Sounds like a good plan. It won't take much to hold that plate, as it's just a shim. Just make sure the hardware you use won't interfere with the mast base (bolts sticking out and such). In fact, the extra hardware may be useful down the road for attaching a block, like for a spinnaker halyard. Big boats almost always have a series of connection points on each side at the base of the mast for just such a thing, in fact.Globalhobo wrote:We are actually having an 1/8" plate bent at 90 degree angles on both sides and we'll through- bolt them to the angles. It will sit on the deck and provide a place for the base plate to land but will be easily removed so we can get to the db.
I don't know what the rake on the M boats is supposed to be, and the manual available on this site shows a diagonal measurement rather than an angle to the water line (the text refers to using a level to establish plumb, but the diagram shows geometry independent of boat level or mast plumbGlobalhobo wrote:Do you have any random thoughts on compensating the rake and rigging due to the 1" difference and the plate under? Just drop the plumb Bob and try to get it 4" and tighten rigging accordingly, like Norco said, I suppose?
), so all I would suggest is going with what other owners of that model have found to be satisfactory, like Norca. Adding 1/8" shim to a 5" footprint will tilt the mast about 1.4 degrees aft. My boat, by contrast, is supposed to have 4 degrees of rake, which is giant (and I don't have nearly that much).But having the mast forward an inch won't change the rigging adjustment very much; the shrouds will be a little longer, and the forestay a little shorter, and should be well within the range of the adjusters and forestay turnbuckle. Due to the shallow angle of the forestay, moving the mast forward 1" results in about 1/2" shorter forestay, keeping the mast rake the same. Moving the mast base forward 1" but not changing the forestay length changes the mast rake about .25 deg.
In other words, I'd do what you're planning, and just tune the rig as if everything is everything.
but that it really depends on what our boat does - so we just need to quit fretting and get it in the water (we hope to do that as soon as our plate is made). The 18" starting point was a huge relief to me because we tried tightening the forestay a TON (no more adjustment left) and could only get it to about 8". Phew!
mast works out to just under 23-1/2" offset, and that's with a shorter 28 ft mast. It's also very noticeable in a marina, where it's raked far more than other sailboats, though I've straightened mine up a bit (to about 2.5 degrees) to reduce the tendency to round up, which may have been part of the original reasoning for specifying so much rake. 