I hadn't thought much about Gertie's Mast tuning until I replaced the diamond wires and had a couple of discussions with my favorite sail maker. My understanding is that the mast should be as straight as possible and have enough diamond wire tension to prevent the mast from inverting under the load of the spin. I don't recall him suggesting that the mast should have the same prebend as the mains luff.

Gertie's mast WAS set up with the following:
Spreader Rake: 1.75"
Wire Tension: #38 or #39 (Loos Pro gauge) = 700#s - 800#s
Mast Prebend: 1.5"
Sail draft: not so much
Mast Rake: ?
Rig Tension: Good for last Sunday, too tight for this past Tuesday night.

I have now backed off the tension to about #36 = 500# range. (Tension drops off fast).
Mast Prebend: I'll measure tomorrow
Sail draft: Hopefully more than before
Mast Rake: I'll measure tomorrow

Me favorite sail maker also suggested that I do a sail maker bolt rope adjustment. Apparently, the type of ropes that are used as bolt ropes are highly subject to shrinkage. This shrinkage cause wrinkles that the sailor then applies downhaul to remove, often more than is necessary resulting in a flatter sail than desired. He also said that it was very easy and that I could do it myself.


Sorry it took so long to get to this,