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wrote:
Most of the monohull sailors that I know who have sailed cats, complain
that the combined bow waves meet under the bridge deck creating a very
uncomfortable pounding.

Certainly, if you've never heard/felt the pounding, it would be
disconcerting and perhaps uncomfortable at first. I have to admit
that the first time my PDQ 36 cat surfed down a wave at 12 knots and
pounded when it hit bottom, I dove for the bilges to see just how fast
we were sinking! I learned quickly that pounding has a lot to do with
the angle at which you hit the waves. If you power a cat straight
into a chop, you will certainly pound, although I found my old Nonsuch
pounded worse in this situation (though perhaps not as loudly). When
we want to power upwind against a nasty chop, I'll set the main very
flat, pulled to weather, and powersail about 30 degrees off the true
wind; this almost completely eliminates the nasty pounding. One huge
advantage the cat has in this case is that we can maintain 5+ knots
powering against a 25-30 knot breeze with chop, while most monohulls
will turn back.

On normal points of sail, we have relatively little pounding in seas
under 4-5 feet. It doesn't really affect the boat's motion, its more
of a sound thing, with a little rap. Far more annoying are beam seas,
which can suddenly raise one hull while lowering the other. This can
be quite disconcerting because the cat is normally completely level,
and then suddenly lurches 10-15 degrees. However, this is easily
controlled by the helmsman, since angling the boat just a few degrees
to the seas (or wake) totally eliminates the problem. In fact, on the
ICW, I always waved the powerboats through, telling them not to reduce
speed for me since I should be able to handle it with no problem.

The beam seas problem is such an issue that in certain conditions the
autopilot cannot be used, since a firm hand, and anticipation, is
required to keep the boat on an "even keel." In this situation I find
that I have to stay on the helm for the duration, since my wife cannot
maintain the necessary focus for extended periods. I would not expect
the average monohull skipper to have this skill, and I often wonder if
this motion is what first time cat sailors refer to as "pounding."

This effect is said to worsen as wave height
increases.

Well, it doesn't happen much in flat seas! But the design of a cat
normally dampens waves so you can't say that a boat with 1.5 foot
clearance will pound in 2 foot seas. I usually don't give it much
thought until I hear "4-6 feet chop."

It would seem that the higher off the water the bridge deck
the less this would be of concern but there are obvious limits to this
approach.

The Victory Cats are designed with a high clearance - in fact by a
former PDQ owner who apparently wanted to reduce pounding. Our final
decision to go with PDQ was at a show where a Victory was next to the
PDQ and we found the "high design" rather off-putting. In particular,
the high freeboard makes the Victory rather inaccessible from the
side. I might imagine this is better for long offshore passages, but
is it worth the windage?

This issue largely goes away with modern larger cats, over 40 feet,
such as the Manta and the PDQ 44. They have been "scaled up" with more
clearance (and high freeboard), plus the larger beam reduces the beam
seas problem.

Another point - older designs, with solid foredecks instead of tramps,
tend to hobby-horse a lot more then newer cats. (And in some cases I
mean a *lot* more, as in a sailing pogo stick!) Add this to low
clearance and overloading, and you could have a boat that would pound
in even a modest chop. For this reason, I didn't consider older,
smaller cats, under about 32 feet.

My question- Is this an issue with tri's

Its a moot question, since there are virtually no cruising trimarans
being built. The light folding tris (F-27 and the like) have mesh
"decks" and thin hulls so there is very little to pound.

The folding tris and cruising cats are such totally different design
points that if you're deciding between them you should get more real
experience before buying either!

I would also be interested
in input from cat sailors as to how much this is an issue with their
boat and is the only solution increased height for the bridge deck?

If your intended use is coastal cruising, I wouldn't worry too much
about it. However, you should definitely get some time on any design
you intend to purchase. Just like there are major differences in
monohulls, there are differences in cats.