Tensioning standing rigging

[Jamie]

I recently helped a friend install his new shrouds and forestay on an old gaff-rigged wooden boat. There are no spreaders on the shrouds, they and the new forestay are all the same diameter as the old ones, 3/8", but are stainless wire rope instead of galvanized. There is also a smaller diameter stainless wire stay to the bowsprit end -- this one was not replaced.

We had her out sailing last Sunday and had no problems, but the lee shroud was very loose, and the foresail on the new stay had a lot of sag (we didn't use the outer stay).

I'm wondering how tight the rigging should be, and how to measure it. Also wondering how best to get equal tension on the two forestays so that both will support a sail properly.

It's not a big boat, only 29 feet. The masthead is about 30 feet from the water.

Any suggestions?

Jamie

[Brion Toss]

Hello,
What construction was the old wire? What construction is the new wire? 3/8" sounds like a large wire for the size boat you are talking about, but you are at least dealing with constructional stretch, and perhaps elastic stretch.
Has anything else changed? Is the hull sound? Did you note leeward shroud tension with the old gang?
Fair leads,
Brion Toss

[Jamie]

I don't know for sure, but I believe the old wire was galvanized wire rope - I'm guessing a fibre core and I'm pretty sure the new stuff has some kind of fibre core. The new rigging was made up for my friend as a favour, and not a lot of information came with it. Very nice, though, spliced and leathered top and bottom. The old wire was pretty rusted with lots of jaggers to catch on everything that came by.

The hull seems to be in good shape. She was out of the water and surveyed in the spring, but the ballast is internal so the surveyor couldn't see the inside low down. Based on what he could see, however, he thought she was okay. No rot found so far.

Nothing else has changed. The boat was bought earlier this year and we didn't try to sail with the old rigging as it was in such poor shape so I don't know how loose the lee shroud would have been then. I'm sure all the rigging was tighter then than now when at rest, but I don't know by how much.

I found a post by Ian McColgin about tensioning an old schooner's shrouds, saying to tighten the windward shroud while watching the lee side. We can try this for the shrouds but I'm still not sure how to equalize the stays.

(BTW Ian, thanks for your reply to my question back in January about running backstays.)

Jamie

[Brion Toss]

Hi again,
Without knowing how the old gang behaved, we need to start at zero, so first assume that there was a lot of constructional stretch in the new, 7x19 wire, and further assume that it might not be completely sailed out of the wire. If this wire has an IWRC core, you'll see about an inch of constructional stretch in thirty feet. If it is a regular core, there'll be even more. So the first thing is to determine what the wire is, so you'll know when it has stabilized.
Next, we know that the new wire is going to have more working (recoverable) stretch more than the old, both because stainless is weaker, and thus more elastic, than galvanized, and because of the construction, which is literally springier. Tune can compensate for some of this, as can massive wire size, which lowers the relative load. We can deal with thal later, but first, find out about that core, so we can run some numbers. Meanwhile, did you track how much you've taken up on the turnbuckles?
Fair leads,
Brion Toss