>>Now my question is whether full bows and stern pitch more than slender bows<<
Well absolutely, full bows, buoyancy, lift = rock around the clock ride, add more power have more roll
Wave piercing bows, less buoyancy, potential to submarine or degrees of less, flatter attitude and commensurate better ride.
didnt think of this but seems to be true, so what is needed is a good degree of clearance, something commonly discussed among cat design devotees. The first adequate clearance design was the Catalac, which was said to have 800mm clearance.
There were people that suggested they had never had the boat slam and yet had 1,000s of sea miles. But it also depends upon what the ratio to clearance and beam of the boat is, Im frankly without any numbers on how that might compare, but eyeballing some late designs in cats seems to hold less than 800mm by a good measure. Cruiser 50' we dont as yet have any data but it looks to be in the zone in the crucial middle zone.
Some other considerations, I remember designer Perry talking about how important it was how a boat left a wave, and nominated angles of around 15 deg. Of course we cant do that as this boat has to travel both ways with reversible bows, so a flat bottom with rounded sides and a tip up at the bows while still immersed seems like it might be a good option. And I am I confess a person who is far more concerned about wakes than pushing through waves, being of the school that suction being the viscous and more powerful force. I think energy recovery could actually be quite good in such a boat.
One thing on the Heavenly Twins with more or less no clearance at all. They come with rather canoe bows with a progressive curve from the gunnal to the keel but tend to hobby horse a lot. One particular fella, an ex clearance diver with a boat named Grey Dove (you can google it) fitted plastic extensions to the bows to give a quite attractive plumb bow wave peircing design. The hobby horse motion gratefully disappeared and he gained a additional speed due to extra waterline length and probably not wasting quite so much drive.
some deck clearance data gleaned from about the place:
Heavenly Twins 26' 275mm Aft (Not counting the nacelle, which has zero clearance)
Patterson Twins 34' 400mm Fwd.
Woods Banshee 35' 420mm Aft (But seems pretty level)
Woods Flicka 37' 300mm Fwd
Dazcat 9.2M 500mm Fwd.
Woods 36 "Scylla" 725 mm aft
14m FP Casamance 750mm aft
11.7m Spirited 380 - 505mm
Prout Escale 34' 400mm Fwd, 230 mm Aft.
Solaris 42: 250mm
13 metre Outremer: 550mm
Woods Banshee 35: 350mm
12 metre Azuli F40 :630mm
Gemini 105MC: 200mm
Dazcat 1190: 400mm
30' Sailcraft Iroquois: 355mm
12.5 M Schionning Wilderness 800mm
Prout Quest 33CS: 180mm - 100 mm Nacelle
38 Solaris Sunstar, 600mm
Lagoon 470 750mm
Schionning Cosmos 930mm
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Posted by: robriley@rocketmail.com
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