I try not to respond to posts that verge on personal attacks, or are intended to provoke discussion or argument I really don't care to get involved in. Erutan loves to argue.... I don't dignify it by calling it debate. He has contributed significantly, but I often find his pugilistic style annoying. He's a bulldog who once he gets his teeth into you simply does not want to let go. He has to "win" in his mind, or he's not satisfied.... He's welcome to be "right" if that makes him feel good, and he has a bone in his teeth to sell me on an HP. My 9M lOA parameter frustrates him, and even more, the fact that I refuse to explain or justify it to the world or to him, leaving him no ground to attack it from.... I noted that he recently reiterated this frustration after Rob's diatribe against me. ( I didn't take the latter personally.... I like and respect and admire the guy and he knows it, but I managed to step on his toes.... at least in his eyes.).
It has never even remotely been my intent to sell anybody on building a 30' catamaran, and if my posts have come across that way to some, it is not that they were written in that spirit.
Rather interestingly (to me), I did some numbers yesterday and discovered that Bernd Kohler's KD 860 is almost exactly the same LWL as Sagitta, though it is 61CM longer. Comparisons of location of the bridge deck cabin revealed some interesting things as well. The cabin does not provide the panorama I want, and the outboard hull side lacks the width for a good countertop work space, which is important to me, as I hope to spend years as a liveaboard voyager. The knuckle on Sagitta / Eclipse gives the workspace I want at the one time cost of labor on the lower hull..... but that's a one time cost. After Richard offered the Eclipse hulls cut down by 6" freeboard as an option on Sagitta, I began looking at how I could reduced LOA to fit within my length parameter. The Eclipse hulls are fatter / more displacement per foot, and my proposal to "fatten" the hulls on Sagitta led to this concession. Buff bows result in a hull 30 cm longer than my target, an I feel with some minor mods, that could be reduced to 9M LOA & 8.90M LWL. Slightly shorter bows / blunter entry, and a slightly modified curve so I can clip the transom without dragging it. I don't see any real value in a sugar scoop or reverse transom that would be lost by steepening it slightly. If used for embarking from a dinghy, a good stainless steel hand rail is of more value than a shallow angle. Below are drawings from the Sagitta study plan and KD 860 study plan. Note as I said above that the LWL is virtually identical. It's worth noting that Pete Hill's Oryx, a modified KD has a knuckle, obviously for the reasons I mentioned, and that Bernd extended his bridge deck cabin out past the hull on his larger Pelican design, such that what would be the bridge deck on the inside, formed a shelf on the outboard side.
It's always easier to build to plans than to strike out on one's own, and Woods uses a fairly massive mast beam across the deck in the cabin for structure, where Bernd uses a complex of intersecting structures including a forward bulkhead at the forward end of the transverse berths, combined with the curved leading edge of the bridge deck, and the longitudinal divider that adjoins the forward saloon bulkhead, which is also structural, to created an extremely strong step for the mast. This is a more intelligently designed structure, but does not lend itself to what I need.
Rob's fore and aft rudders are exactly what I was looking for. They offer the kick back function, as well as adjustable depth. They also offer an option that looks to be of great value to me. Cats are known to have difficulty tacking, and often require back winding to finish a tack. By deploying the forward rudders starboard and aft rudders to port for example, a very rapid centerless rotation should be possible..... probably double the rate possible with aft only rudders... or more. They also make it realistic to dispense with the daggerboard and case.... Note the huge rectangle at the aft end of the saloon....... that's the daggerboard case. LAR keels give more draft than I want, though I would like to have shallow "sacrifice material" beaching keels. The LARs are shown in the drawing below also. It is interesting to note also that Bernd shows his transom at exactly water line while Richard shows his above WL.
I continue to toy with options, as I am not yet able to build. I'm hoping that by this time next year I will be starting the build. In the meantime I will be experimenting with materials and techniques. I'm leaning heavily toward building the entire boat in foam sandwich instead of using cedar strip on the bottom. I also plan to experiment further with compressed construction foam. I've been able to achieve properties I like. Some flex and resilience is often better than absolute rigidity. Next month I will be purchasing some Divinicell H80 to work with. I also have not yet visited the local mfg that claims he can produce XPS with high density and excellent physical properties. I long ago wrote off XPS as garbage.... think foam coolers. The reality is that I am not closed minded.....
Howard
On 09/08/2018 06:07 AM, Mike Crawford wrote: