"DSK" wrote in message
I'd say that either displacement or cubic capacity equals comfort.

Maxprop wrote:
As a rule, yes, but a hull of a given volume can reach a point beyond
which increasing displacement has a negative effect on comfort, not to
mention safety.

Agreed.

... An example of this was a Norsea 27 in which a middle age man set out
to circumnavigate some years ago. The boat has an unladen disp/length
ratio of nearly 450, and with stores, extra fuel, water, equipment, etc.
the boat was simply too heavy and performed horribly in beam seas, which
rolled her over several times before he turned tail and headed home.

THe problem is that he was at the margin... if you graphed motion &
stability against increasing displacement on a given hull volume, you'd go
from extremely bouncy (too bouyant) at the light extreme, to increasingly
comfortable, then back downhill again as the boat lost responsiveness &
stability (which is at least half due to bouyancy, let's not forget), then
back up again as the boat becomes a submarine... the smoothest ride is 40+
fathoms down!

LOL. Beneteau has, but does not distribute, graphic studies of net
displacement vs. stability for all of its boats built after the mid-90s.
Not sure if the French gov't. requires them or what, but I think they are
all just computer models depicting the safety margins of their boats. I've
seen the ones that apply to boats in the size range that interests me, and
frankly it's a bit scary. Bottom line: don't overload a 39' Beneteau. And
I'd suspect the same admonition might apply to similar boats, such as
Jeanneaus, DuFours, Catalinas, Hunters, etc.= the plastic fantastics. What
was interesting is that there seemed to be an over-center point, beyond
which the stability of the boat fell off precipitously. It was not a smooth
curve, rather it peaked, then plunged. I'm surprised that boat builders
don't publish a *do not exceed* load figure for each boat, even if they
don't want those graphs out and about.

... Displacement seems to offset cubic capacity somewhat, making really
voluminous but light boats uncomfortable and making voluminous and heavy
boats more comfortable.


Yep. Everything is a trade-off. That's why life is such a good metaphor
for sailing....

Aw, heck, I want it all, dammit. g

Max