Anyone with personal experience downsizing anchor chain with G70 or 318LN

[nfbr]

It looks like g70 would is the same strength as g40 in a size down

Has anyone downsized? Any personal feedback?

Basically 1/2” BBB = 3/8 G43 = 5/16 G70

Thats a big weight saving that can be added to the anchor for better holding.

[noelex 77]

Yes we have done this and then gone back to G40.

Despite our decision to change back to G40, G70 is option worth considering especially for a high performance catamaran where weight is so critical. The weight savings are substantial. The strength (when you go down one size) is essentially the same as G40 so this is not a concern. However be careful comparing the strength of BBB to G43. Much of the quoted difference is due to a reduced safety factor for G43 rather than a real improvement caused by the change in steel from G30 to G40.

There are some drawbacks of G70. The first is that the lower chain weight reduces the setting performance of the anchor. Modern anchors set so well in most substrates that this is not a great problem, but it does reduce the performance in poor substrates, which is where anchor performance can be critical. Much of this can be made up if you put some of the weight savings into increasing the anchor size, but it is a factor to keep in mind. The second drawback is the chain galvanising has a shorter life. This appears to mostly related to lighter chain moving more, especially rolling around on the seabed and hence causing more abrasion on the zinc. As there is less availability of G70 chain, with this shorter life you need to plan for replacement carefully, especially in remote locations. A lighter rode will cause the boat to swing to wind shifts differently from neighbours using heavier chain. The difference is not great for a typical monohull but this is more of an issue for a lightweight catamaran.

These drawbacks need to weighed up against the advantage of the substantial weight savings.

[Tsuru]

Our 44’ 16 ton boat came with 300’ 5/16” G7. I didn’t ask the previous owner but suspected it was primarily to reduce weight in the bow. In use it doesn’t act any different that other chain and has proven reliable. Also the Galvanizing has held up wel (note that this may be due to the substrate we anchor inl.
My only issue is that it is difficult getting appropriate hardware for the anchor to chain connection. For example if I was using 3/8” chain I’d probably connect the anchor with 2, 1/2” Crosby shackles. I don’t have the specs in front of me but they would be the same strength or greater than the chain. The 1/2” shackle will not fit 5/16” and 3/8” that will fit has a slightly lower working strength than the G7 chain. I’ve solved this by using a Kong r swivel that is rated the same as the G7 chain. Being a simple guy I’d prefer to use back to back shackles but the Kong swivel has proven reliable. We’re using a Rocna 33 as a Bower, which seems about right.