Originally posted by dbows:
Ok - so to much pre-bend will prevent you from adjusting the forestay. Mast rake tightens the forestay not pre-bending the mast. Pre-Bending the mast makes the mast shorter and forces lower section of the mast forward (think of squeezing a small straw between your fingers it bulges and gets shorter). For kicks loosen your rig to take the prebend out and leave equal pressure on the shrouds (try 25 on Loos) see how tight your forestay is now and then you should see that the backstay is more effective. You may also need to adjust the length of the backstay to make it more/less effective. Then tighten up the rig and watch the forestay so it does not go to slack. If it is too slack then tighten your lowers to remove the pre-bend.
The right amount of sag is based on the cut of your sail, windspeed and halyard tension.
David
#397
[This message has been edited by dbows (edited 05-21-2008).]
[This message has been edited by dbows (edited 05-21-2008).]
Have basically set up as you suggest, with very little pre-bend, 1" - 2". Lowers are at 45 Loos, keeping the middle of the mast aft. Mast step is full forward, mast blocked back in the partners for max rake.
Perhaps I am expecting a straighter headstay than possible. Last night, in 18 knots on a beat, we saw about 3" sag. Our tacking angles were good ~90 deg, so maybe we are OK.
The straw analogy applies more to a masthead rig, where the center of the mast is more free to move forward. Looking at the loading on the mast, and considering the tapered section above the forestay, I don't believe there is much bending going on in the middle. The lowers go up only slightly in tension when I put the backstay full on at the dock, perhaps one Loos #.
