jdoorly wrote:The spreader should bisect the shroud into two equal angles, so that there are equal forces pressing on the mast (i.e. pure compression/no side forces) with the base of the triangle equal to a straight line between the chain plate and the shroud tang. That's 97 degrees from the lower mast to the plane of the spreader.
There are some spreader designs where the hinges at the mast make it substantially impossible to tilt the spreaders up and down. In those cases you are stuck with 90 degrees instead of 97, and need to hope that it's "close enough" so that whatever remaining non-compression loads the spreader receives will be manageable (I've sailed often enough with the spreaders slightly misaligned and it's never caused spreader failure. I found that failure came from incidents during mast raising or lowering (or happened while the mast was down. New spreaders proved no more resistant in those cases than old).
TIM WEBB wrote:... I'd think you'd want the stay to be able to slide freely in the slot so that when the rig is tensioned, it will "find" it's correct place on the spreader end, or more precisely, vice versa, the spreader end will find it's place on the stay? Make any sense?
I think this does make sense. With wires too tight, spreaders can't be adjusted at all, but the distance between top of the shroud and spreader is smaller when there's no tension on the shroud. With wires very loose, the spreaders will slide down and "sag". However, it's easy to push them into position with a paddle before tightening the shrouds. Only problem is in forgetting this step. Whether locked or sliding seems to make no difference in durability - at least in my case where I can trace failure to inadvertent loads on the spreader when the mast was not fully rigged.