Alas, no tuning guide. I decided to make my own by setting up the rig at a base tension and then using a Loos gauge and measuring tape from the top of the mast to the transom. Be sure the rake of the mast as measured to the bottom of the transom at base tension is within class specs of 34.9 to 35 ft. I developed a chart by increasing the tension on the upper shrouds (I generally keep the lowers just tight enough to keep the mast straight) and measuring the distance (decreasing) between the top of the mast and the transom. I also measured the increasing tension in the forestay.
I now have a chart of the mast bend (and forestay tension) for my dyform rig under various shroud tensions (important to have calibrated tensioners). Using that I have tested the tensions I use under various wind conditions and then developed the numbers on my shroud tensioners that I use for various predicted winds prior to the race. They are likely to be different for each set up (and even sail loft) but here is what I use:
Base: 1.5
1 to 4 1.75 to 2
4 to 8 knots 2.25 to 2.75
8 to 15 knots 3 to 3.50
Above 15 knots. 3.75 to 4.25
Forte mast generally requires more tension than on the Al rig. Greatest change in bend at lower tension settings and then flattens out. Same with forestay.
I’m sure one could play with lower shroud tension as well but I find these work for my conditions on SF Bay.
Always interested other approaches.
Mike
