T&T: ART

[Dave Cooper]

Seahorse John wrote me: Ummm, aren't you gonna tell 'em about when ART
cannot do his job?

to remind me to tell the whole story on ART.

I was remiss in not telling that is gets overwhelmed in large steep beam
seas that toss Swan Song sideways. We had one 15' odd footer on the beam
that I was looking up at it when she hit. Swan Son went directly sideway for
a bit. Nasty but we recovered. Our max roll on the passage from Cartagena
was in the 20 degree range. The wave period was shorter than Swan Song and
most tops were tumbling on themselves. In any wave period under 4 secs it's
performance is degraded. The time it takes for a cycle of water to go from
one end thru the baffles to the other end thru the baffles and back is 4
sec's. This is our roll period so the tank must keep the water 180 degrees
out of phase with the boats roll. I would suggest that any other method
would also have degraded performance in these condition based on my
experience.

The trouble with all this is that you can't have the same boat with all
types of stabilization systems and just switch from one to the other. Not
something that that powerboats reports could have tested.

OTOH, the inter-island ferry cargo/ferry boats some of which are 80 odd ft
were showing their whole bottoms and props as we passed them. So I think ART
was keeping us from that fate.

We also do the usual fall thru waves in confused seas...ART is no help there
at all. Big acceleration and a big splash at the bottom. A good plan there
is go slow. A better plan is not to be there.

Thanks John for bring this up!

In reading my prior post I made a typo/mistake in the daytripper passenger
count..it was 1000 not 3000. Sorry but need to keep those mistakes
corrected.


As always YMMV.....


Dave & Nancy
Swan Song
Roughwater 58
Hawaii Passage '08/09