Great posts guys, thanks!

I just want to add a relevant detail regarding the trimaran design: its amas aren't paralel to the mainhull, they have a built in bow down atitude at rest. The ama bows touch the water first, so the boat can stay upwright at rest, its weight resting mostly on the mainhull.

The cat's trick is to make both floats with a bow up atitude that allows for long bow overhangs. Those are supposed to sink as windspeed and boatspeed increases, so as to enlarge the waterline. In light winds, however, the waterline will remain close to 90 ft unless ballast is used - which doesn't make sense in light winds.

Both are interesting approaches to the same concept: explore the large overhangs allowed by the absence of a max LOA.

I like the trimaran solution best, after all it looks a lot like my boat grin grin grin, but there is another reason for my preference, and it is best explained by John Shuttleworth here.

If you don't want to read it all, the key part follows:

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Now I should like to discuss the outrigger which is different in shape to anything tried before, and contributed enormously to the success of the design.

In order to look at the distribution of buoyancy along the hull we first have to look at a very different sort of boat - Eric Taberly's Paul Ricard. One of the significant things I noticed about this boat every time I saw it sailing was that it did not pitch. The reason is all to do with the position of the foil. If you look at the drawing of Paul Ricard in Fig. 3 you see that the lift of the foil is well in front of the centre of gravity of the whole boat.
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This produces a couple which resists the tendency to pitch. What is more important however is that the centre of lift of the foil stays in the same plane as a wave passes. Unlike an outrigger where the peak of the wave will move the centre of buoyancy aft as it passes the hull. And of course this will push the bows down (see Figs. 4 a and b).
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So in order to try and keep the benefits of the foil yet still use an outrigger I pushed the centre of buoyancy well forward and cut away all excess buoyancy low down at the stern leaving enough buoyancy distributed along the length of the outrigger to stop the boat from capsizing across my diagonal in favour of going over directly sideways.

So if you consider the outrigger shape shown in Fig. 4c it can be clearly seen that as the wave passes the centre of buoyancy of the boat the profile is rising and the wave does not push the bow down again and hence the boat does not pitch.


In short: besides allowing for the long overhangs, the tri with inclined amas also reduces pitching in waves and benefits from the largeer waterline in all wind strengths, regardless ballast weight or position. But we will only know for sure if it is the best solution or not when the sail side by side.

Can't wait for the races.

Luiz