Proa Crossbeam Design Help Needed

I'm building a 30' light cruising proa based on CLC's Madness, but with some changes.

One of the things I want to change is to simplify the construction of the crossbeams. Madness has very nice aerodynamic cedar strip crossbeams but I want something simpler to build, and to use less carbon fiber (none if possible).

A simple box beam or a Wharram style 'I' beam would be great, but I don't know how to calculate the dimensions and the scantlings for these to make them strong enough, but not excessively heavy.

The boat will have a main hull with a displacement of about 900kg, and an outrigger with about 180kg.

The crossbeams will be about 4m long (center to center of the two hulls).

Can anyone advise about how to design the crossbeams?

Thanks!

 

Have you approached CLC ?
That would be my first stop.

 

A box beam is required. An "I" beam has no torsional stiffness, which is required in the cross beams.

You can get simple formula based upon the vessels principal dimensions from rules such as GL/BV etc. for the cross beams.