I have found the recent threads very interesting and thanks to all for
their contributions. One thing has been bothering me though. Talk has
been of large proas at high speeds. I assume these are designs for open
ocean. 12m, 15 m and speeds of 25 to 30 knots have been mentioned.
This seems unrealistic to me and would be designing for an ideal of high
wind with flat water and no waves. Having sailed offshore, I know that
a 10 to 15 knot trade wind that has been blowing for a few days normally
kicks up a 2 to 3 meter swell. Going 25 knots on a 3 meter swell with a
light boat could launch you into the air. These waves are what limit
your speed as their tops crash into beams, superstructure, or you. If
one is designing an offshore cruising or racing boat, wouldn't it be
better to design for max efficiency at a more realistic speed? Say 10
to 15 knots for a fast, offshore multihull? This seems more realistic
to me and may result in a boat that was more all round, easier to keep
"in the groove" and possibly faster.

As an illustration, I have a friend currently sailing from Galapagos to
Marquesas. His average speeds have been between 6 and 7 knots on a 35
foot catamaran that in the same conditions in flat water would probably
be 12 knots or better. The pounding and smashing if he pushes the boat
is always so bad that he has to limit the speed. On my heavy 36 foot
monohull, I have made passages in the same conditions in less time, due
to the fact that I can push the boat harder without beating myself or
the boat up. Everything says the multihull should be much faster than
my heavy monohull, yet I know offshore, the reverse is true.

Something to think about.

Cheers, Paul