I originally wanted to call this section "Pieces of
string too short to save", after the punch line of
a Maine story about a
notable packrat, who had a box in his attic with
that label on it. The
idea is that you don't throw things away just
because there's no apparent
use for them. In this context, there are a whole
bunch of items that we
don't sell, and ideas that aren't in any of our
books or tapes, and even
things that have nothing to do with rigging at all,
but are too nifty or
unusual or odd to ignore.Back to Fairleads Index
WHY DOUBLE BACKSTAYS ARE EVIL
Rigging should make sense, and by and large, evolution has made sure that it does; nonsensical configurations and details have a way of falling out of favor when they cause the mast to fall out of the boat. There are, however, a few items that persist, despite major flaws in their nature, and the worst of these is (shudder) double backstays.
Nothing the matter with single backstays, or with backstays that fork near deck, if they're done right. But doubles, the kind that run all the way up to the masthead, boy do they get me steamed. They impose unnecessary loads on the mast and hull, constitute extravagant, unproductive weight, windage, and expense, just as far up as you can get it, and they complicate tuning. Also, on ketches and yawls, they prevent the setting of that wonderful driver, the mizzen stays'l. All these vices and more, yet you still see them, even on otherwise intelligently-designed, modern production boats. Why? Because for the less-than-well-thought-out-reasons (LTWTOR's) listed below, many sailors believe that double backstays are a good, worthwhile thing, so builders build them in. So pervasive are these reasons that I despair of making a dent in this configuration's popularity, but here goes a try.
LTWTOR #1 "If one backstay breaks, you still have a good one."
First of all, this seems to assume that one might expect that a backstay is more likely to break than any other wire; this is not the case. But even if it were, double backstays almost always have just enough of an angle to each other that there's a lateral component to their work. This means that the leeward stay will go a little slack. So if the weather stay breaks, the leeward one will not be able to hold the mast stable, nor the jibstay tight. In other words, if one breaks, you still have a good one remaining -- but on the other tack. And even that probably won't be true if you have faux doubles (see below).
LTWTOR #2 "If there's an insulator in one stay, I still have an uncompromised wire, in case an insulator breaks."
This is a variation on #1, with as little merit. It is true that old, or undersized, or badly installed insulators have broken on boats, but this is also true for every other terminal in the rig. Properly done insulators are just as reliable as anything else.
Besides, the "uncompromised" stay will often compromise the efficiency of the antenna formed in the insulated stay, since the two stays are close enough together that the one will provide radio interference with the other.
LTWTOR #3 "They're necessary to counteract jibstay loads, both forward and lateral."
This one sounds compellingly technical, but it just doesn't hold up. For one thing, you've got upper shrouds up there, whose entire reason for existing is to handle lateral loads. For another, much of the jibstay's load is siphoned off by those uppers, leaving less for the backstay(s) to handle. And finally, the angle formed with the mast by the backstay is almost always wider than that of the jibstay, so there's a leverage advantage that further reduces the load on the backstay. This is why, far from needing two backstays, one can often reduce the size of a single backstay.
LTWTOR #4 "A single backstay would get in the way of the swimstep (or self-steering gear, or whatever)."
Now we're getting down to the really flimsy excuses. Going to double backstays to allow for a swimstep (or flagpole, or self-steering gear, or whatever) is like removing your car's windshield to get fresh air inside; there are better ways to accomplish the task. In this case, if a single backstay would preclude the presence of something else at the middle of the transom, it might be possible to move that something to the side a bit. And if that were not practicable, then just move the backstay to the side. Yes, it will be a bit off center, but not so the loading will change appreciably. For example, if you were to move the backstay 1' to the side, on a 45' mast, you'd create a lateral angle with the masthead of about 1 degree. Finally, if there were simply no way to plant the stay anywhere near the middle, you could still go to a forked backstay instead.
Making the conversion to a single or forked backstay is often ridiculously easy. If a single backstay is possible, you need only install a chainplate in the middle of the transom. Since there is usually a lot of linerless space back there, this is usually a cinch. Forked backstays might involve repositioning transom-mounted chainplates, to match the fork angles. Or if the chainplates are internal, it might be a matter of rebending the chainplates. This can often be accomplished in situ. We are currently working on a boat that has twin backstays, but with chainplates that are already angled for forks. That will be an easy conversion.
Occasionally, it is true, there are boats that have to stay with doubles. Maybe the chainplates are unbendable, or the boat has twin jibstays (here, double backstays make sense, but only to the extent that double jibstays do). Another current project has chainplates weirdly far forward, and they are so deeply, heavily glassed into the hull that moving them would be prohibitively difficult and expensive. And we would want to move them, because if they were forked, the steepened inboard-leading angle of forked legs would often make it difficult for the crew to get past the boom. So we had to settle for reducing the diameter of the wires, both of which used to be the same size as the jibstay. You do what you can.
One big irony about many double backstays is that they are already forked. That is, the two legs go to a toggle or linkplate at the masthead, so both legs are hanging on one pin. They look doubled, but that is about it. Converting this setup is a matter of moving the linkplate down towards deck, shortening the legs and adding a pendant.
And some backstays that really are doubled are weaker than singles, either because of a foul-led connection at the masthead, or weak connections, or both. The point is that seeing two backstays on a boat is almost always unnecessarily strong, and often unforgivably weak.
Finally, the danged things just make no sense. You don't see boats with four upper shrouds and eight lowers real often, but that's exactly what one might predict, based on the "logic" of twin backstays. As I said at the beginning, rigging should make sense. Double backstays make sense only if you misunderstand the rig, or if you are a builder hoping to snag some customers with a strong-looking - but actually inferior --- rig.
Next month: Riggerous Exercise
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