What is stopping a cat being as wide as it is long?

yea I know that Cat sketcher just wanted to hear DougLords reasons. He seems to think wide cats are good, but hasnt said why he thinks there are NO successful square cats out there. (which was the thread title)

The main reasons as I understand is the beams are too heavy and they wont tack properly.

 

I think the wide cats are also very slow in light air
Old Nacra 20 versus new one for example

 

beam

=============
I beg to differ a bit: Hydroptere.ch is 96% square, Alinghi was 75% square and tacked on a dime. Design is compromise and there are many reasons for choosing a narrower beam-tacking is just not one of them.
My conviction is based on numerous RC multihull experiments that showed that beam did not prevent tacking which is the primary argument I've heard against wide racing cats.
The best argument against wide racing cats is that in light air they'll be pinned to the water-- unless they have the SA to fly when the skinny cats do and then they'll be faster.
Catsketchers argument seems like it would have validity in cruising cats or cats with no movable ballast and no foils. Foils have and are changing the design of racing catamarans by allowing much more beam with control of pitching greatly enhanced by the foils. Any high speed racing cat can benefit from lifting foils to prevent pitchpole or ,at least, drastically reduce it.
--
All that being said, for speed I think a well designed foil equipped trimaran can win every time.

 

Doug; hydroptere.ch is a foiler, with foils bolted a cat, but it's not a "true" cat. The stability is obtained with very sophisticated foils. That's as far from a beach cat that a small rally car is from a Formula One...

The true problems of square cats (that's known since more than 25 years):
-Scotched in the water in light/medium light weather as it's difficult to get safely a hull out of water. The penalty of the wetted surface is horrendous. And you see all the others guys running away...
-Weight of structure. The mast of a cat is on the beam (ie nowhere) and the problems of flexing of the beam are excruciating, even with carbone.
-Discrepancy between longitudinal stability and lateral stability. The diagonal capsize arrives very fast with no warning. On cats, going downwind is a bad idea, better to tack and keep the apparent wind just behind the side. Longer way maybe but much more speed and control of the situation. The power/depowering is done with the main sheet and the rotation control of the mast to open the upper part of the sail. We are on a "small" beach cat with just the feel of the crew to keep all that upright.
- It arrives a moment where bigger sails are difficult to control just by human strength with blocs and tackles.

As there are a lot of races and raids, everything has been experimented. Even the craziest. And the largest beach-raid cats for 2 guys are around 21-22 feet, width around 60-65% of the length, "wings" and all the sail that 2 strong guys are able to control fastly and accurately. After efficiency goes down. Too much sail and it's impossible to control so the capsize will punish you. Semi foiler cats are a bit better but on a beach cat it's maybe marginal.

It seems to be the best compromise with the nowadays technology for "classic cats". After you have to go to foilers, no way as you are at the limit of the performance of a slim displacement hull. Planing hulls have been tried and it's not highly successful. Not good around for racing. I do agree with you: a tri foiler will be faster

 

===============
You're partially right. It is designed to function as a "normal" cat, a planing hull cat(with variable geometry stepped planing hulls) and as a foiler-all depending on conditions and sailed with combinations of stepped planing hulls and foils as well as with foils and steps retracted. It appears to function well in all three modes.
I think there would be a lot more "beachcat-like" cats closer to square if the trailering problem wasn't so expensive to solve. A beach cat using foil assist including rudder t-foils like hydroptere.ch could be significantly faster and just as controllable(foils provide excellent pitch control especially when a t-foil is coupled with a forward lifting foil like a curved daggerboard) as any current beach cat but would probably be able to have a better SA/ws ratio and enough sail area to have the hull flying characteristics just as good as it's lower powered narrower sisters.
But we agree on the tri being the fastest and thats good.....

-pictures show the bow dropped down to form the step used with and without foils--
L to R- 1) steps deployed, foils deployed, 2) foils retracted, steps deployed, 3) steps retracted, foils retracted.
click on image for best detail:

 

With Hydroptere.ch it would have fairly unique tacking or gybing dynamics I assume the boat would rotate around the point where the foils are touching the surface so in effect the boat would be narrower than its true beam. I suppose the trade off also of the type of foil the boat uses is that the beam between the contact points of the foils decreases as the boat rises hence the necessity of the square platform to maintain stability.

I can recall reading Alain Thebault's description of the boat landing violently on its floats when the foils occasionally ventilated sounded very hairy, my respect for his courage increased markedly!!

 

==============
You're absolutely right but even Hydroptere.ch is a compromise since it is designed to sail well in three different modes as described above.
Hydroptere, the fastest sailboat on the planet, is 59' long and 80' wide and is designed to strictly be a foiler. It flys high and when doing so max RM decreases which is why they carry water ballast in the windward ama. As far as I know .ch doesn't carry water ballast.