A while back, I issued a challenge to the Michalak discussion group to come up with a calculator or spreadsheet to do the math involved with Jim Michalak's dart method of making sails from polytarp. I used this technique to build my Caprice and ended up with great sails for not much money. I am still using those sails three years later. The only drawback to the system is the math. We had a few submissions, but Tom Hamernik's spreadsheet is the best of the bunch. It is presented here for the first time, so try it and let Tom know how it worked for you.