Prismatic for a trimaran?

DCockey. Beside Tennant approach Shuttleworth on his 42 foot open wingdeck cat designed it so that the Center of Buoyancy moved forward as the bow dipped due to heeling or pitching. The idea is to do the same as an asymmetric hull. Asymmetry of buoyancy also helps to minimize pitching. If every thing is in one line it pivots around that line, if you have separation you have some resistance to pivoting (pitching). Shuttleworth wrote about this in the original write ups of the 42 cat.

 

Only if the LCB is aft of midships, not fwd, as placing outriggers fwd would be suggesting!
To minimise the pitching requires fine angle of entry and slim bows, as this also reduces the WPI and any restoring force from the bow.

 

Trimaran design is very complicated compared to monohulls or catamarans. Because you have two very different shaped hulls doing different jobs. The trend these days is to have a very fine bowed main hull with significant rocker and maybe almost a hard chine hull in cross section. The outriggers have very little rocker, a wide transom and buoyancy low down.

I assume you are designing as a paper/screen exercise, and don't plan on building the boat??

Richard Woods of Woods Designs

www.sailingcatamarans.com