Tuning standing rigging

by Joe Ozelis ozelis@FNAL.GOV

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[excerpted from the Yacht-L mailing list]

1. Set up headstay so that it's a few turns tighter than hand tight
2. Set up backstay so that it is only hand tight
3. Runners and checkstays off, if you have them
4. Center the mast at the partners by measuring to the chainplates
5. Center the masthead by measuring from the main halyard to the chainplates
6. For starters chock the mast fore/aft at the partners so that it's at max "J"
7. Tighten the cap shrouds, then D1's D2's, etc., so that the mast is straight (sight up the mainsail luff track to do this)
8. Go sailing in 10-14 kts of breeze and sight the rig on each tack. Adjust accordingly to keep the rig on center all the way up. Add backstay tension and check rig straightness with the added compression load. Check headstay sag with max backstay - should be no more than 2-4 " (for a 35' boat) in this wind range. If greater than this, with the backstay on as much as needed to get good mainsail shape, then tighten the headstay. If less than this, loosen it (otherwise your headstay will be too tight to provide proper power in the lighter air - also, most jibs are cut with some headstay sag designed in). If you don't have an adjustable backstay, then do these tests with a moderately tight backstay
9. Pay attention to mainsail shape, especially down low, as the luff curve should be matched to the mast pre-bend... pre bend is adjusted by moving the mast at the step and partners. Make this adjustment if the mainsail is either too full or too flat in the lower third, with respect to the rest of the sail (i.e., the sail is out of balance). If too full, increase pre-bend by moving the mast forward at the partners, aft at the step, and vice versa if too flat.
10. Check helm balance with the main and jib sheeted on for sailing upwind
11. If you have too much weather helm with the mainsail flat but not luffing, jib sheeted max in, and enough backstay on to yield ~ 3" of headstay sag while not turning the main inside out, then you need to rake the rig forward a bit... too little helm (or poor pointing ability) and you need to rake aft. This adjustment is done by tightening or lengthening the headstay a few (3-12) turns at the dock. After doing this, again check headstay sag, mainsail shape, and rig athwartships position in 10-15 kts. If you have added rake, be sure to check that the genoa clew is not to close to the deck or the sheet lead is not too far forward, to be sheeted properly.