tensioning shrouds and stays on fractional rig

[Megunticook]

Last year I replaced standing rigging and had a rigging guy tune everything for me, with me at his elbow to learn. He deliberately overtightened things a bit, explaining that the new wire would stretch with use. The mast had more bend and more backward rake than I wanted, but I deferred to the expert. Things were not bar tight but it was pretty stiff.

This year I tuned it myself (having noted turnbuckle adjustment before unstepping last fall), and the mast has minimal rake now and just a slight bend. I found it tricky minimizing the mast bend, the key seemed to be tightening the lower shrouds.

The forestay is good and tight (will give a couple inches if you push on it with some muscle) backstay feels a little loose at rest, but under sail it tightens right up. I tried tightening the backstay but that just bent the mast more and made the upper shrouds loose (and if I tightened those the backstay loosened up again). I fussed with everything a long while before finding what seemed like a good compromise.

In any case, it's sailing great, but in a stiff breeze (15 knots or more) I notice the leeward upper shroud going slack--not flopping around wildly, but you can clearly see it's no longer under tension (I noticed this especially on one blowy afternoon in East Penobscot bay while reaching in 15-20 knots). A very experienced sailor (he goes out almost daily) says that's just fine, but I've also heard it's not fine.

Thoughts? Anyone have any tips for setting up a fractional rig corrrectly? I've poked around online and opinions are all over the place.

[tjr818]

Carl says:

6.) Tighten every shroud and stay so that they have the correct tension and the mast is stayed plumb with no bends or curves in it. Insert cotter pins in the threaded studs and spread them to prevent them from falling out.

Headstays and backstays should never be taken up so tightly that they will not “give” an inch or so if you pull on them with moderate force.
Upper shrouds should also be tightened equally and have about an inch of “give” to them. Forward lower shrouds should have one to two inches of “give”, and the aft lowers slightly more.
UNDER NO CIRCUMSTANCES TAKE UP THE RIGGING TO BAR TIGHT TENSION. Both the mast and the boat can be severely damaged by excessive tension.
Fine tuning of the rig can be completed after the boat has been sailed, and may have to be done again after the boat has been out in strong winds. When sailing, it is important that the mast remain straight and as nearly in column as possible at all times. While sailing close hauled, sight up the mast track and note any mast curve. Does the mast appear to be falling off to leeward at the top, or does it hook upwind? Repeat this procedure on the opposite tack.
If the masthead is falling off on both tacks, the forward lower shrouds are too tight and the upper shrouds are too loose. If the masthead hooks to windward, the upper shroud is too tight in relation to the lower on the same side. When sailing to windward, the forward lower shrouds bear a greater load than the after lower shrouds; however, the after lower shrouds on the windward side should never be
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loose. All shroud tuning should be done from the leeward side. If the rig seems to be equally balanced when you begin, duplicate every half turn from side to side.

[Jim Walsh]

You may also want to consider the use of a Loos rigging tension gauge. It will take all the guesswork out of a subjective endeavor.