Doesn't seem logical
Thinking about this, it doesn't make sense. While I'm not a naval architect or physisist, it seems to me that the center of effort of both the main and the jib are both to lewward and forward, with a bulk of the load to lewward. Both sails are pulling the boat, and hence the mast, in essentially the same direction, otherwise the boat would slow down when we raise the second sail. The difference is mostly how that force is applied to the mast. With the main, the force would appear to be spread out over the length of the mast (but if I remeber my college physics from many years ago, can be expressed as a single vector through the center of effort), and the jib would apply its force at a single point approx 3/4 of the way up the mast (where the forstay is attached). It would seem to me that the center of effor of just the main would be somewhere below half way up the mast, as this is where the bulk of the sail is. So, it would follow that the leverage forward and to lewward that the jib is exserting on the mast is actually greater than the leverage exserted on the mast by the main. This may be offset, though, but the greater area of the main.Am I making sense??Rob"Kinship"