RE: [Paddlewise] Why does rocker and carving work?

Scott wrote:

>However, if there is rocker, the power of the sweep
>stroke is pushing against only a couple of inches and
>it takes less force to move the bow on a pivot point
>back near the paddler.  Is this correct?

G'Day Scott,

Sounds as if your explanation of rocker is pretty much correct. I didn't
quite follow the carving (edging) explanation.

Looking at the hull of my boat, the bottom is long, straight, flat and
pointed at each end. The sides are highly curved so the shape of the boat
makes it look a vertical sheet near the bow and stern.

When the boat is upright its whole length is in contact with the water and
the bow and stern are acting like a fixed rudder. Thats one factor making
the boat go straight when its upright. Also imagine the boat broken up into
sections. Each section contributes to the effort needed to turn the boat, by
its depth in the water multiplied by its distance from somewhere near the
paddler. This sounds like your explanation also.

But! When you lean my boat on its side it is no longer floating on a flat
surface. The boat is now supported mostly near the middle rather than the
bow and stern ie the bow and stern are somewhat lifted out of the water and
don't contribute so much to drag at each end when trying to turn. Also the
rudder effect of bow and stern goes away because they act like a sheet lying
flat on the water.

I think this is also why it takes less effort to turn and steer boats in
choppy water, because it becomes possible to take advantage of turning
strokes when the stern and bow are out of the water.

Of course not all kayaks are designed like this, horses for courses! Mine is
optimised for paddling at sea without a rudder.

All the best, PeterO

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