JimC wrote:
stability analysis of the 26M/X. It certainly has a high center of
gravity, and the metacentric height has to be pretty low.

It operates on the same principle (ballast carried within the the hull,
in the lower portion of the hull) as most ocean-going vessels.

Yes, and more than a few modern vessels have rolled over. Keeping
track of weight distribution is one of the primary jobs if the first
officer on most ships. Using phrases like "operates on the same
principle" is like saying it "obeys the laws of physics." It was wise
of you to avoid those boats that don't obey the laws of physics.

When you look at the long list of warnings, such as:

NO MORE THAN 6 PERSONS, 960 POUNDS.

WHEN POWERING OVER 6 MILES PER HOUR:
- NO ONE ON THE CABIN TOP OR FOREDECK.

and

NEVER POWER THE BOAT OVER 6 MILES PER HOUR WITH THE SAILS UP.
The result could be instant capsize.

its clear that there are issues here. And I should add, the my real
point here is that these issues simply do not exist on "normal" boats.

And of course, we don't want to even consider the issues if the
ballast tank is empty.

In the past you've poo-poo'd these warnings as just "lawyer talk," but
I hope now that you've had the boat for a while you take them more
seriously.

And the
same principle used in tall ships for hundreds of years.

I really don't think you want to use the stability qualities of
traditional ships as an example. And remember, even they used ballast
with a specific gravity somewhat greater than one.



And the other issue is that the water ballast extends all the way from
stem to stern. This can't be helping the pitching moment at all.

Wrong again. it extends about 2/3rds, and the front and rear portions of
the tank taper to sharp end portions and are therefore of little mass
and no real consequence re the distribution of mass.

Not according to the published diagram:
http://www.macgregor26.com/drawings/drawings.htm

Its pretty clear from this that the ballast extends all the way
forward, and that in fact a substantial amount is forward of the mast.
You should really spend some time learning about your boat, Jim.