Vectors vs.humans
Hi,
So many variables here. Let's start with how the spreaders contact the spreader bases. It appears that the spreader rake is not the same as the spreader tenon rake, with the latter being greater. Hence the wear on the forward edge. Theoretically, as the mast bends forward the two surfaces will line up, but this is just another way of saying that the spreaders and their bases are only aligned at one state of tune. And we don't even know if, when they are aligned, we will have the bend we want.
Next, the spreaders, their bases, and the upper shroud chainplates must all be in alignment; if the chainplates are too far forward, no amount of tension will induce mast bend. If you sight up each upper, the wire should take a fairly straight course from deck to masthead, in the plane that the spreader is in. If it doesn't, then either the spreader angle is wrong, the chainplate location is wrong, or both.
Finally, relative jibstay and backstay length and tension will be a major factor. If the jibstay is too short and/or the backstay too loose, for instance, the top of the mast will want to stay forward. What kind of tuning numbers are you getting?
Next, lower shroud tune could be fighting the spreaders. I believe that your boat, like the majority of sailboats, the forward lower has a smaller fore-and-aft angle than the aft lower. If this is so, then even tension on the wires will result in the middle of the mast going aft, not forward.
Getting back to those spreaders, the damage you are seeing is not a good thing. Once you have the other variables sorted out, see about bushing the clevis pin holes, and re-shaping the inboard edges.
Fair leads,
Brion Toss
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