There are few
The "Manual on Sail Trim" (I think put out by Sail Magazine) has some sections on the interaction of multi-sail rigs. I'd suggest getting on the web and just doing a Google search on "ketch" or "yawl" too. You might find something helpful. I get the sense from reading many posts on various websites, magazine articles, etc. that sailing a yawl- or ketch-rigged boat is something of an "acquired art." Some general rules apply as different sails dominate depending on the point-of-sail relative to the wind. These multi-mast, multi-sail rigs generally offer good flexibility to adapt to wind & sea conditions. You can play various sails in heavy or light air conditions to achieve controllable drive and a balanced helm. I've crewed on a schooner-rigged boat and recall that it took a few iterations of sail trim to settle in on any point-of-sail -- but then again, once there we were hands-off for a long haul until there was a wind or course change. Here we had the interactions of the jib, jib topsail, staysail, fore sail, main sail, and occasionally the Fisherman or a fore & main topsail. I've been on the helm when the sails weren't trimmed properly, too, and really fought with the boat until they got things balanced. Gybing a 78ft schooner in the dead of night with a full spread of canvas is a real experience! That said, the popularity of a modern Bermuda (Marconi) rigged boat is the simplicity of dealing with one mast & basically two sails that can be reefed to handle various wind and sea conditions. Modern lightweight, strong sails, spars, and rigging basically preclude the need for multi-mast rigs. But there are "traditionalists" who still like them. --RonD
