"reverse" trimaran

The difference is that a purist trimaran spreads all the rig and sailing and appendage loads throughout the deeper and longer main hull; that element does all the hard work - whereas a cat like Decision 35, which has conventional cat length/beam but carries racks to make it square - which doesn't count in overall structural beam, just perching/righting crew platforms (also crude aerodynamically, imo) - back to subject, and with this ******* tri/cat's "half" depth/length central "hull" --- is still a cat - meaning the central long pod is cantilevered between the two main hulls/floats (a passenger) and relies almost completely on the connecting beams for platform rigidity, which it doesn't do, compressing and bending and hence all the problems we've seen on Oracle's earlier bendy, twisty platform ... whereas the tri is like I said, a totally different fish, a more structurally sound (and faster) fish.
Just saying.
This might start a long and savage thread response from various camps. Cheers.

 

I'm sometimes wondering about the same thing. When a racing tri like ORMA 60 sails on one float the main hull is only providing structural integrity, otherwise it is just along for the ride. Suppose you replaced the main hull with some sort of truss or I beam structure to take the mast loads, but stay clear of the water at all times a major reduction in weight would be possible allowing better sail area/weight ratio. In multihulls less weight usually means faster boat.

 

Here is a photo of Team Lalou's new Multi 50 trimaran I think it exhibits nicely why the idea in the post above is not functional or desirable. It's just impossible to get the same structure in a catamaran as a trimaran as the low freeboard would make the catamaran undesirable in terms of seakeeping and imposes a huge drag penalty when the truss structure contacts the surface of the water. It would probably be ok in a lake sailor but offshore or in choppy waves hopeless.

To make the idea work you would have to give the outer hulls much more freeboard which would impose greater windage and weight and negate the advantage. The other option would be to drastically increase the beam clearance which would once again add large amounts of weight and windage both approaches have the very undesirable effect of raising the centre of gravity. The other point is you are not always flying hulls and what happens when your in a low wind situation with sloppy seastate and swell surging over and through the truss structure? In a trimaran you would still be making some reasonable progress in a truss centred cat the drag penalty would be huge.

 

Isn't that what is on the Oracle 72?

 

I must agree, if you are flying two hulls, then the structure must be able to take it, and if so, you can eliminate the third hull. Because of rougher water? I'm not buying it. Only if flying two hulls is just a momentary stress, then I can see it.
The drag in the water from the hull is going to be MUCH more than the windage of the crossbeams, so for racing, I've got to believe a cat is going to be faster.

For my cruiser design which will not be flying any hulls, the third hull increases load capacity, and my design is to have the engine in this hull and the fuel tank, all completely isolated from the living quarters (the rest of the boat).

JackB

 

But in amost every case where the same length tri raced the same length cat the tri has won-from Victor T vs C Class cats in 1969, to Adrenalin in the F40 class, to BMW17 vs A5 in the last Cup, to Mediatis Region Aquitaine(parliers cat) vs Orma 60's and on and on.

 

catsketcher

I know is not the subject of the topic.
Could you put numbers and units (kg/meter of lb/feet) in the sentence?

I am building always too heavy
Thanks

Joe