Courtney Thomas wrote:
Is there any way to determine 'real' displacement as a practical matter
for a typical sailor, other than loading the boat per it's intended use,
and seeing what happens ? :-)

Sure. A lot of Travel-Lifts have scales built in. Just have one of them
hoist your boat.



For is it not typically the case that... someone buys a boat, is
uncertain as to what and how much loading will then ensue, but then sets
about their sailing regime...


That's pretty much it, and of course people raise their waterlines all
the time...


This might seem to indicate that...the safe thing to do is to buy heavy
displacement.

Comment ?


Depends on what you mean by "safe." How about positive flotation? Is
"heavy displacement" inclusive of a high ballast/disp ratio?

The main thing that heavy displacement boats offer IMHO is a smoother ride.

A regime that you could persue yourself, with relatively lo-tech &
lo-budget means, is to tape a ruler to your waterline fore and aft.
Bring aboard a known weight, and see how much it takes to immerse the
boat per inch. The next level is to do an incline test and measure how
many foot-pounds of righting moment the boat generates at varying angles
of heel; do this for the boat when stripped light, and when loaded, and
then you'll have some useful information that most sailors take for
granted. It'll also help test how secure your stowage is

FB-
DSK