It will certainly be a
catamaran, approx 30' waterline, 12' beam, either a schooner or ketch, leaning towards a gaff rigged ketch with freestanding masts. Since I am limiting the beam so much I want to split the sail plan up to keep the center of effort low. A ketch, in my limited experience but abundant
research, seems like it gives you a lot of options and control. The hulls will have no
storage or accommodations, being something like scaled up versions of hobie 16 hulls but not quite as skinny, there will only be a very small, highly aerodynamic
cabin on
deck, everything mounted on an
aluminum frame. The whole idea is simple,
cheap, light, minimal windage, minimal
draft, and easily handled by myself alone and an eye to reducing/eliminating potential
maintenance and failure points. The loaded
displacement for myself alone should wind up being about 1200 lbs, with a sail area of 120-150ft2, divided between fore and aft masts, thinking about a 60-40 sail area distribution, with sails of 3 to 1 aspect ratio.
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I love your design ideas! I am building a quite similar cat, with somewhat similar goals, and using a rigid wing for power (in addition to some
electric motors...
solar panels... and a gasoline
engine for times when moving very fast or clawing off a lee shore is required. Mine will displace 3000 lb, about half the weight of a
Maine Cat 30. Mine shares your narrow beam dimension, and uses a small amount of carbon fiber reinforcement in critical areas, and is certainly of ultralight construction... at least for something that can cross oceans, survive a
capsize, groundings, etc. So I think you will find 1200 lb empty, (let alone with a person on board) hard to achieve... unless you make the construction pretty exotic.... or uncomfortable fragile.
However, if you are mainly interested in cruising in protected areas or only in places where the
water is warm (so you can survive a calamity), 1200 lb is possible without getting too exotic. And weight begets weight (and cost), so sticking to your goal can be a very good thing.
I am not at all trying to be a naysayer, and as if to counter what I just suggested re your design being too light. I submit this: A previous boat I built was 16 feet long, had three hulls with 20 foot beam, was powered by a composite rigid wing, and weighed just over 200 lbs empty, including the rig. For it, wing efficiency (expressed as L/D) was one key to its going several times wind speed. Working against wing efficiency, is Fh/R, the other ratio that determines sailing speed vs windspeed. Fh is heeling force (meaning the maximum heeling force that can be sustained as the boat sails in is designed attitude) and R is resistance (which, in this case, means resistance of the
hull through the
water combined with the component of aerodynamic resistance that aligns with the hull's path through the water). The wing from a sailplane is wonderfully efficient, but far too long (for its sail area) to be used on a sailboat. The wing of a c-class cat would look short and fat and complicated and gnarly on a sailplane.
So... for "efficiency" as the term is used in aerodynamics, a long, skinny, clean (i.e. no flaps etc) wing (exactly what you see on a sailplane capable of 60:1 glide ratio ) is just the ticket. But, for a
sail boat, all sorts of other issues com into play... and aerodynamic efficiency ends up being traded away for many many other reasons... even in boats designed, like my little tri, to go very very fast without regard for comfort or ease of sailing. The wing on a c-class cat, with its flap, slats, multiple sections, etc. trades away aerodynamic efficiency for aerodynamic power... so the coefficient of
lift is very high, but the coefficient of drag is necessarily also very high... albeit not so atrociously high as it is in most soft sail arrangements.
If you can live with having two sails, one per
hull, there is a lot to be said for that arrangement -- not the least of which being that you could find two 9 meter windsurfer rigs for next to nothing, if you uncover the right garage somewhere. (Actually the right two garages -- most well equipped windsurfers have several rigs, but not two identical rigs.) A hull makes a relatively efficient location for a cantilevered rig.
Another of "Ken's weird boats" had a canted rig. It was a tiny proa. An imaginary line normal to the sail and projected through the sail's center of effort went through the centerboard's center of effort, so there was no heeling couple. That meant that the boat did not heel at all... stead winds, gusts, etc all resulted in a flat boat. A little odd, and shunting was required instead of tacking and gybing... but all in all a pretty neat little boat. (Not an original idea on my part: there have been many others of the type, some vying for the outright sailing speed
record a while back.)
But to reiterate: cool design! I wish you success. Ketch (or yawl) rig is a good idea and I (personally) would not be overly concerned with things like slot effect (which doesn't happen in a meaningfully beneficial sense in sail rigs) or
interference effects either... which, if you are just reasonably careful, can be largely avoided. An "Aero Rig" is a possibility too, although the cantilever loads can mean a heavier structure than you might want at the base of the mast. Sailplane aspect ratios are typically 30:1 or higher, so much of the esoterica of aerodynamics is of little concern when considering realistic sailing rigs. The 3:1 ratio you mention is fine, although it wouldn't hurt to try for a little bigger number there (via square top rig, fully battened rigs, etc.)
If you have not already built a boat, you will (I hope) find the process itself (and especially designing your own boat) very gratifying. (It reminds me of
learning to fly. I've said many times that the process of
learning is justification alone -- that one can then fly places is icing on the cake.)