Attaching pulley to backstay

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rajjes

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Hi,

While the mast is down for rigging replacement I would like to attach a pulley half way along the back stay to rig a dedicated line for the passarelle.

What is the best method of fitting the pulley on 8mm SS wire? It must be tight enough that it does not slip and most importantly does not damage the wire. Is it a matter of lashing or are there some purpose made fittings?

Duncan
 
not sure about pulleys - Barton make shroud cleats that clamp onto 8mm wire - worth checking their web site.
 
Get hold of a S/S wire clamp like this....

BMGZ0173.JPG


...then get a friendly welder to weld a S/S ring onto the flat bit. Attach a block to that to run your passarelle line through. That's what we have.
 
rajjes said:
Hi,

While the mast is down for rigging replacement I would like to attach a pulley half way along the back stay to rig a dedicated line for the passarelle.

What is the best method of fitting the pulley on 8mm SS wire? It must be tight enough that it does not slip and most importantly does not damage the wire. Is it a matter of lashing or are there some purpose made fittings?

Duncan
Click to expand...

To make a backstay tensioning system that pulls the twin backstays together, I attached s/s rings to the backstays using wire rope grips ( http://www.tecni-cable.co.uk/Products/Stainless-Steel-Wire-Rope-Clips-Grips-DIN-741 ) and then shackled the blocks of a tackle to the two rings.
 
Clamp style fittings seem more robust and fit and forget sort of thing, but could they cause a weak spot on the backstay?
 
There must be a possibility of crevice corrosion if you clamp anything onto stainless, particularly 316 grade. Having said that, I put some clamp on plastic cleats on my shrouds for parking halyards without need of anti-frapping lines - just be aware that it's probably a good idea to move them along a bit from time to time and check for deterioration where they were previously. I'm not sure of their strength for an application such as hoisting a passarelle, though.

On a previous boat there were crimped ferrules (copper) on the shrouds to prevent the dreaded spreader droop and one on the backstay, presumbly to prevent the ensign from sliding down. I guess the same concerns about crevice corrosion applies here, but then there were equivalent ferrules on the talurit splices at the end of the stay. I also wonder whether clamping/crimping anything on creates a hard spot and therefore a stress raiser? Hopefully anything like this is occupying a part of the safety margin of the rig's strength!

I guess the ideal solution would be to cut the backstay at the appropriate height and rejoin incorporating a sold stainless plat so you can bolt a block on. I am lucky to be able to do this as I have a split backstay, so the plate is already there at the join.

Rob.
 
A Prusik knot would be ideal, but don't they slide unless under load? As I see it, the problem is keeping it all aloft and ready for use. Assuming the OP would accept a solution that requires setting-up for each use, a Prusik would be fine or else you could simply hoist a block up the backstay with the main halyard - though the stretchy length of rope involved would make the whole rig of the passerelle a little bouncy. If the aim is, on the other hand, to raise the plank to the vertical when not in use, a Prusik know should hold it well - or substitute the topping lift for the halyard.

Rob.
 
Thanks to all for feedback so far.

Knots such as the Prusik would definitely be kinder on the rigging. Not sure of their longevity though as it would need to be quite a thin line - 4 - 6mm and with UV (Malta based) and heavyish loads might not last that long...

Split backstay with a SS plate would be the strongest. Will research this option a bit more.
 
A prusik knot is surely a climbers knot
As this is a sailing forum, might I respectfully point out that a rolling hitch would be the more appropriate knot.
Both knots will slide when not loaded and conversely wont when under load. You just need to tie them the right way round.....
Or are we being infiltrated by alpinistes?
 
rajjes said:
Split backstay with a SS plate would be the strongest. Will research this option a bit more.
Click to expand...

Normally a split backstay has two chain plates, which is what I have and the block is shackled to the eye on the upper single stay. If you have a single backstay you may be able to achieve the same result by by having a new stay made with a break and a plate to take the block inserted. Not sure how that would work if it is masthead rigged and the backstay takes a big load, but worth getting advice from a rigger.
 
I like rolling hitches, but I wouldn't trust one to stay put on slippery stainless wire. Some sort of grippy tape first might be a good idea. Or, taking that idea a bit further, how about assembling a split piece of pipe around the wire to make a mould, then filling it with epoxy? That shouldn't slide.

Pete
 
prv said:
I like rolling hitches, but I wouldn't trust one to stay put on slippery stainless wire.

Pete
Click to expand...

I used a rolling hitch to attach one end of the hammock to the forestay, it never let me down with a bump. I probably weigh a bit less than a gang plank, though.
 
Graham_Wright said:
Can you not use the topping lift instead? Unlikely to be sailing with a passerelle rigged.
Click to expand...

Not very useful unless you have a rigid kicker to keep the boom up. What the OP proposes is quite common - but easier if you have a split backstay as it gives a convenient point to attach the block. Also common to so arrange things that you have the passarelle stowed vertically while sailing. Usually they are folding so not difficult to lash to the pushpit when not in use.
 
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