mast rake is an issue that comes up again and again.  this comes from jerry (in 1989)   From: jerry montgomery Subject: Re: M_Boats: Tuning an M15 Date: 10 Dec 1998 20:57:20 +0000 ----------------------------------- Hi Doug No, No, No!! Leave the 15 rig a little loose. Forestay tension will come from load on the mainsheet, that way, when you ease the mainsheet (light air or a reach) the luff of the jib will relax a little and the sail will become fuller. This is an advantage of a bendy, 3/4 rig. If you pre-load the standing rigging you won't have this advantage. The reason that slack rigging worked on the Windmill, and many other triangle-rigged boats, probably including the 15, is so that on a run or stalled-out broad reach the mast can flop forward which will make the boat go faster. On the wind, the forestay will determine the mast rake, and nearly all well-designed boats will sail better upwind with the mast raked a fair amount. Notice the "well designed"- some boats will pick up a heavy helm before the optimum rake is reached. To simplify, as a generality, boats will sail upwind faster with the rig raked aft, and they will sail off the wind faster with the rig leaning forward slightly. If you can dig up an old copy of PERFORMANCE ADVANCES IN SMALL BOAT RACING by Stuart Walker (1969, W.W. Norton), it will explain this, and a zillion other interesting things. This book was one of my bibles about 30 years ago and things haven't changed much. I only raced the 15 a few times (and against pretty lazy fleets) and don't claim to know the boat that well in terms of speed potential, but I tune boats by playing around with mast rake until I have a light weatherhelm on the wind in light air with the boat heeled a little. Sit way forward and on the lee side. Don't even bother until you get the new sails; it's impossible to tune a boat right with bagged-out sails because no matter what you do the boat won't go upwind. Hope this helps. Jerry       see also other thoughts -   http://msog.org/cfmods/list_archive_results.cfm?first_srch_text=mast%20rake&...   dave scobie M15 #288 - SCRED visit Scred's www-site: http://www.freewebs.com/m15-named-scred   --- On Mon, 8/11/08, kdocter@bellsouth.net <kdocter@bellsouth.net> wrote: From: kdocter@bellsouth.net <kdocter@bellsouth.net> Subject: M_Boats: Proper mast rake for M-15 To: montgomery_boats@mailman.xmission.com Date: Monday, August 11, 2008, 8:46 AM I know that this has been rehashed before but I don't remember hearing the answer that stuck in my head so I am going to ask again. How do you know when your mast is ideally placed? The last four times I've gone out I was becalmed the first three and the fourth was a boomer of a day resulting in a broken rudder handle. I've been reading the recent posts with delight! It ain't just me! So I don't have a good reference point yet of what my speed could or should be. If I level the boat to "zero" degrees of pitch and roll in my driveway, measured off the floor or the seat, wouldn't that give you the reference point to rake the mast? And if so, how much rake? Jerry, I read your post about feeling ashamed [on Lake Michigan?] and tweaking someones mast because they complained the M-15 was too slow. Can you provide some input please? Kendall, Bossier City, LA. #164