Disadvantages of endless mainsheets?

[Brion Toss]

Originally Posted by Ian McColgin

I think I'm missing something here.

I've used an endless sheet/guy for the spinnaker. You never have very much total extra slack in the sheet/guy as one gets eased as the other's trimmed. This solves the problem of lot's of spagetti rolling about. The big trick is to make it long enough that the sail can be bundled into whatever set and strike place you use.

I've also applied the principle to a main halyard turing it into a halyard/downhaul and eliminating the need to coil the halyard's fall.

But a main sheet, two speed or simply double-ended, involves lots of extra line in the cockpit when close hauled. If it's made truely endless, if your long splices run perfectly through the mainsheet blocks, you're still left with a couple of spills of line. I guess that so long as there's no need to coil, a true double ended rig - no extra purchase on one side, could always be eased from the side with a bigger pile of line, always fed off the top of the heap. If the two sides are asyemtiric advantages, one might easily foresee a time when you'd by trying to ease off the bottom of a pile of sheet.

So, it seems to me that given the massive changes in the amount of line to flake about, a double ended main sheet should remain just that, double ended.

Have I missed something? Perhaps I'm too much a slave to my experience in long boomed traditionally rigged catboats and schooners.

Hi Ian,
All good points, and an ideally set up endless sheet should address all of them.
First, there shouldn't be any more total sheet in the cockpit, if the purchase stays the same. So if you had 6:1 before, you'll have the same total amount of spaghetti with a 3:1 as you will with a 3:/6:1. Very often we reduce the purchase when we make a sheet endless: the blocks are sometimes so much more efficient than the originals that the effective purchase is not reduced; the original purchase might have been excessive; and we often calculate for a 3-speed sheet, with the addition of a small winch.
That said, endless works best when both leads exit on the same side.When you want to let a lot of sheet out, you don't have to worry about pulling from the bottom of the pile, since it's twice as fast to blow both sides at once, and you can control this load, if need be, with the aid of (recommended) ratchets in the deck sheaves. And when you do want to ease or take up one side at a time, in high-load trimming situations, you won't be easing much, plus the nature of the double-braid line, with no coiled-in twists in it, is quite resistant to fouling.
I always try to avoid assymetric configurations,by the way, as they make for lopsided vectors, especially with efficient blocks.
Remember, I'm also an old schooner bum, and I'd never consider putting an endless system on something like the "Adventuress", if only because the weight and mass of the rope could make for problems. Plus, on boats like that, there's often a short "skipper's side" for trimming, and a long "crew side", for massed hauling, so the double-ended configuration can make great sense.
Fair leads,
Brion