add tang for running backstay to existing throughbolt?

[mholmes]

I have a valiant 40 1978. We just redid the rig with 1x19 316 stainless, including the intermediate backstays because we had already ordered the wire and fittings (about which we have had numerous valuable conversations in this forum).

We're going to add 5/16" amsteel blue running backs. I want to know whether I can add a second tang on top of the intermediate's tang using the same throughbolt, and keep BOTH the old intermediates and have running backs too. That way we'll have intermediates for when we're lazy and running backs for serious weather. I don't see why the extra tang on the same bolt would be a problem, but I also don't yet trust my intuition on these matters.

I know what you're going to say: that it's way overdoing it to keep both, and that it negates the benefit of having running backs (to let the boom extend closer to the shrouds). But I also read a quote in the Apprentice that went: "nothing too strong ever broke".

but sharing the one throughbolt for both tangs: ok or not?

much appreciation for all the superb advice,
matt

[Brion Toss]

Hello,
That is correct: nothing too strong ever broke. That is exactly why you don't want to put both stays on one bolt.Consider that the loads will be highest when you are driving to weather. If you are not lazy, you will take up on the runners, but those intermediates will still be loaded, just from tune. You now have more load on the bolt than before. Likewise consider that the runners, if they are outboard, will be pulling on a longer lever arm than before, by the thickness of the intermediate tang. Yet more load. Finally, if you will, consider why you are even raising this question. I don't know why you are asking, but it doesn't sound like it's based so much as in engineering as in something else entirely.
If you must keep both stays, put the runner on its own bolt. The bolt itself is the only cost difference, and you get a distributed redundancy out of the deal.
Finally, consider sailing with those intermediates dead slack, and see if they make even the least bit of difference 3/4 of the time.
Fair leads,
Brion Toss

[mholmes]

brion,
thanks for answering what in retrospect seems to be a dumb question. What you say makes perfect sense.
regards,
matt