"Roger Long" wrote in message
...
What I really meant was: Insufficient damping combined with
first or second order correspondence of excitation cycle with
natural pitching period. The significance of Radius of Gyration
and rotational inertia may be greater in terms of resonant carry
over of motion than gross value and counter intuitive results
may be experienced when adjusting weight distribution.

Translation?

The natural bobbing frequency of the boat is the same as (or a
multiple of) the frequency with which waves strike.

Answers?

1. Damp the boat's bobbing - make the forward pitch a different
stiffness from the rearward pitch. Then it won't bob so much.
Since that means changing the boat's lines, is a bit difficult to
do under way . . .

2. Change the bobbing frequency - shift weight from the centre to
the ends to slow it, shift weight from the ends to the centre to
speed up the bobbing. Leads to a lot of moaning from the boat's
crew, who specially don't like being dunked at the bow. And
hauling a couple of them up the mast, though more effective, isn't
popular either if you're going to windward - it's that lost
stiffness. And sometimes this doesn't work anyway (Roger's
'counterintuitive' thesis) if you try to slow the bobbing
frequency.

3. Change the wave frequency - alter course. Mind you, it might
take longer to get where you want to go, but just occasionally the
extra speed gained my cancel the penalty of shifting off course.
Do the sums . . .
--
JimB
http://www.jimbaerselman.f2s.com/
Comparing cruise areas within Greece and N Spain