I would advise you to look at Robert Ganier's post in the thread the Dog linked.
I, of course, spent great amounts of time this spring measuring and adjusting to equalize my spreader angles. I erected my mast, as only I can handle an erection, and the damn things were still basically horizontal-where they've apparently been since about 1973. I have them well seized to the shrouds, so am unconcerned about slippage. Furthermore, for all the Cartesian geometry displayed, I see no allusions to the fact that the spreader does not apply it's strain to the mast proportionately angle-wise. My casual observations show that most seem to be closer to horizontal than bisecting the shroud. Whether correct or not, this seems to be the case. In short, I suspect the actual angle is not critical (how accurate can you get it?) and while upwards to a degree is desirable, slippage is intolerable. JMHO, YMMV
08-07-2007 12:11 AM
The spreaders should bisect the angle formed by the shroud at the tip of the spreader. The angle between the shroud and the spreader above the spreader should equal the angle between the shroud and the spreader below the spreader. This will leave them angled upwards slightly.
If the spreader isn't bisecting the angle formed by the shroud, then the shroud can exert a downward torque on the spreader, which it really isn't designed to resist. If the spreader is forced downward, then it will eventually bend and fail... then the mast falls over. This is generally not good and quite expensive. See the following thread about this. LINK
08-07-2007 12:02 AM
Help solve a debate..
My buddy says spreaders should extend perpendicularly from the mast.
I think I have read that they should be slightly above the horizontal. And that the angle that is formed from the shroud wire and spreader should be equal above and below the spreader end.