[Paddlewise] Kayak stability curves

I was challenged back channel about my statement that stability curves
in Sea Kayaker are confusing because they assume a lower center of
gravity than is realistic.

Sea Kayaker uses 10 inches above the lowest point of the seat.

I would have to admit that that measurement is, in fact, reasonable.
Personally, I am top heavy and heavier than their theoretical paddler,
but really their "standard" is defensible. The center of gravity of
people is actually quite variable, but Sea Kayaker is not out of line.
Females and small people have lower center of gravity and males and
tall people higher.

I think that the most important feature of stability curves is in
their value comparing one boat versus another. As long as you maintain
a consistent standard, this should work. The absolute value of the
righting moment is very variable depending the actual center of
gravity of the system and thus perhaps of less value.

If someone uses 11 or 12 inches for the height of the center of
gravity, the curves will look very different but the relative pattern
comparing one kayak with another is maintained.

Sea Kayaker has a web page that discusses the methodology of their
testing / calculations.

http://www.seakayakermag.com/PDFs/Kayak_Reviews_Info.pdf
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