Why does a Kayak turn?

[cfolster]

More specifically, why does it turn right on a left edge and left on a right edge.  Perhaps everyone understands this, but I don't understand the physics behind this.

i understand you're causing a shorter profile, and that profile is curved, but I can't make the connection from there.

Can someone enlighten me?

[cfolster]

Been continuing to think about this and wondering if it's more about what your body is doing than the boat profile presented to the water.  Maybe combo of both. 

[billvoss]

Especially in a hard-chine kayak like I paddle Cathy, if you temporarily create a curved keel your path will curve.

Quote

Paddlers do leaned turns by leaning the boat outward on a turn. To turn right, lean left. The opposite from how you lean a bicycle. When upright, the keel of a kayak tends to keep it going straight. Lean a hard-chine kayak over far enough, and the chine will start to function as a keel. However, since the chine is curved, the boat starts to carve a turn. You get some benefit from leaning a multi-chine kayak while turning. In a hard-chine boat this effect is more pronounced and felt at a lower angle of heel (in other words, even when leaning less) than in a multi-chine boat.

From: https://www.pygmyboats.com/hard-chine-vs-multi-chine.html

A good page for background describing with pictures the difference between hard-chine and soft-chine among many other kayak traits is http://topkayaker.net/Articles/Instruction/HullDesign.htm

P.S.  If you build a kayak with an actual curved keel, the kayak will always want to turn in one direction when you are not leaning.

[cfolster]

I think I have the answer to my own question:

I think if I picture the curve that is presented to the water, it's not straight up and down in the water (like a keel is), but on its side a bit.  A curved edge, propelled forwards, is going to move in the direction of the front of the curve, which is opposite of the way you're edging.  If you were to edge on that same side and paddle backwards, the back of the boat would go in a direction opposite the edge.

If there was absolutely no force exerted on the boat by propulsion wind or wave, and you could edge at the exact center of a symmetrical curve (only exists on sterling kayaks to my knowledge and still not possible because we're human), the boat would not move.

ps does anyone else make a Kayak that's symmetrical front to back?

[scamlin]

Cathy:

Your summary is the normal explanation and one I've offered many times.

I do, however, remember a British coach on Peaks Island many years ago suggesting it was more complicated: the shorter water length of a edged boat definitely makes it easier to turn--so the force of the sweep stroke on the outside of the turn would have a turning effect regardless of the direction of the edging.  He had us try it both ways: a sweep stroke with edging on both sides.   I remember the results were ambiguous: while it felt more awkward to edge towards the turn while sweeping on the other side, the boat still turned almost as well.   On the other hand, many of us unconsciously and seamlessly make course corrections under way by edging in the conventional way to avoid corrective sweep strokes.

So which is the bigger factor: edging or the short water line?   I still edge on the outside, but concluded that it's more complicated than the conventional explanation--like much about kayaks moving through water.

Cheers,

Scott

[Phil Allen]

on the point of making it easier to turn, edging also alters the boats relation to the front wave and releases the rear.  With the "correct" edge, the stern can smear across the water, while with the "incorrect" edge its more likely to knife in.  And yes the spreading peanut butter analogy is strong this morning.  As for the front, I need to think about it more, but it would seem that edging would have the front wave put more force on the boat on the side away from the turn.

Phil