Jeremy, Since the mainsail that came with Griselda when you bought her is a full batten sail with a lot of roach, with the working jib, you will probably be losing closer to 40 square feet of sail area with the sails you are describing. If you compare to the sail area with the 150 Genoa in Griselda's inventory, it is more like 60 square foot less. Those "new" tanbark sails are almost 25% less area than with the working jib and 35% less than with the Genoa which should translate to somewhere around 20 to 30% more wind required for the same light to moderate air performance. When the stock main was changed to the new full batten sail, the difference in light air performance was significant and she pointed noticeably higher going to windward. One comment I have seen on the forums is that the M17 could use a bit more sail area for light air. With Griselda's green hull, I think tanbark sails would look great but, it doesn't seem like the sails you are describing were made to fit the boat. A lot of planning between owner and sail maker went into making Griselda's current sail inventory to maximize performance (full batten main, working jib, high cut yankee jib, storm jib and the existing but seldom used 150) and those sails are like new. We pays our money and makes our choice. Whitebeard Comments based on input from older Bro who sailed Griselda for a long time. -----Original Message----- From: Bowman, Jeremy Sent: Monday, February 14, 2011 3:33 AM To: montgomery_boats@mailman.xmission.com Subject: M_Boats: Sail Area vs. Performance So, I did some calculations to find the difference in sail area between what this site says: http://www.sailritesails.com/ShowAd.aspx?id=5832&sourceid=0 ...and what my new tanbark sails are... Main: Leech 20', Luff 17'2", Foot 7'6". Jib: Leech 14'5", Luff 13', Foot 8'6". I think my new sails come out about 30 square feet smaller than original. How will this affect sail performance? I know I won't have as much power, but how much more wind would I need to reach hull speed? (I tried posting another post with pictures but it is on hold waiting for mod approval). _______________________________________________ http://mailman.xmission.com/cgi-bin/mailman/listinfo/montgomery_boats Remember, there is no privacy on the Internet!