Malcolm wrote: Your informant was quite correct as far as he goes. However our experience with the CS hull as applied to motor sailers shows that it is possible to apply a power boat hull form to a sailing catamaran to produce a boat with superior sailing and powering characteristics. It is the longitudinal rocker that the sail boat requires to enable it to tack and minimise transom drag that restricts its speed and leads to "squatting". Brian replied: Totally agree ____________________________________________________ Malcolm wrote: The CS hull removes this rocker and results in a much less "displacement" of the water flow. Straighter water flow equals less resistance. Brian replied: Don't know that I would agree with this claim....The CS hull appears to trade some longitudinal 'displacement' of the water flow for lateral displacement around the canoe underwater shape. But the CS hull form does provide more buoyancy displacement in this aft zone where increased 'velocity of flow' occurs from greater propeller induced flow (higher HP on faster power cats)that produces a decreased pressure zone, and ultimately squatting. So while I really appreciate Malcolm's contribution to the catamaran hull forum with his CS innovation, I don't feel it represents any significant 'straight line' decrease in resistance thru the water. _______________________________________________________ Malcolm wrote: The CS hulled motor sailer motors well and sails well. The only compromise is that they do not tack well, due to the straight keel line. This might be a problem on a round the buoys racer but is not too much of a problem on a long range ocean cruiser. Brian replied: I agree with you here. The extra depth of the bow could offer extra resistance to slow or stall the tacking process in light winds & slow speeds. The sterns are a different matter.'Kicking' the stern up as in many sailing designs, appears to provide for a stern that might move laterally more easily (slide sideways to help facilitate a tack). But in reality you have a big rudder and often prop gear back here that prevents this sideways movement anyway. So the sterns don't really slide sideways to facilitate the tack in either the sailing hull form, nor in the CS hull form. Rather these sterns follow the carved (curved) course thru the tack. Remember the worst thing we can do with a catamaran is push the rudders over quickly in an attempt to tack...the rudders will act like a brake to kill boat speed and the boat's ability to 'carve' a course thru the tack (turn). So the key to tacking the CS hull form really lies in the key to tacking cats in general...maintain some forward momentum to carve a gradual (turn) thru the wind, and don't do it while in a bow down attitude. _________________________________________________________ Malcolm wrote: The simplest way to counteract the diagonal downward thrust of the rig that your informant talks about is to move the rig further aft. The CS hull does have a fine half entry angle and would be prone to be effected by the height of the thrust of the rig[CE] so the hulls are made longer and the rigs moved further aft. Brian replied: Certainly the entry angle of CS is no finer than that of Gunboat. I do agree with moving the rig aft and lowering the CE, both of which I've promoted with my mast-aft, single masted ketch. And look at all of the new big ocean racing multis...all moving their rigs aft. And they are making their bows longer. I believe both Malcolm and I've said make your cruising boat a little longer than you might need for 'packed accommodations', but leave those extra ends of the vessel EMPTY. Then they are there for that extra buoyancy, and that extra waterline length, but at not a great increase in cost to build. Finally I repeat what Malcolm opened with, "However our experience with the CS hull as applied to motor sailers shows that it is possible to apply a power boat hull form to a sailing catamaran to produce a boat with superior sailing and powering characteristics."