Replacing a clevis pin with a shackle

Sea-Fever

Sea-Fever

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I am considering replacing the clevis pin from the baby stay deck attachment with a shackle of similar diameter, stainless obviously so I can later thread a 25mm webbing jackstay through the shackle.

Does anyone have a view on the relative strength of a shackle pin vs clevis pin???

If they are the same material I'm hoping they would withstand similar shear forces unless there is some difference in manufacture process??

Thanks.

Dan.
 
I expect that a stainless steel clevis pin will be made of tougher stuff than an ordinary s/s shackle, but shackles are not all the same, and indeed some shackles have clevis pins! May I suggest an hour's perusal of the Wichard and Harken catalogues? I'd be very careful to get the diameter right....
 
Chainplates are designed to take the loads the rig puts on them. May not be particularly strong in the random directions a jackstay might pull. I'd be very cautious about it, I could introduce you to people who would be very rude about the idea.
 
A shackle wide enough to comfortably accomodate a 25mm jackstay is likely to have a pin much longer than the clevis pin it replaces. I would not like that arrangement .

Also, the deck fitting will be designed to withstand an upward load. How is it likely to react to a sideway wrenching load as would occur if a heavy person goes over the side, and is dragged along by his lifeline?

Not having any means of calculating such loading, I would be inclined to play safe and install a separate attachment point for the safety jackstays. Or, even better, two.
 
The breaking strain of a shackle is also applicable only with a direct pull. i.e. you get a fraction of the strength if you attach your jackstay to the side of the shackle.
 
lw395 said:
Chainplates are designed to take the loads the rig puts on them. May not be particularly strong in the random directions a jackstay might pull. I'd be very cautious about it, I could introduce you to people who would be very rude about the idea.
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Another good point. Intuition tells me the weakest direction for the deck attachment would be vertically up but you're right that that it is not designed for lateral pulls and I'm only guessing.
 
Poignard said:
A shackle wide enough to comfortably accomodate a 25mm jackstay is likely to have a pin much longer than the clevis pin it replaces. I would not like that arrangement .

Also, the deck fitting will be designed to withstand an upward load. How is it likely to react to a sideway wrenching load as would occur if a heavy person goes over the side, and is dragged along by his lifeline?

Not having any means of calculating such loading, I would be inclined to play safe and install a separate attachment point for the safety jackstays. Or, even better, two.
Click to expand...

Yes...I hadn't considered the leverage a wide shackle would put on the fitting under a lateral load....the result of which is unknown.

Damn it.....you lot are full of good advice.

I was hoping to avoid a) drilling holes in the deck and b) attaching to the bow cleats (as I was trying to avoid running the jackstay near the toerail)
 
Fit D rings in the places you need them, of the right size, and seal the deck with butyl tape. Backing plates needed in addition to penny washers, perhaps plywood, I've seen plastic chopping board pieces of appropriate thickness used in this context. I guess they won't rot if there is water ingress over time.
 
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Hey, Ganter.. Bloke askes a question 'cos he want to know. Better that, than be an idiot by NOT asking. This the bit of the forum where people ask questions of people who know a bit more than they do.
 
DownWest said:
Hey, Ganter.. Bloke askes a question 'cos he want to know. Better that, than be an idiot by NOT asking. This the bit of the forum where people ask questions of people who know a bit more than they do.
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You're right DownWest,
I just don't want this guy to do this.
And you're right. This is a useful exchange.

I apologise for my language - I've been sailing longer than I care to remember and Jacks and Rigs are always kept independent of one another for just the reasons stated.

You just get some suggestions that rile you and you think - "No, definitely do not do that."
 
I would question the idea of fitting jack stays to the chain plate. A jack stay is to provide an attachment for a harness to keep a crew on board. A jack stay at the outside of the deck will enable a person to go overboard even though still attached. Not a good situation. IMHO opinion a jack stay should be located well in board so that a person has some freedom of movement on the tether but not enough to let him go over the side. Of course if he is moving to the bow he would have to have 2 tethers so he could get out around the stays without being at any time disconnected. ol'will
 
In principle the idea of having a jackstay well inboard (ie near the babystay) rather than running along the outer part of the sidedeck is good. However as others have said actually attaching it to the babystay chainplate is not good.
 
There are problems with that approach. If your on port side and attached to a jackstay on starboard, the mast for example will impede you forward progress.
Poignard said:
Isn't it better to attach your safety line to the uphill jackstay?

In which case the nearer they are to the rail, the better.
Click to expand...
 
I've replaced a clevis pin with a shackle purely to hold a halyard out of the way whilst sailing. The shackle pin was the same diameter and the 'jaws' of the shackle just fitted. The rigger was more than happy with this set up. I would be reluctant though to use the shackle for anything else.
 
ghostlymoron said:
There are problems with that approach. If your on port side and attached to a jackstay on starboard, the mast for example will impede you forward progress.
Click to expand...

When I go forward, and feel it necessary to clip on, I use the windward (uphill) jackstay. When I get to the foredeck I remain attached to the windward jackstay.
 
RJJ said:
The breaking strain of a shackle is also applicable only with a direct pull. i.e. you get a fraction of the strength if you attach your jackstay to the side of the shackle.
Click to expand...

Specifically:

Manufacturers of good quality galvanised shackles all state that shackles loaded at 90 degrees will have a WLL reduction of 50% (and 75%) if loaded at 45 degrees. I have tested for this and it is correct.

Stainless shackles will be different as they have a low yield and deform easily. In testing at 90 degrees they deform, which I might term as failing (but they do not actually break) to such an extent they are unusable at tensions much less than 50% of quoted WLL.

Shackles are designed to work in a straight line pull.

Jonathan
 
Poignard said:
Isn't it better to attach your safety line to the uphill jackstay?

In which case the nearer they are to the rail, the better.
Click to expand...

If you are going forward you should be go on the uphill side of the boat anyway so you will be using the uphill jackstay.

If you always use the uphill side you are also IMHO less likely to go overboard.

If the sea is choppy I always crawl to keep my CofG as low as possible.
 
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