Option 1: If not sure, build it a bit low then shim it. Touche' has aluminum shims under the mast for exactly that reason.
After final assembly, the mast was a bit low. I got a couple 2 x 4's, placed them on the cabin top, cut another 2 x 4, placed it vertically under a winch on the mast and, with the rig loose, used a truck jack to lift the mast and insert the shims. Option 2: If it ends up too high, you can add a toggle to the forestay. Dennis C. On Sat, Mar 25, 2017 at 2:11 AM, RANDY via CnC-List <[email protected]> wrote: > Listers- > > Seeking your input here. I'm in the middle of the mast step rebuild > project a la http://cncphotoalbum.com/doityourself/maststep/maststep.htm. > Lots of pictures of the project at https://drive.google.com/open?id=0B- > NqAxQ6JxFTSzRLbFo0NDl6U1E. > > I'll be cutting new supports from laminated GPO-3 slabs Saturday night or > Sunday morning. Before installing the new supports, I have to decide on > the elevation of the aft support. Of course I took careful elevation > measurements from the cabin sole before removing the original supports. > But the question is, what was the original shape of the top of the aft > support? > > I believe the middle of Grenadine's aft support, under the mast step > block, was compressed down from its original elevation due to a combination > of weakness in the support and standing rigging tension (especially > backstay). Have a look at the pictures and you can clearly see what I > mean, e.g. https://drive.google.com/open?id=0B-NqAxQ6JxFTLXZuXzd1T1pkR28. > This compression has the effect of pitching the mast step aft, thereby > moving the masthead aft, thereby increasing weather helm (which I've > definitely noticed under enough wind and sail - it was strong under full > main and #2 genoa in 30 kts, not surprisingly). > > However I also believe that the original elevation of the aft support may > have been carefully tuned for helm balance, prior to compression below the > mast step block due to weak wood and standing rigging tension. > > The reason this elevation question matters so much is because, using > trigonometry, I can calculate the distance by which different elevations of > the aft support will move the masthead forward or aft, which in turn will > affect helm balance. Each quarter inch of aft support elevation difference > could move the masthead about three inches I believe. > > The last picture (https://drive.google.com/open?id=0B- > NqAxQ6JxFTU3hRNmZoMUU1MFk) in the Google Drive folder linked above shows > the templates from which I'll cut the new supports, traced from the > original supports removed from Grenadine's bilge. I hypothesize that the > dashed line I drew at the top of the aft support template may have been the > aft support's original elevation. > > I'm halfways tempted to split the difference and cut the new aft support > to have that elevation. Of course, I could be full of crap, because I tune > the mast rake using the stays after all, which probably influences helm > balance more than mast step pitch. And of course I can control the sail > selection and sail trim, which probably influence helm balance more than > mast step pitch. However, for a given sail selection close-hauled, with > neither the backstay nor forestay over-tensioned, the mast step pitch would > certainly influence the masthead position and therefore the combined center > of effort of the sail plan. > > What say ye? Does anyone out there know if the top of the original aft > mast step support on a 30-1 was flat all the way across, or did it come > from the factory with a little elevation drop to tune helm balance? I'll > be committing an assumption about that to a GPO-3 slab with my jigsaw in > the next day or two. > > Thanks in advance, > Randy Stafford > S/V Grenadine > C&C 30-1 #7 > Ken Caryl, CO > > _______________________________________________ > > This list is supported by the generous donations of our members. If you > wish to make a contribution to offset our costs, please go to: > https://www.paypal.me/stumurray > > All Contributions are greatly appreciated! > >
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