Hi Robert, I'm the sales rep for Hyde Sails USA who specialized in small boats. A. I, J, P, and E are RIG dimensions, not sail dimensions. B. On a jib, the Luff length, leech length and foot length are linear sail dimensions. With all three, you have an exact defintion of the jibs triangular plan shape and area. C. LP is another linear sail dimension, taken from the luff to the clew. D. % is the ratio of LP to J. We use % to give names to our jibs and genoas. More: 1. What is J? If you use the mast and forestay to define a triangle, J is approximately the distance from the bowstem tack fitting to the front of the mast. (More precisely, J is the linear measurement from a vertical line at the bowstem tack fitting to the vertical line defined by the butt of the mast.) 2. What is LP? There's a linear dimension that sailmakers call "LP", the "length perpendicular" to the luff. If we draw a triangular jib with the luff as the "base", then LP would be the "height". 3. What is the percent LP of a jib? What is its significance? %LP = LP/J. Comments about jibs: LP has some little geometric significance, but not as much as you might assume. You don't know much about the sail if all you know is that it's a 85%. All you can assume is that it's probably pretty small. To know the planform of the jib, you really have to know the luff length, leech length and foot length. Does the luff occupy almost all of the available forestay? That has a direct effect on total area. Sailmakers think about the following things: Is the the clew height high, medium or low (and how that affects twist and the location of the center of effort, as well as visibility)? How does the clew height affect the sails ability to point vs reach? Does the ownner want to favor pointing over reaching or does s/he want a compromise between the two? Finally, the sailmaker has to ask, how will the new sail affect the balance of the helm? Where is the combined COE for the sailplan and how does it relate to the underwater CL? Traditionally, small jibs do not occupy the full forestay. So an jib with an LP = 80% will have an area much less than 80% of the foretriangle. On 100% jibs, the clew will overlap the mast, because the clew location is not on the deck. If it has a moderatly high clew, even a 90% jib may overlap the mast. hope this helps clarify. I'd write more, but I''ve got family and a business to take care of! PS. I have one suit of M15 sails in inventory. Mainsail is loosefooted, has two reefs and sail slides. The jib is a 128% jib. in white 6 oz high modulus dacron. Judy B San Francisco Bay, CA Sailing trailerable sailboats for decades. Big cruisers too. www.blumhorst.com Judy Blumhorst Hyde Sails USA, Northern California judyb@hydesailsUSA.com cell: 925.208.1692 fax: 925.820.2327 skype: judith.blumhorst www.HydeSails.com/NorthAmerica ________________________________ --- On Thu, 8/25/11, Robert Hall <bert.hall@rogers.com> wrote:

Hello All, Does anyone have the exact dimensions for a M15 mainsail, those required to supply to the sailmaker who make the sail? I have the same question concerning the jib. Would also welcome comment on features necessary and/or useful on a new sail.With regard to the jib,is increasing the size a good idea, or do I go with the standard? Has anyone experience with using a drum and swivel jib furling system on the M15 ? Finally what does the term”85% jib “ mean? Thanks. I know the answers are out there. RTH. _______________________________________________ http://mailman.xmission.com/cgi-bin/mailman/listinfo/montgomery_boats

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