I had a bit of an eye opening experience yesterday. I've always set my spreaker settings (2") based on what Yves recommended for my sail and general recommendations from others about diamond wire tension.

I never realized that there was a method to tuning this setting. Yesterday, a friend showed me a thing or two.

we laid the sail on the ground and held the luff taught with some screwdrivers run through the grommets and into the ground. We then ran a thin line from the leading edge of the bolt rope from the top all of the way to the bottom. This helps to see the overall curvature of the sail, as the straight line will traverse through the curvature along the bolt rope and you can measure that distance from the bolt rope to where this line lays.

After taking some measurements, it appears that my sail has a maximum of 4.75" curvature at 14.5' from the top of the sail.

How do I make the mast have this kind of prebend? Does this mean my spreaker rake should be set to 4.75". That sounds pretty severe???

My friend suggested laying the mast across some saw horses, hang some weight off the center and then adjust spreader rake and diamond wire tension until I get the 4.75" gap. Is that the correct thing to do? Any other suggestions?