Mike: Thanks for that. I’m not a user of podcasts.
Brion Toss had given his critique of aft-led intermediate shrouds in Chapter 5 of his The Complete Rigger’s Apprentice. Toss started by analysing a Lyle C Hess-designed cutter rig for a 30 foot hull (‘Syrinx’).
"4. Aft-led Intermediates.
"By taking the intermediates off the spreaders and anchoring them a little aft of the mast, you can get them to function for both aft and lateral staying. The drawback to aft-led intermediates is that they don’t do either of their jobs very well. They don’t lead far enough outboard to provide optimum lateral staying, and they don’t lead far enough aft to provide more than trivial aft staying, because with even a minimal aft lead they interfere with boom travel and add to mainsail chafe.
"What is worse, their staying angle is so shallow that they add significant extra compression loads to the mast. So, once again, the mast must be heavier and the staysail smaller.
"I believe that aft intermediates are attractive partly because people don’t realize how ineffective they are, and largely because running backstays can be so very hard to use. As typically configured, tension is supplied by a block-and-tackle, usually 4:1. This configuration must be slacked away and taken up on every tack, a process which involves copious amounts of rope, and has blocks swinging around at head height. And for all this fussing, you get an anemic amount of purchase, not nearly enough to tension the forestay when it matters (i.e., clearing a lee shore in a blow). That is why, in our shop, we run a single-part runner through a single deck block, with a lead to the weather winch. Now you have 40:1 or the like, instead of 4:1, plus runners that set up quickly and slack instantly. No blocks to hit you, no heavy rigging flailing around and chafing the mainsail. The rope is Spectra until just above the block, where a fat piece of Dacron is spliced to it.
“The load on the deck block is higher by about 40 percent than with the older arrangement, owing to the angle departing the block, but this can be dealt with when selecting the block and the anchoring hardware”.
When I read Toss’s critique, I was not convinced. For sure, the intermediates add compressional load to the mast. On Zygote, I reckon the load from the cap shrouds and backstay mean the additional load from the intermediates is not significant.
My other difference from Toss’s recommendation was based on the addition of the runners (plus his suggestion of, for each runner, a deck-mounted block to turn the runner so it can be led fair to a winch, and so avoiding having a 2-part runner with a tackle). We’ve always sailed Z as a short-handed cruiser. Every extra bit of running rigging adds gear and a task - meaning extra duties for a short-handed crew and something else to clutter the working deck (including a potential toe stubber?)…
I therefore judged that the compromise of aft-led intermediates was quite practicable for a cruiser.
For an ocean racer, your judgment might be in favour of runners and the slightly larger staysail they might allow… .