Best Rig Type For Downwind On Power Multihull

Sorry PAR, you are correct. My rig would NOT be easy to take down and rerig.

Perhaps I misinterpreted the posting as referring to a rig that could be put away (not unstepped) when not sailing, and not interfere with other activities such as fishing etc.

This might be the wording of a non-sailor (lowered and out of the way) ??

 

Agreed, or at least it does appear so, but isn't this what you should expect from the average powerboater?

 

Biplane sails

The simplest I can think of is a variation on my rig with two freestanding rotating masts. This rig I used on my own boat and on other of my designs. The masts have been foldable on some designs. Today I would prefer some form of Hoyt booms instead of those shown in the attached illustration.

JS

 

Masts and sails are nuisances on true power boats, and are plagues on multihull power boats.
You have to design all the structure to withstand the stresses of the rig, and to make compromises on the general layout.
All that has a a weight not well placed, high above the desk.
All that has a high penalty drag.
It's expensive, masts sails and the hardware are far from cheap, you would be very surprised by the bill. Far more than the two outboards if you consider all the modifications.
You'll need imperatively rudders, no way to control sails without rudders and some form of keel. If it's a fixed appendage it's drag again.
All this is cost and complication for a no gain of speed, nor fuel savings.
And all that only to be used downwind as assistance? I ask that because downwind is the worst allure for a sail multi. I won't enter in the details, make a search.
I do not see any advantage, but a lot of complications and problems.
Or you make a motorsailor. That is no sense on a small 30 feet catamaran, which purpose is to be simple and cheap for coastal use.
I you want absolutely to try a sail assistance go for a kite. Make a Googgle there several, and the installation is pretty simple. The cost is very low compared to a complete rig, but that doesn't mean that it's cheap. The kite and its hardware will be as or more expensive than one of the outboards.
It can be used as an auxiliary in case of malfunction of the engine, we have made trials of a small sport kite on a monohull monomotor and that worked pretty well, making the boat able to go back to the coast at 3 knots.
But generally catamarans have two engines as it's the easiest, most efficient and simplest system for a motor cat...So the need of a sail as life saver?
If looking for an auxiliary power system in case of... I would go for a chinese sculling, surprisingly efficient for moving a boat. Lol.