There IS a true and official sailplan for the M-15; it's never been changed. Tyler- all sails are measured by their LP, which is measured by making a perpendicular off the forestay. We then draw a line parallel to the forestay that goes thru the point where the forward edge of the mast intersects with the imaginary deck crown. Ca'nt be done accurately on a boat because the house is in the way, but easy on a sailplan; we simply take our little pencil and extend the deck crown aft to the proper place. The distance between these two lines is called the LP. A 150% LP is 150% of the measurement if the clew goes thru the 150% line, hi or low. Nothing to do with the foretriangle, and nothing to do with heights. A storm jib is usually in the area of 20 or 30%, and usually the tack is a couple of feet off the deck to reduce the chance of getting wiped out by waves, and the head is not very high, in order to reduce the area and lower the C.E. They do an amazing job considering their area. I have both a storm jib and a heavy weather jib (about 40%, w/o looking it up) and neither have ever been used. The larger of the two is there only in the event that I someday have a 30 knot headwind in a race. If this happens, I'll stomp everyone that doesn't have one! Whooppee! A good thing about storm jibs is that they rarely wear out because they aren't used that much. Usually. They should be made of heavy fabric with lots of patches in the corners. if you have a storm jib and have never hoisted it, better do it to be sure that you have a place to sheet it. On the M-15 the storm jib of the sailplan should sheet to the regular spot, but you'd better check. You can adjust the sheeting by lengthening or shortening the height of the sail; in other words lengthen or shorten the length of the pennnant. -----Original Message----- From: casioqv@usermail.com Sent: Tuesday, August 04, 2015 11:38 AM To: For and about Montgomery Sailboats Subject: Re: M_Boats: Drifter Sail Thanks Dave, I had always assumed that the percentages were area relative to the area of the fore-triangle. Boy was I wrong! I'm surprised the percentages make no account for luff length, since high wind headsails often have a shorter luff than the headstay, and some light air downwind sails have a longer one. My drifter was cut too tall and I had to get the luff cut down, but apparently that didn't reduce it's measured size as a percentage. Whatever sailplan Eliot-Pattison is using for the M15 is way off from what my boat is, I had to cut about 3" off both the main and headsails to make them fit. Surprisingly that doesn't seem to be hurting me any in the races against the newer M15s, but I suspect my boat is also a bit lighter because it has the absolute minimum on all options/features. Tyler '81 M15 #157 Davis, CA ----- Original Message ----- From: "Dave Scobie" <scoobscobie@gmail.com> To: "For and about Montgomery Sailboats" <montgomery_boats@mailman.xmission.com> Sent: Tuesday, August 4, 2015 8:32:25 AM Subject: Re: M_Boats: Drifter Sail Henry: details on the size of a headsail - http://www.jasperandbailey.com/tech/headsails.html