How to stop the mainsheet twisting?

[Nostrodamus]

On our boat the main sheet goes through two blocks (top and bottom) behind the cockpit to give a 3:1 purchase on the mainsheet down to the traveller.
The problem I have is that the main sheet between the blocks continually twists numerous times making it harder to pull in and out.
I have untwisted the line, turned the blocks and tried almost everything but it always ends up the same.
Has anyone else encountered this and did you find a solution. I tend to think it is the natural twist in the line causing it.

 

[VicS]

On our boat the main sheet goes through two blocks (top and bottom) behind the cockpit to give a 3:1 purchase on the mainsheet down to the traveller.
The problem I have is that the main sheet between the blocks continually twists numerous times making it harder to pull in and out.
I have untwisted the line, turned the blocks and tried almost everything but it always ends up the same.
Has anyone else encountered this and did you find a solution. I tend to think it is the natural twist in the line causing it.

I assume thees are double blocks (ie two equally sized sheaves side by side) as opposed to fiddle blocks ( ie two sheaves, one smaller than the other, in line with each other)

( but two double blocks will give a 4:1 purchase)

If so there is a speiail way of threading them so that they dont twist. I hav a poor picture scanned from an old PBO below. Not the axes of the two blocks are at right angles to each other.

You should be able to find a better diagram with a bit of Googling or someoen will provide a link to a better one

 

[peter2407]

Try this : http://www.bartonmarine.com/tech-info-triple-mainsheet-vang-block-system-reeving-diagram.asp

 

[Nostrodamus]

Just found this but is it that simple?

https://youtu.be/ejo_i7uBoGg

 

[VicS]

Just found this but is it that simple?

https://youtu.be/ejo_i7uBoGg

No, but it might help. My scan show how its done if you can figure it out .

Peter2704 's post shows it for two triple blocks


This set of diagrams here shows it more clearly than my scan http://www.ehow.co.uk/how_5098217_set-up-double-pulley-system.html#pg=7 The key is rigging it with the axes of the two blocks at right angles to each other

 

[Nostrodamus]

Thanks Vic, I will try it

 

[lw395]

The answer is often to get rid of unnecessary swivels.
Sometimes binding them with tape, cord or cable ties allows them to turn enough, but prevents rotation.
If the top block hangs from a wire strop, that may be the cause. If you add a dyneema lashing to it, you can stop it untwisting under load.

 

[Daydream believer]

Try reversing the mainsheet from time to time

 

[Vegable]

I've got it on mine but my pulleys are vertically orientated not side by side and it's a pain at times. Will try the re coiling method and swopping it end to end.
Thanks for those suggestions
Mike.

 

[homer]

We had this problem and the eventual solution is simple (once you think of it). Just tie the free end of the sheet to anywhere handy. It is then impossible for twists to get into it.

 

[AntarcticPilot]

The Ashley Book of knots has a comprehensive section on threading tackles, and he shows a method that a) eliminates friction between leads of the rope and b) avoids twisting. AFAIR, the principle thing is that the pins of the two blocks are at right angles to each other.

Of course, fiddle blocks avoid the problem entirely by keeping all the leads of the tackle in the same plane.

 

[lw395]

....
Of course, fiddle blocks avoid the problem entirely by keeping all the leads of the tackle in the same plane.

Not necessarily, there is a lot of rope out there with 3-strand cores which want to twist when tension is applied. Some ropes just develop a twist with age or use, these can be improved by re-threading.
Maybe some ropes take a while to recover from being on the drun in the shop?

 

[Woodlouse]

Three strand lines are a bugger for twisting when loaded up and there's not much to do about it.

Another big cause of twisting lines are winches. Every time you load and unload a winch drum you are adding four or five twists into the rope.

 

[ex-Gladys]

Of course, fiddle blocks avoid the problem entirely by keeping all the leads of the tackle in the same plane.

Just replaced my mainsheet system from 4-1 fiddle blocks, and they twisted up badly with braid on braid mainsheet. New system is an Easymatic double ended 3/6-1



It has "stoppers" on the swivels,and works really well....

 

[CAPTAIN FANTASTIC]

There is only one way to avoid twisting; the top block must not be swivel;

 

[tony_lavelle]

I have the same problem. I discourage the twisting by coiling the mainsheet backwards, ie anticlcockwise onto my left hand. This reverses the twisting that occurs from the winch. Trouble is, I have to remember as it's habitual to coil clockwise. I'm talking about braided rope not three-strand stuff by the way.

 

[Mistroma]

I have the same problem. I discourage the twisting by coiling the mainsheet backwards, ie anticlcockwise onto my left hand. This reverses the twisting that occurs from the winch. Trouble is, I have to remember as it's habitual to coil clockwise. I'm talking about braided rope not three-strand stuff by the way.

Interesting, I only remember twists being a problem once soon after launching. Taking the twists out of the sheet solved the problem and I didn't give it another thought.

However, my wife is left handed and so am I. So we do coil braid lines exactly as you suggest. Never thought about the winch introducing a twist in the opposite direction.

 

[Woodlouse]

There is only one way to avoid twisting; the top block must not be swivel;

If either block swivels you risk inducing twists.

 

[vyv_cox]

If either block swivels you risk inducing twists.

My 6:1 mainsheet blocks are a pair of triples with swivels top and bottom. They have not twisted in 15 years. I think the OP problem is due to the rope itself.

 

[Topcat47]

However, my wife is left handed and so am I. So we do coil braid lines exactly as you suggest. Never thought about the winch introducing a twist in the opposite direction.

I never coil ropes on my boat as coiling introduces twists, however, my mainsheet still twists, It's usually just half a turn when I tack or Gybe. I reach out and untwist the block when it's within reach. It's never bothered me. It's always the top block as the lower one is not swivelled.