dh@. wrote in :

So is most of the bouncing caused by the ropes, and the
boats bouncing around between and because of them?



Nope....It's caused by "reflections", standing waves caused by the
initial wave reflecting off the hard surfaces of the other boats bouncing
around.

A wave is stored mechanical energy. It does two things...gets absorbed
by doing work like lifting boats and floats...or...is stored and
regenerated as more energy, bouncing off fixed objects or being
regenerated by moving objects in various odd directions caused by their
position and shapes.

When the wave lifts your boat, for instance, some of the wave is
immediately reflected back towards it source by the hard hull. Other of
its energy is actually STORED in the boat's mass by lifting the boat out
of the water. This stored energy is mostly regenerated when the boat
goes over the crest and its mass forces the boat hull back down in the
water, causing a new wave radiating out in all directions from the
hourglass hull. So, we made new waves and lost a little energy in the
air resistance of moving the boat and water resistance of moving the hull
in the water. Those docklines also absorbed some of the energy and got
hot when you stretched them out and back.

As you can see, if we compound this physics lesson by 200 boats tied to
floating docks going up and down across a marina, waves bouncing off
fixed bulkheads, piers, pilings, the marina soon turns into a mass chaos
of regenerated/reflected waves that seem to go on and on and on long
after the initial waves from a passing boat have gotten lost in the
mayhem. All this energy came from the motor of the waking boat....or the
wind that made normal waves across the harbor.

Of course, even more complex waveforms result from that young guy and his
new girlfriend you can hear screaming through the hull, five finger piers
down F-dock...(c; These are easily identified, compared to normal waves,
as they increase in intensity and become very irratic just before they
stop...(c;

Larry
--
Any boat seemingly rocking excessively for no apparent reason is best
left alone until the violent oscillations and internal screaming stops.