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How a 2:1 halyard works

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Right-e-o all you smarty bummed engineering types, chuck up a nice simple diagram of it please. Don't ask me to, I'm sh*t at things like that.

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Basically you have two times the tension on the halyard acting on the head of the sail, rather than one. So for every kg on the halyard the sail sees twice that. I.e. A 2:1 ratio.

 

Nothing comes for free though so as you pull your halyard 1m, each side only shortens by 0.5m. I.e.a 1:2 ratio on displacement

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On some performance dinghies they rig it the other way, small block in the mast, halyard attached inside, through internal block and out the exit box. The tail comes out the mast and that's what you haul. Double the weight as Chic says but for every 1m of hauling you pull up 2m of sail. Good for super fast hoists. Probably more playing around to set up.

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I diagram of what? The halyard is fixed to the top of the mast, goes down, through a block or something on the head of the sail, up to the masthead sheave, down to the deck.

Need at least 3 times your hoist in length.

Can taper, but be careful if you climb the mast on that halyard

.

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A 2:1 setup also reduces the mast compression induced by the halyard by 25%. Which if you're winching the hell out of a 2:1 code zero halyard like we do on WT, is actually quite a lot of load.

 

Incidentally KM, We're CNC'ing a nice little 2:1 ferrule shackle if you'd like to test one for us. you'd want our 6-8mm version.

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Yeap Mr Clipper, I should have been clearer

I diagram of what?.
This particular bit
A 2:1 setup also reduces the mast compression induced by the halyard by 25%.
Tim W explained it to me once but buggered if I can put it to others as well as he put it to me.

 

So as many say 'WTF? That makes little sense', who can do a nice drawing of how that happens. As they say 'a picture paints a 1000 words' or some crap like that. Someone get all physics or engineering on us.

 

Incidentally KM, We're CNC'ing a nice little 2:1 ferrule shackle if you'd like to test one for us. you'd want our 6-8mm version.
Hell, us old class boats would fall over if the main halyard was twice the weight they are now, besides to have big loads you need big sails, we ain't got big sails. Hence that's why 930 sailors do more with less :thumbup: {what a pile of dribble :lol: :lol: :lol: }

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I thought it reduced the halyard load by 50% in the mast. :think:

 

Luff tension say 200 kgf at 1:1 that would be 200 kgf in the halyard in the mast.

 

Luff tension 200 kgf at 2:1 would be 100 kgf in the halyard.

 

But the overall mast compression load would still be the same.

 

So the only advantage is the small halyard diameter.

 

Even with a halyard lock the mast compression is still the same. :shh: :shh:

 

I will now go back under my rock as you guys flame away. :wave: :wave:

 

 

I think I am incorrect somewhere. :roll: :roll:

 

Of course the mast compression is reduced with a halyard lock by .....

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Tim is right. Reduces by 25%.

 

If the mainsail luff load is 100kg say. Then your main luff is inducing 100kg of compression in the rig downwards.

Likewise a 1:1 halyard is pulling up and around the sheave and back down again- 100kg so the over all load is 200kg. (Halyard load plus sail)

 

If you have a 2:1 quite right it halves the load on the halyard. But the halyard load is only half the compression of the system- so you end up with 100kg mainsail compression, and the halyard compression is half so 50kg. =150kg or 25% less over all compression on the rig.

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