Jim … Will give it a try, although a couple of sketches on a napkin would be easier.
Compare the leading edge of a jib between most normal r/c monohulls, and same with a real boat. On a real boat the leading edge of the jib is attached at the very bow of the boat and directly in line with the center-line of the hull. In order to sail as close to the wind as possible, the angle between the bow (and jib luff) and the direct line to the windward mark provides the direction the boat is sailing. Thus (in concept) both the leading edge of the jib, and the bow of the boat are sailing as close to the wind as possible - based on the jib luff. As the jib sheets on a real boat are tightened or loosened, the boat will be able to “head up” or will have to “fall off” to maintain same hull speed. Thus full jibs have power, but not necessarily speed unless they foot off.
Now, looking at your sketch, if the leading edge of the jib is off the center-line of the boat and to “weather” of the hull, in order to prevent a backwind of the jib luff, you would (in theory) have to foot off slightly (or a lot) to keep up the same speed. Generally, you are trying to sail with the jib luff as close to the wind as possible. If the leading edge (luff) of the jib is 10 degrees off the center-line of the hull, then to get the luff back in line, the bow would have to fall off about 10 degrees.
The offset jib is something we get to deal with on models, as we don’t have a foredeck crew to help trim the jib, keeping it flat, and luff tight. The jib boom also acts to control the shape of the jib - luff/leech tension, camber, etc. A jib without a self-tacking jib boom is very difficult to trim using only one radio channel (the other being reserved for the rudder) in most classes.
Basically, (looking down from above) if you move the jib luff to weather (like on an r/c boat) the hull bow will fall off from the wind nearly an equal amount. If you are using a wing, or even just a mainsail on your multihull, you will probably point higher into the wind (closer to the mark) than you would if you added a jib. On my big cat, I was able to sail much higher than other cats that had jibs, and was easily the first to the windward mark - but one we turned downhill, the obvious extra sail area with the jib cats would come close to catching me - if the skipper was working the boat downhill. Too many however tried to “barn-door” their boat dead down wind, and while the distance was less, deep, broad reaching and gybing downwind always paid off - unless ti was blowing so hard it was “survival” downwind. :rolleyes:
Will try to elaborate more if this still doesn’t make sense. Just look at your drawings and the middle boat, if the jib attached at center-line the wind could come closer to the bow letting the boat sail closer to the wind.
Cheers