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With 5/16″ grade 70 chain Peerless chain (WLL 3900 lbs), I was able to use a single forged Titan 3/8″ shackle (WLL 4400 lbs) to connect to a Rocna 27 lb anchor (with a typical slotted shank) avoiding the messy double shackle arrangement. It’s important to note that I chose a FORGED shackle; otherwise, it would have needed a 7/16″ standard shackle to have the proper load rating. But a 7/16″ shackle pin doesn’t fit through the links of a 5/16″ G70 chain. Completely unrelated, I have a spare 7/16″ standard shackle if anyone wants it…
I find the advice in the article confusing. I just purchased a Rocna II 15 to replace my old Danforth lookalike after having some dragging issues in recent seasons on the Chesapeake. I use 1/4 inch G43 chain. Given my use of G43 and a slotted anchor the article seems to say that a second shackle is “necessary.” But then it goes on to say how using a second shackle has significant drawbacks due to the risk of the larger shackle jamming, the smaller shackle crossing the bosses, etc. So which is it? I can attach the 1/4 inch G43 chain to a 5/16 bow shackle with the pin through the chain and the bow through the slot. The bow shackle seems to have good freedom to rotate through the slot and there is no chance that the chain will rotate off the pin. (This, by the way, is how my original anchor was attached.) So the second shackle is not “necessary” to get a fit between the anchor and chain. But perhaps you are suggesting it is necessary to avoid jamming and side loading, despite your warnings that that is still possible with a second shackle. As I said at the start, the advice is confusing. What would you recommend for my setup?
You have a slot. Select a large, quality anchor shackle that will fit in the slot rotate without binding. Then select a high-load shackle that will fit the chain. Ideally, the smaller shackle cannot slide over the bosses on the larger shackle and will stay on the larger shackle’s pin, and the pin will stay in the chain link. No cross-loading of the smaller shackle. Note that the small shackle can be a D-shackle; it will never see a load at an angle. If the larger shackle does cross-load, it should be speced so that it is strong enough to bear the load at 50% of its rating (reduction for cross-loading).
On many anchors–perhaps not yours–a shackle that is large enough to fit around and through the slot will have a pin that is too large to fit through the chain. This is particularly true when people downsize the chain to use G43 or G70, and then up-size the anchor for security. In Ben’s case, it is unusual to use 5/16″ G70 chain with a 27-pound anchor. That’s enough chain for an anchor twic that size, inwhich case his single-shackle solution would probably not work. Ordinarily, 1/4-G43 would be sufficient with that anchor. In your case, 1/4-inch chain with a Rocna 15 sounds right.
The real point of the article is that with the correct shackle, a hole in the anchor shackle, instead of a slot, is perfectly safe and well-proven..