woodscrew wrote;
"so the bow is free to swivel side to side with changing angles of pull."
You present this as if that was an advantage.
Many anchor manufacturers provide a round hole obviously intended for a shackle pin. No shackle end would fit through the hole. They see no advantage to allowing the shackle to rotate or "swivel" as you say. Most shackles called anchor shackles have a larger "bow" as you say w a much larger main shackle ID. The last chain link may be attached to the "bow" (if the pin end of the shackle will fit through the chain link) or a smaller additional shackle is employed. In either event the 2nd shackle or the last chain link will move around the shackle "bow".
In the pic is an example of an extremely large dia anchor shackle on an old flying boat anchor. The shackle bolt of the anchor shackle is permenantly attached to the anchor therefor the intent was obviously that the chain (or line) be attached by the additional shackle. The photo of the anchor is as I bought it.
Most anchor manufacturers now offer their anchor shanks w a slot so the shackle can be attached either way. Over many many decades anchor manufacturers have offered both attachment options so it's impossible to say that one is right. If you put the pin to the chain the chain link will slide to one side loading the shackle unevenly causing a slight weakness. If you put the pin through the hole in the end of the shank the sideways pull on the shackle will be a slight weakness. Either way is not structurally not ideal. But only not ideal when the anchor and rode are not aligned. And the only time when there is high loads on the rode to shank attachment is when the rode and shank are aligned. However w the pin through the chain the shackle will be slightly mis-aligned and the chain link will be over to one side not only when the rode and anchor are mis-aligned but when they are lined up. So the slight disadvantage will always be present unless washers or bushings were employed to center the chain link on the pin.
Looks to me like there's very slight advantage to pin in the shank .. especially if the pin and shank hole were a snug fit. I consider the pin in the shank as shown in post #1 whereas the shackle is of high quality high strength manufacture and of a U shape w no "bow" at all to be the best arrangement. Another advantage to this this arrangement is that the shackle is small w a minimal width so the shank's bottom penetration is not unnecessarily impeded by the anchor shackle.
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Eric
North Western Washington State USA
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