A New Beach Trimaran

Your slenderness ratio 10:1 is not fast, more like 14:1 +

 

IDKFA- yeah i understand what your saying- the more sleek the better- that means at its widest - 14ft you have a 1 ft beam, at 28 ft you have a 2 ft beam and at 42 ft you have a 3 ft beam, .yes very true- that would slice through the water have low wetted surface and if there is good rocker and a round bilge design with wave peircing bow,combined with a huge sail area and rotating wing mast- you would have a racing design ...very nice , but i need a berth inside the hull- so i have kept the beam to a minimum for a comprimise..i may lose two knots with a 10: 1 rather than 14: 1 but i can sleep in it more comfortably and that makes the experience thoroughly enjoyable. 10:1 is still fast at 32 ft. better than the standard 5:1 or so on the farriers and they'll do 20 knots.

 

Actually, 10:1 would have significantly less wetted surface than 14:1 at same DSP. But ignore WS, not important, get the prismatic right and keep the surface smooth for high-end speed. One would have is significantly less wave-drag and that’s the limiting factor. (if didn't screw something up). Taper the freeboard to maintain your reserved buoyancy and allow for a bunk or shoulder room when sitting.

20ks+.... That's with spinnaker on a broad reach. Approx 2/3 of wind speed, so in 30+kns wind, or with a bit less wind and surfing on large quartering seas. Beam reach at high teens with risk of stuffing ama. On all other points of sail not even close. Average speed a few kns better than a monohull. I’m suggesting sailing at wind speed, and at much wider range of angles, with less effort adding, changing and adjusting sails. You’ll probably have two reefs in the main most of the time. Which probably is desirable most of the time single-handed blue water sailing and especially at night. No expert here, just a suggestion.