If you were prepared to be really radical <img src="http://www.catsailor.com/forums/images/graemlins/grin.gif" alt="" />

I could easily make a 20ft version of my 4 hulled boat down to 75kg, just substitute the Al beams and submasts for carbon and glue the beams to the hulls.

The biplane windsurfing rigs allow you to easily get different rig sizes just like on a windsurfer. 3 rigs 12m, 9m and 6m would give you 3 rig sizes 15m 18m and 21m, which is still quite inexpensive and lightweight. Total rig weight, mast, boom, sails, blocks, stays etc is 25kg for a 16sqm rig. How does that compare to a conventional rig?

Also you can carry a much higher sail area for a given wind strength on a biplane rig.

I could probably make a cat by having a soft central "hull" bridging the front and rear hulls and not increase the weight by much.

Gareth
www.fourhulls.com