Re: [Paddlewise] chine and stability

Alex wrote:

> By that do you mean the flatter the peak the more "secondary stability"
> (not having the Pices curve handy at present)?
>
> I suppose one point to really emphasis to everyone is steepness (or not)
of
> curve, not total height that we're talking about.

Secondary stability has to do with both the range of stability (how far the
boat can heel before it reaches vanishing righting moment, the total area
under the righting moment or righting arm curve, the maximum righting
moment, the slope(s) of the curve and the location of the maximum righting
moment (or arm).

The greater the range of stability the more heel one can experience and
still have some righting force.
The greater the total area under the curve the greater the righting force
sensed over the full range of heel.
The higher the maximum righting moment (or arm) the greater the sensation of
righting force at that particular point.
The location of the maximum tells when (at what heel) you will feel that
maximum force.
The slope of the curve at any point tells how rapidly the righting force
changes with a change in heel.

If one paddles a number of boats and compares their curves and how the boats
feel then it becomes possible to look at a curve and get a mental picture of
its stability characteristics.

No one type of stability will suit all paddling needs or preferences
although (from my experience) a  large range of stability, a smooth
parabolic stability curve, with its maximum roughly at or just past the
angle that one can easily lean the body seems to appeal to most people.

Clearly because people differ, no one curve shape will fit all.

The thing that I find most objectionable (once again in my experience) has
to do with the sensation of rapidly changing stability revealed by steep
curve slopes on either side of the stability curve.

Cheers,

John Winters
Web site address http://home.ican.net/~735769



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