Rotating or fixed mast?

This article by John Shuttleworth, http://www.john-shuttleworth.com/Dogstar50-article.html, is for a 50 ft catamaran, but it is the best thing I've ever see regarding multihull flare and topsides design. You could do a lot worse than to apply his ideas to your trimaran.

Ian Farrier's sections for an F22 (http://www.f-boat.com/pages/trimarans/F-22.html) show one approach to sizing the flare.

Your sections look more like a monohull design, with all the action happening on deck. You haven't shown where the tramps attach, but presumably they go to the gunwale, at the same level as the deck. With a trimaran, the action happens on the tramps to either side of the cabin.

The cabin for a small tri needs to extend well above the tramp to provide adequate room inside. Cabin topsides that slope inward make for a comfortable surface as a backrest when sitting on the tramp, and provide for storage behind the seats. Winches on the cabin top are then at a comfortable level for crew kneeling on the tramps.

 

Thanks Tom - great article. I have seen the F22 before but now understand what you mean. To answer your questions, the attached picture has lines drawn to show approximately where the beams attach, the lower ones being the original A Class beams, now telescopic. The top beams disengage at the ama ends and fold up for towing.

The black line drawn round the hull is what I think everyone is suggesting is meant about raising the flare and so long as they fit into the available space, they can be changed as much as needed. Have I finally got the message?

Regards

Alan