What holds the main up on modern race boats?

Ruffles

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Ok, there I am watching the Volvo race on You Tube while lying in the hammock in the garden. And I get to thinking about halyards, the way they stretch and the way they hold the main up on race boats. Is it true that they avoid halyard stretch by 'locking' the main at the head of the mast?

Said hammock is actually suspended between two trees - rather far apart - using an old main halyard. A rigger pointed out to me that it's actually kevlar and almost certainly original to the boat (c1990). Must have cost a fortune; the whole core is an untwisted yellowish fiber which is seemingly impervious to heat. And it stretches not at all. Pity the mantle is knackered.
 

prv

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Is it true that they avoid halyard stretch by 'locking' the main at the head of the mast?

I know that some do. Also some dinghy catamarans.

As well as eliminating stretch, it also reduces the loads on the mast. If you think about it, winching downwards on a halyard that's fixed to a sail that's tacked down near the deck, is essentially the same thing as cranking downwards on the masthead with a 2-part tackle.

Pete
 

flaming

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Yes, the larger ones have halyard locks. As said it can allow you to get away with a smaller section, as the compression loads are halved.
 

Woodlouse

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Not just for the mains, jibs too are often on locks. Main halyard locks are fairly simple and reliable. Jib halyard locks are not.

As well as the aforementioned reduction in compression in the rig it also allows you to have much smaller diameter halyards with a coresponding weight saving.
 

Birdseye

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Not just for the mains, jibs too are often on locks. Main halyard locks are fairly simple and reliable. Jib halyard locks are not.

As well as the aforementioned reduction in compression in the rig it also allows you to have much smaller diameter halyards with a coresponding weight saving.

I suppose in this case you are talking of using the halyard to hoist up the weight of the sail, physically locking at the mast top so there is no load on the halyard and then putting in the luff tension with a downhaul at the foot of the sail. Correct?
 

johnalison

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We were discussing this at my club some while ago and a mate of mine dug out an article describing a halyard lock from many years ago, before the War. I think it was an S&S design and I wouldn't be surprised if those clever chaps invented it.
 

Daydream believer

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Dragons and some squibs have a lock in the mast head.
First pull up locks it. Second pull up releases it
This different to the metal projection that the ring in the mainsail shackle hooks pver on the rotating mast on a dinghy catamaran whereby the sail is hoisted, the mast rotated to push the hook through the ring and the halliard slackened off so the hook takes the weight
 

Woodlouse

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Have you actually seen them. Where is the lock. At the head of the mast or at the point where the head of the main actually comes on the mast
Yes. On big boats the lock is placed along the mast track and engages with one of the head board cars when the sail is fully hoisted. You then ease off the halyard and control luff tension with the cunningham.
 

westernman

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Dragons and some squibs have a lock in the mast head.
First pull up locks it. Second pull up releases it
This different to the metal projection that the ring in the mainsail shackle hooks pver on the rotating mast on a dinghy catamaran whereby the sail is hoisted, the mast rotated to push the hook through the ring and the halliard slackened off so the hook takes the weight

This is what I had on my Hobie Cat FX One.
When new, it was a right pain to get to work - but with use it became at lot easier.
 
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