!. Do you know how to sail?
2. How soon do you want to be on the water?
Building the pieces is the least of your worries. It's getting the thing to work that will give you the most trouble.
On a monohull the position of the sail and the fin are important for safety reasons but can usually be sorted out reasonbly well. I've only seen a few discussions on how to set up a tri and they were all based on dimensions from some commercial unit.
A wind powered boat has to be able to manuever on command. If it is slow to respond it may not tack and, thus, become useless. I just read a query from a guy who adapted a well known tri set-up to his kayak. The judgement of the designers was he would have to use his paddle to get the rig to change tacks because the central hull had so little rocker. Not an insurmountable problem but, I have been in situations where tacking was so tricky that the last thing I would do is let go of the controls to grab a paddle.
Where you are going is even further off the map. You may get lucky and have the thing work the first time out but, I wouldn't bet on it. You will likely have to be your own developement department and try to massage this thing into a workable unit.
If you are in this for the long haul, go to it.

: .. a bit eccentric?

: I am hankering for a project over winter, if for no other reason than to,
: again, put off painting the house.

: I have built a 22 foot by 22 inch double and would like to ad a sailing rig
: (as per the Tassie paddlers) but think that my boat is too unstable to
: take any real wind load.

: So… I then thought about a mini trimaran with two narrow outriggers, but that
: would mean designing and stripping two outrigger hulls, which would mean
: lots and lots of time, all for soemthing that may not work.

: What about an outrigger system that relies on “Flyak” style foils to give the
: lift? The flyak system gives at least 90kg of lift at say 9 knots, which
: is heaps for what I am after.

: The advantages are: 1. I can claim to be working on something unique, which
: gives me a better chance of avoiding the painting.
: 2. I can get away with one cross sectionional piece, not two.
: 3. It will (I think) work better at the speed increases.
: 4. The vertical section (going down to the foil) may act as the keel?

: The downsides are (at least)

: 1. I haven’t the faintest idea on how to design a foil.
: 2. It may look stupid.
: 3. If I go too fast and pitch pole the boat, my partner will not go out with
: me again. Or perhaps more soberly, am confident that a trimaran will work,
: but am not at all confident at this idea.
: 4. It may well not work well in the open ocean. That could also be said of
: the displacement version of the trimaran.

: What do y’all think? Can anyone point me to saiboat design websites? And,
: does anyone know of a foil design program that covers blade area, shape,
: pitch, and drag at various speeds?

: Cheers,

: Matt