I don't have enough personal experience to talk about double headed rigs, but I've read a bunch of theoretical stuff.
According to "the aeordynamics experts" who have analyzed how sails interact in a sailplan: Adding an innerr foresail doesn't always do what you'd expect. Unless the jibsail and the main are specially designed, you won't get ANY additional drive from the increased sail area. And you may, in fact, get less unless you trim the sails differently than on a sloop rig. Here's a highly technical analysis of the disadvantages and advantages of a double headed rig. It discusses some of the design considerations that affect performance. It's written by the granddaddy of modern sail theory, Arvil Gentry. It's only 4 pages, but it'll take a while to digest all the information. There are lots of graphs and math. If you want to skip the math, go to the last page and read the last few paragraphs to read some conclusions. http://www.arvelgentry.com/magaz/The_Double_Head_Rig.pdf Fair winds, Judy B 1977 Tall Rig #3459, Bijou San Francisco Bay http://www.blumhorst.com/catalina27/catalinahomepage.htm
