Stern rudder in big waves

[josko]

I'm used to dropping in a high-angle neutral stern rudder when I pick up a wave. Works well for me and I like control that I get out of it.

Recently, though, I've been surfing bigger waves, and am having a hard time with blade stability in the water. Namely, when the kayak gets going, say >10 kts, the neutral blade (Ikelos) tents to flutter (shaft changes angle minutely clocwise or counter-clockwise) and all of a sudden develops a significant force either towards or away from the stern. It's almost as if the blade is stable at lower speeds, but tends to get unstable past 10 or so knots. Yanking the blade out of the water quickly is the only solution I have so far. I haven't dunked yet because of it, but came close.

So, the questions that come up are:

Has anybody else seen this transition from stable to unstable with a high-angle stern rudder in bigger waves?

If yes, what's the cure for it? (An obvious cure might be to reduce shaft angle, and get longflow instead of crossflow accross the blade, but that seems to take a lot of control nuances away for me.)

Is there an alternate approach (to a neutral stern rudder) for kayak surfing at higher speeds?

[JohnHuth]

I've had this happen to me too. I think that you are just making a transition into turbulent flow so a lot of force develops even at small attack angles - intrinsically unstable. I don't have any good solution except to enjoy the ride and get ready to brace when the kayak starts to yaw to one side.

I'd be interested in hearing if anyone has a solution.

[kate]

Offered without having any insight into the physics of the situation: what if you use a smaller blade? less force building up than with a big blade? let's hear it for surfing with greenland paddles....

[Phil Allen]

the kayak surfers (with specific surf kayaks) often use kids size whitewater blades. not sure if this might be a reason or not.

As to the cross versus longer direction flow, wouldn't you want it more towards the longer direction? Then with subtle changes of arm position you can transition between neutral rudder, stern pry and stern draw.

best

Phil

[josko]

Phil,

a low-angle rudder works for me if i plan to move it out to a stern pry, but for a stern draw, it moves my front arm out into an awkward position, plus I find it hard to generate a force (away from the stern) anyway near comparable to that achievable with a high angle/crossflow. I really like and appreciate the ability to generate a lot of force in either direction (towards or away from the stern) by just wrist control. The body and arms can stay put, thus allowing me to focus on edging.

If you've never tried a high-angle stern draw, you'll likely find it a go-to move in a range of surf conditions.

[JohnHuth]

A good stern draw is tough. I'm still trying to perfect mine. I try to keep my elbow at no greater an angle than 120 degrees and move it closer to my center of rotation. Don't over-extend the elbow as you put yourself at risk for a shoulder dislocation.

Try giving that a shot.

It's also the stern draw with an elbow angle of maybe 100 degrees in combination with boat lean - have you worked on that combination?

[josko]

John,

my key to the stern draw is to rotate WELL into it, in effect keeping both arms in front of the chest. Agree that a draw without rotation is an invitation to a dislocated shoulder.

[Phil Allen]

... I really like and appreciate the ability to generate a lot of force in either direction (towards or away from the stern) by just wrist control. The body and arms can stay put, thus allowing me to focus on edging.

If you've never tried a high-angle stern draw, you'll likely find it a go-to move in a range of surf conditions.

Hi Josko,

Maybe I'm missing something (this is the internet after all), but why use your wrists to change blade angle relative to the boat? Wouldn't rotating more or less transition you between draw, neutral and pry?

best

Phil

[josko]

I really like the degree of control I get by rotating my wrists. Also, using body rotation to set the paddle rudder angle would require me to rotate much more than I feel I need to with a vertical blade. To some extent, I may already be doing that, but wrists add a lot more control.

[Suz]

I really like the degree of control I get by rotating my wrists. Also, using body rotation to set the paddle rudder angle would require me to rotate much more than I feel I need to with a vertical blade. To some extent, I may already be doing that, but wrists add a lot more control.

Articulating the blade with your wrists (small tiny part of body that is relatively weak and susceptible to damage) is less efficient than articulating the blade with your body.

Try using your body with rotation and try anchoring the elbow closest to the blade in the water on your boat. A higher offside/dry hand will make the blade deeper in the water, a lower angle puts the blade closer to the stern. Play around and see how powerful it is.

Signed - she who avoids big waters nowadays so take with a grain of salt:)

Suz