I agree, long slender hulls is the way to go.....I guess there are
different opinions on what long and slender is.....I think 12m for an
offshore hull is too short. 15 m starts to get more workable but the
longer the better. This is my opinion but it seems to be confirmed with
the experience with the offshore racing multihulls.
I am most impressed with Ini and his Gaia's Dream. To me, if I was
cruising offshore in a proa, this is the boat I would like.
http://www.youtube.com/watch?v=3H0qPgS1_XE
I would love to see a Harryproa built in this size.
Paul
Rick Willoughby wrote:
My actual experience is limited to small slender hulls, high speed
planing and semi-planing hulls and dabbling with submerged buoyancy.
There is significant difference in the accelerations in a slender hull
compared with typical planing hull or even a buoyant cat hulls.
It is possible to go fast without getting hammered.
The best is submerged buoyancy and foilers. These can be almost immune
to surface waves.
http://www.youtube.com/watch?v=kRuUtOmMGR0
<http://www.youtube.com/watch?v=kRuUtOmMGR0>
My version was immune to waves until they were high enough to submerge
the seat:
http://www.rickwill.bigpondhosting.com/v8.jpg
<http://www.rickwill.bigpondhosting.com/v8.jpg>
Then there are the wave piercing hulls like Earthrace and MarySlim:
http://www.youtube.com/watch?v=6qfibvmuJlw
<http://www.youtube.com/watch?v=6qfibvmuJlw>
The LCS 2 is another variant:
http://www.youtube.com/watch?v=5RgfwrXevNU
<http://www.youtube.com/watch?v=5RgfwrXevNU>
The big tris make tremendous speed in gale conditions:
http://www.youtube.com/watch?v=43DikdhEaVg
<http://www.youtube.com/watch?v=43DikdhEaVg>
One clear virtue of the harryproa is the ability to build a
wave-piecing lw hull that can be long and slender without volume for
fitting people. The rest of it needs to be sufficiently clean
aerodynamically so it does not slow the boat appreciable when the
wavetops clip the structure.
A flat bottom on a narrow hull does not pound. The hull just passes
through waves with very little increase in resistance.
Rick
On 26/07/2010, at 1:01 AM, Paul Wilson wrote:
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
Rick Willoughby
rickwill@bigpond.net.au <mailto:rickwill@bigpond.net.au>
03 9796 2415
0419 104 821
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