Round brass thimble strength?

[Brion Toss]

Thanks for the kind words, but in reviewing my previous entry, I note the effects of writing it late at night, at the end of a long day. There was a time when round thimbles were the only type available, even for heavy loads; the ones in sails are a surviving example, in a special context, as are other surviving round thimble or ring applications. And of course no thimble -- and no block-and-tackle -- is the best way to do runners, I think. Just one block on deck, with a good lead to take a continuous, single-part HM runner to the empty weather primary winch. Much more power, instant overhaul and take-up, no blocks banging you in the head, neat cheaper. And no thimbles of any shape needed.
Fair leads,
Brion Toss

[benz]

I am considering runners such as you describe, but have to work out a few issues of proper lead. And I'd have to buy another winch handle--something I've not missed since it went by the board a year ago or so. Do you fear possibly over-tightening the runner with a winch?
Ben

[Brion Toss]

Hi again,
Think about what the runners are meant to do: oppose the pull of the forestay, just as the backstay opposes the pull of the jibstay. If the working load of the forestay is something like 15 to 20% of break in a breeze, some of that load gets taken up by the mast's own stiffness, but most of it is left to the runners. It is possible to flatten the luff of the forestays'l too much, but it ain't easy, and it [/i]is[/i] easy to check the effect by eye. That leaves the most likely failure point to be the deck block and its padeye, so be sure of your scantlings.
Now compare your 40:1 or so winch power with the 4:1 of a typical runner setup. Basically, you can only hope to snub against the pull of the forestay, and that only if you take up in time; you cannot hope actually to flatten that luff. Plus of course, as mentioned before, those blocks are a literal and figurative headache.
Fair leads,
Brion Toss