On 6/21/04 1:51 PM, in article , "Michael
Daly" wrote:

On 18-Jun-2004, Wright wrote:

Given two identical
touring kayaks and two people of equal abilities, if one weighs 125 lbs and
the other weighs 190 lbs what would be the differences, if any, on stability
and performance?

If you made it through the nonsense that followed, Brian's answer is correct.
Low-placed weight increases stability, high-placed weight decreases it. Hence
women and shorter men tend to see more stability than tall, big people.
Adding
weight (gear) up to a reasonable load limit tends to increase stability.

If you pick up a copy of Sea Kayaker magazine, you'll find that they include
a graph of stability (righting moment vs angle of heel) with every review of
kayaks. I recently posted about this and can add that they plot four curves.
There are curves for light and heavy paddlers both with and without gear.
A light paddler with gear always shows the greatest stability, while the
heavy paddler without gear always shows the least stability.

Mike
Thanks for the reply. It certainly makes sense that more gear weight (up to
a point) low in the boat would make it more stable. The heavy keel on a
sailboat would be an extreme example of that. Here is the part I don't quite
follow. I have seen the reviews in Sea Kayaker magazine and they assume, if
I am understanding them correctly, that the center of gravity for both the
lighter and the heavier paddler is 10 inches from the low point of the seat.
In other words the center of gravity is at exactly the same place for both
paddlers (without any gear). Yet the curve for the lighter paddler
indicates more stability. Is this because weight below the center of
gravity and weight above the center of gravity are not created equal? That
is, the 50% of the weight of the heavier paddler that is above the center of
gravity must cause somewhat more instability than the 50% of the weight of
the lighter paddler? Is that correct, or am I misreading the graphs?
Chuck

On 21-Jun-2004, Wright wrote:

I have seen the reviews in Sea Kayaker magazine and they assume, if
I am understanding them correctly, that the center of gravity for both the
lighter and the heavier paddler is 10 inches from the low point of the seat.
In other words the center of gravity is at exactly the same place for both
paddlers (without any gear). Yet the curve for the lighter paddler
indicates more stability.

Interesting - I never noticed that comment about CG position in the reviews.
Since these are static and not dynamic stability calculations, the mass at
the CG is all that matters. If both the heavy and light paddlers have their
mass at the same point, then the only difference is the quantity and the
stability curves do not reflect the difference in distribution.

Since that CG (10" up and 10" forward) is above the center of bouyancy, any
heeling will have it contribute to the overturning moment. The heavier
paddler will still have the lesser stability at a given angle of heel. If
the CG was determined for real paddlers, taking into account different CG
positions, the moments calculated would be slightly different.

Don't forget that these figures still ignore the fact that a real paddler
will tend to keep his/her body roughly vertical if the kayak heels. This
greatly changes the overturning moments.

Mike