I guess we are talking about the cruising proa where Im not sure a proa balances or compares well with a trimaran. I shall explain.

If Im to check it against a 9m catamaran, it is as though the cat is cut in half, and a half clear span bridgedeck adjoins a 40ft slender hull. Typically todays cats make heavy compromises to afford in hull accommodation, the hulls are wider and it is usual to find flatish and wide sections aft which can be better utilised by double berth spaces because that makes a logical distribution in the utility of using the boats volume.

It works out, but they compromise speed, and the actual volume provided will exceed most peoples space requirements. And this is important, for if it is excessive in that as it would be singlehanded, it defies its original purpose. What you have is more volume you can sensibly use, and you already sacrificed available speed to achieve what is likely a single double berth possibly mirrored two to four times through the hulls.

It seems to me sailing short handed with half a cat is a sensible proposition. And it will be more sea able,  faster and safer.

Tris on the other hand do offer a different distribution of volume where in the more difficult circumstances of restrained size it is floor area which is normally quite limited. Areas forward are too narrow but for using for the head, but there may be issues enabling a standing shower. Typically that leaves the wings of the hull for sleeping accommodation, and a double space aft as you indicate for a center cockpit design. But it does feel a little like life on a U Boat, crammed into all accessible spaces among the vegetables, dried meats and torpedoes. Im not sure I would like that.

Also, I once read a paper by James Wharram named 'Unsafe in any Sea', which highlighted the dangers of overpowered cats and the capsize issues of cats and trimarans tripping from beam on seas, where tris were particularly sensitive due to the low volume of the sponsons. If I recall it right, the paper determined via stability useful tris seem to top out at 30ft, where the utility of cats hull volume began to offer greater benefits. So it is interesting that the boats we are comparing are just on the cusp of these numbers. Compute within that the WW hull of a harryproa equivalent of the affected sponson has more volume, is taller, so has boundlessly more buoyancy.

Outside of the above generalisations, what 40F isnt doing is offering weatherly protected cabin space. Yet it is so very close to doing just that. That comfort is sacrificed to save something in the order of 50 sqft beam on windage and something in the order of 300 lbs in weight. As it would describe the existing boat with a 5m long by 2.5m cabin on the bridgedeck, taken from somewhere on top of the sleeping berth structures fore and aft, and from the WW edge of the WW hull to the edge of the present winch bases.

I know that at first thought, it sounds like such a cabin rather like an average cablecar in size would be a large burden, Now dont get me wrong I am aware that there are very good reasons why one would avoid doing that, but really what is being added is a low row of windows and a coach roof in place of the bimini. By eyeball measurement the difference in flat profile is some 50sqft additional on the existing 170sqft, it is so temptingly close.

• New Members 2