3/8 BBB or 3/8 G4 HT dilemma

[svbravo]

Good idea, Chris. Would accomplish the same thing as the oversized link, and allows use of random cut ends on the chain.

[chris95040]

Originally Posted by s/v Jedi

The enlarged link is for attaching the anchor shackle, not securing the inboard end. You want the enlarged link at both ends so that you can turn the chain end for end for double life span.

What does an enlarged link give you that you can’t get from just a bow shackle?

[svbravo]

The shackle pin that goes through the chain link doesn't care whether or not it's a bow or standard shackle shape. It's just a pin. Sometimes the bow shape does fit the anchor side better.

[GordMay]

Originally Posted by chris95040

What does an enlarged link give you that you can’t get from just a bow shackle?

The ability to fit a larger shackle, rated commensurate with the chain. Typical shackles generally have a lower rating, than their corresponding chain size.

[rslifkin]

For G4 / G43 chain, a grade B shackle one size up will typically fit (not always for metric chain) and will have a working load rated a bit higher than the chain. For metric G4 chain or for G70 chain, finding a strong enough shackle without an oversize end link is often a problem.

As an example, I've got 5/16" G43 chain on my boat. Rated working load is 3900 lbs. Shackle at the anchor end is a 3/8" Crosby G-209A, rated working load of 2 metric tons or 4409 lbs. Pin fits nicely through the chain links with a little room to spare. The same would apply for 3/8" G43 and a 7/16" grade B shackle.

[chris95040]

Originally Posted by GordMay

The ability to fit a larger shackle, rated commensurate with the chain. Typical shackles generally have a lower rating, than their corresponding chain size.

I believe you, I just still can’t quite understand why. Assume a link of the actual chain affords a particular diameter cylinder to pass through- let’s say 3/8”.

I guess it’s just that a bow shackle with a 3/8” pin is weaker than an oversized link made of 3/8” material?

I still don’t like the oversized link. I’ve had galvanizing wear away on the last few feet of chain (rather, a P.O. did) and I simply cut those links off and moved on with my life. Seems that is made more difficult if a new custom oversized link is required to be fastened... in situ? Or when you folks say oversized link are you referring to something removable?

[Don C L]

OK, I am still trying to figure out why 400' is required to anchor off California!

[noelex 77]

Originally Posted by chris95040

I guess it’s just that a bow shackle with a 3/8” pin is weaker than an oversized link made of 3/8” material?

Generally (although not always) the pin diameter is greater than the diameter of the metal in the shackle itself. Thus a 3/8” shackle will have a pin diameter greater than 3/8” at least with the better shackles.

The more significant problem is that the shackle can be subject to a higher side loading than the chain.This side loading reduces the strength of the shackle. If you do not want the shackle to be the weak link in the system (it is a bit silly to have 300 feet of chain where he final couple of inches is weaker than rest) then the shackle (at least ideally) needs to have a higher SWL (when subject to a side loading) than the chain itself.

Generally for G3 and G4 chain a high quality shackle can generally be found (although this may be specially purchased rather than available at the local chandlery) that will exceed the strength of the chain even allowing for reasonable side loading of the shackle. There is usually no need for larger end links. However, for G7 chain larger end links are typically needed.

You need to do some simple comparisions between the shackle and chain strength rather than just relying on the above rules of thumb.

Overall, making the extra effort and slight extra cost to obtain a high quality shackle (such as a Crosby 209A) is worthwhile, but larger end-links only need to be considered on G7 (and above) chain.

[evm1024]

I use a Crosby G-209A 7/16" shackle in my G70 5/16" chain. I did have to hand fit the pin to the link. Not all pins will fit all links. Slight variations in size allow this to fit.

A shackle with an allow pin like the G-209A are really a requirement for G70 and to a lesser extent G43 chain to keep "balance in life"...