Shackles question: D vs Bow ?

[Boo2]

Hi,

What are the advantages of D vs Bow shackles ? When would you choose a Bow and when would you prefer a D shackle ?

Thanks,

Boo2

 

[VicS]

A little bit of Googling comes up with

Each type of shackle has specific uses where it works best. The way that the bow shackle is designed, it is able to handle a variety of types of loads in most directions without too much difficulty. Each shackle is typically rated with a weight limit, and different angled loads will have different ratio of that capacity. For a bow shackle, if they are going to be used intensively it is important to verify that the item has been forged so it is as reliable as possible. Some variations of this shape are simply cast from stainless steel, making them unsuitable for many types of rigging. Bow shackles are often made of stainless steel or titanium. It is important to note that the larger loop does D Shacklesweaken the strength of the overall shackle, but the size also allows for a larger strap.

The D shackle is limited a bit in the way it can handle a load. The small loop at the top can typically handle something heavy, but side loads or racking loads may bend D shackles. For this reason, they are most typically used in bidirectional load situations. Since the loop at the top of the shackle is rather small, the piece is typically capable of handling a significant weight, but always verify restrictions on a particular piece before use.

Otherwise a bow shackle looks prettier

 

[GHA]

Bow's can be used for bridles, with 2 lines attached coming off in a vee. Comercial shax commonly have lines on the body to indicate the maximum angle of the bridle legs. Though confusingly sometimes dee's have the same. But even in that case bridling off a dee is just a pain as the legs never sit right.

 

[southseaian]

Example.
A bow shackle would be best for say tape jack stays. (safety line on deck) The shape of the bow would not distort the tape as much as a D. Distortion suggests weakening.

 

[Deleted member 36384]

Example.
A bow shackle would be best for say tape jack stays. (safety line on deck) The shape of the bow would not distort the tape as much as a D. Distortion suggests weakening.

You use the pin on the tape and head of the shackle at the deck U Bolt (or other securing point) wherever possible to keep the tape flat.

 

[Tim Good]

If it is of any use I am getting Crosby Bow shackles for my bridle to attach to a Jorden Series Drogue. They seem to offer great loading angles and the Alloy versions (as opposed to carbon) by Crosby seem to have greater limits. Tested to 8 times WL as opposed to 5 or 6 on normal ones.

 

[vyv_cox]

If it is of any use I am getting Crosby Bow shackles for my bridle to attach to a Jorden Series Drogue. They seem to offer great loading angles and the Alloy versions (as opposed to carbon) by Crosby seem to have greater limits. Tested to 8 times WL as opposed to 5 or 6 on normal ones.

Not sure I understand this. What do you mean by 'alloy'? The SWL is usually a proportion of the MBL (minimum break load), 4:1 for general use, 6:1 for lifting and hoisting. I have not come across 8:1 before. The usual consequence is that lifting and hoisting shackles, e.g. The coloured pin ones sold by some chandlers, have a lower SWL than similar general-use ones.

 

[salar]

Not sure this is correct but this is what I do - D if the load is single and perpendicular to the pin. Bow if the load is not perpendicular, or if there is more than one eye to attach with a single shackle, hadn't considered the tape option but will add that from now on. If you want a non snag option I like the allen key shackles, I use one to join anchor rope to chain. You can't mouse it but has not come undone yet.

 

[Deleted member 36384]

Not sure this is correct but this is what I do - D if the load is single and perpendicular to the pin. Bow if the load is not perpendicular, or if there is more than one eye to attach with a single shackle, hadn't considered the tape option but will add that from now on. If you want a non snag option I like the allen key shackles, I use one to join anchor rope to chain. You can't mouse it but has not come undone yet.

The tape loop is secured by fastening the pin through the tape. This serves two functions, the eyes of the shackle keep the tip of the tape loop off the deck and reduces wear and tear at this point, the pin keeps the tape flat. Don't use a Bow or the head of a D on the tape loop. It probably does not matter as so many other things can knacker tape jackstays but I would consider the pin in loop to be good practise, my opinion only.

A resultant force on the shackle pin (the bit that is actually securing the load to the structure) is the same irrespective of whether a D or Bow is used, there is a minor difference if the side of the Bow is further offset than the D relative to the pin. The Bow is for double lines, thats really why it exists. The Bow is also good for articulation when the load goes slack as some hard eyes (that are a close fit) can become offset in a D and become cocked when the load comes back on.

Other than that I would not get too hung up on shackle shape as long as it fits and the Working Load Limit is known for straight and angled loads then Bow or D can be suitable choices for the same job.

 

[Tim Good]

Not sure I understand this. What do you mean by 'alloy'? The SWL is usually a proportion of the MBL (minimum break load), 4:1 for general use, 6:1 for lifting and hoisting. I have not come across 8:1 before. The usual consequence is that lifting and hoisting shackles, e.g. The coloured pin ones sold by some chandlers, have a lower SWL than similar general-use ones.

I'm probably confusing matters with my lack of understanding but basically my boat weighs around 18t. Everything in the system for the JSD bridle is designed to take around 50% of boat displacement. I can't fit shackles bigger than those with a 1inch bar due to limitations in the stainless chain plates the shackle attach to. All the ones on the market come out at 6.5t w/l with 5. However see here:

http://www.thecrosbygroup.com/produ.../crosby-209a-alloy-screw-pin-anchor-shackles/

I spoke to Crosby and they produce this shackle to two types. The "alloy" version and the normal version. You'll see the 1 inch bar version there is rated at 9.5t with a 5 times factor. Elsewhere online it, mostly UK sites, the same shackle is listed at 6.5t but with an 8 times factor. After speaking with Crosby they basically said it is the same but the bottom line is that they managed to make that specific shackle stronger for the same size.

Does that make sense? Maybe you can confirm if my reasoning is correct?

 

[GHA]

I spoke to Crosby and they produce this shackle to two types. The "alloy" version and the normal version. You'll see the 1 inch bar version there is rated at 9.5t with a 5 times factor. Elsewhere online it, mostly UK sites, the same shackle is listed at 6.5t but with an 8 times factor. After speaking with Crosby they basically said it is the same but the bottom line is that they managed to make that specific shackle stronger for the same size.

I've wondered before how they could use a different WLL for a 209A (alloy) and a 209. But they are the king of shackles so must know what they are talking about. The different WWL sounds very odd, never seen that before. The WLL is embossed on every shackle, hard to see how anyone could change that. I used to buy 209's by the thousand in a previous job, pretty much industry standard. Though Van Beest green pin are worth looking at as well, the threads and general finish is a little bit better which might help for something spending it's life in a sweaty locker.

 

[vyv_cox]

I managed to look at your link despite the best efforts of Vodafone GR to prevent me! The 209A designation is a quenched and tempered alloy steel whereas presumably the standard 209 is carbon steel. This is similar to the differences in C-links, where the Crosby version is also Q&T whereas most sold by chandlers are carbon steel. The difference in strength is remarkable. Funny how they only say 'alloy' for the pin, I hope they mean alloy steel, also Q&T.

 

[KAL]

As per the quote in Vic S's #2 above. The bow can be loaded in more than a bi-directional way, so good for use when the direction of the pull varies (e.g. On the bow of a boat, or attaching an anchor to a chain, etc.).

 

[rogerthebodger]

Another name for a Bow shackle is an anchor shackle. Anchors should have a slot in the stock so that the shackle body can pass through the stock to allow better articulation and eliminate bending of the pin.