Most rigging, on most boats, fits poorly. By that I mean that even if things like pin size, wire size, and leads are properly addressed, we riggers - professional and amateur - too often slip up in matters of length. Sometimes we don't pay attention to potentials for rake or bend, sometimes we get thrown by things like conversions to or from metric lengths, but most often poor fit comes down to a matter of two things: failing to take wire elasticity into account; and failing to correct previous riggers' mistakes.

   The wire elasticity part is fairly easy, once you take into account that it comes in two forms, constructional and elastic (there are other forms, but they shouldn't concern us here). Constructional stretch is just that, the stretch that comes with the yarns in new wire settling into place. For 1x19 stainless, this is about .00021 times the length of the wire. So a 50' wire, of any diameter, can be expected to stretch about 1/8". Not a lot, and not worth worrying about with short wires, but I think it's good practice to take it into account, especially when combined with elastic stretch.

   Elastic stretch, like constructional stretch, also varies with length. But unlike constructional stretch, it also varies with relative load, so the lighter the wire is for a job, and/or the tighter you tune, the more the wire will stretch. Taking a responsibly-designed cruising vessel as an example, an upper shroud might easily be expected to stretch over an inch. Here are the numbers: divide the pounds of expected load by the square of the wire diameter. Take the result and multiply it by 7.79 to the -6th power. That's the reciprocal for 1x19 s.s. So if that same 50' piece happened to be 5/16" diameter, with an expected tuning load of, oh, 18% of the wire's strength, the calculation would look like this: [2,250/097656] x 7.79 exp -6. = .179482. That last number is the percentage of stretch per length, so the last step is to multiply 50' times .00179482, which comes out to about 1 1/16". Add in the 1/8" of constructional stretch and we'll cut 1 3/16" off the wire's tuned length. If we don't, those upper shroud turnbuckles are going to be heading for two-blocked. You can find more information on this in the "Apprentice", or by hiring us for a bit to work through your numbers with you.

   With stretch out of the way, we are left with Other People's Mistakes. Let's say that the previous riggers didn't allow for any kind of stretch. That's why your backstay turnbuckle is bottoming out. So we'll just shorten the new piece by our calculated stretch, right? Wrong. What if those pesky predecessors also misfigured how long the turnbuckle would be at an ideal extension, or how much to deduct for the terminals, or how much to allow for a toggle? The best way to avoid all these questions is to start at zero, which means measuring the total overall length, from the masthead to the chainplate, then deducting very carefully-measured amounts for every component, including stretch. So if our L.O.A. is 51' 4 3/8", we might deduct a sample 1'1" for the turnbuckle, 3" for a toggle, 4 1/8" for the Sta-Loks, and our 1 3/16" deduction for stretch, for a total deduction of 1' 9 5/16". If the L.O.A is right, and if we tune the rig right, the wire will fit, beautifully.

   With a Sta-lok rig, it is possible to put terminals on the top end of every piece, cut everything a couple of feet long, step the mast with the half-done wires on it, and do the bottom ends on deck. Clients often ask us to go this route, assuming that it is easier than the fussier process of measuring and calculating all the lengths, and fabricating everything in the shop. Nothing could be farther from the truth. For one thing, it is a lot easier to make mistakes on deck - it's just a matter of distractions and wire wrestling. Ever try to get all the catenary out of a backstay? Or get an even strain on the shrouds on both sides? And then there's the matter of paying for extra time for the crane operator while you rush around making up some form of temporary rigging. And the elevated consequences of dropping tools. No, doing it on deck is not the easiest way to go, for most people. Traditionally, seizings, and even splices are turned up on deck, but even here, with professionals who can deal with the complications, making up both ends in the loft is always preferable.

   So what do you do? If you have the foresight, get your old rig raked and tuned to perfection before you take it off. Then go aloft and get your L.O.A.'s.

   If, by some miracle, the old rig is perfect as-is, take it off and measure it, but just don't deduct for working elasticity; the wire will shrink up upon removal, and you would just be taking off the stretch length twice. Just deduct for constructional stretch.    And if you measure a perfect-length rig in the boat, once again you will have to deduct for working elasticity.

   Have I covered all the possibilities? Oh, yes, what do you do if you removed the wire before noting turnbuckle extension? Here, if you managed to keep the turnbuckles with their wires, it is often possible to see where the turnbuckles were extended to, by changes in coloring, or thicknesses of dirt. If this is the case, put the turnbuckles back where they were. Figure out what an ideal turnbuckle extension would be. Add or subtract from the wire length, depending on whether the old turnbuckle was longer or shorter than ideal. If a wire had too many or too few toggles, add or subtract accordingly. If you change tangs or chainplates, well, you get the idea.

   Now, if you took all those wires off, didn't keep them with their turnbuckles, and/or didn't note if the rake was right, boy are you in trouble. You can just duplicate the old wires and hope for the best, but the odds are excellent that the old rig was wrong, and you will have devoted inordinate time and expense to duplicating it. This is where the turn-it-up-on-deck option starts looking attractive. But before you go that route, at least consider a little-known alternative: stepping the mast with temporary rigging, making your measurements, and turning both ends up in the shop. You can leave the mast in the boat and install the new pieces one at a time, or, safer yet, take the mast back out after measuring, and re-step after you've dressed it with the new wire.

   And believe it or not, there's even more to this subject, some of which you will find in the new "Apprentice".

   Fair leads,

      Brion Toss