Chain size

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Airnet

Airnet

Member
Joined
Nov 13, 2020
Messages
24
Vessel Name
Valhalla
Vessel Make
West Bay
This boat is new to us since September. The anchor chain is 3/8 G3 chain. It was 3/8 G4 from the factory in 1999. We are 75-80k lbs and 64' LOA. The 3/8 G3 chain makes me nervous so new chain has moved to the top of my priority list. I'm thinking upsize to 7/16 G4. IMTRA in Massachusetts sells gypsies for Muir windless. They can special order the 7/16" gypsy with 6 weeks delivery or they have the 1/2" gypsy in stock for $200 less. The 1/2" chain costs about $200 more.
Summery, overall cost of going 300ft of 7/16 vs 1/2" is the same. 300' of 7/16 is about 600 lbs vs 750 lbs for 1/2.
I suppose 3/8 G4 chain is also a much lighter and cheaper option.

The windless is hydraulic and the anchor is a 125lb Mantus M2

Thoughts?

Thanks,
Curt
 
What was it that makes you nervous about the current chain. Does it show signs of stretching, signs of fractures?
I have replaced an anchor or two for no other reason than to calm my perceived problems with the anchor that came with a boat. It is the anchor holding power that will test the chain after all.
 
Normally I would always say that bigger is better. But the WLL of 7/16” G4 is 7,200 lbs and I would doubt you would ever see that load except in near hurricane conditions. Also could your 125# Mantus hold that kind of load.

I guess it all depends on your cruising style and where you anchor.

Davis
 
Going back to the original 3/8 G4 chain is definitely the easiest option with 5200 lb WLL. The current 3/8 G3 chain only has a WLL of 2600 lbs, good to around 30 kts of wind. We run for marinas or cover in storms but 30 kts is not uncommon.
 
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I suspect I'd consider going back to 3/8" G4, and it comes in 200 or 400 drums, so 400' wouldn't hurt. Maybe with another 100-200' of 3/4" 8-plait, depending on depths where you routinely anchor.

And the rope becomes an immediately-available emergency rode if you have to temporarily lose the chain somewhere.

Then I reckon I'd think about it for a while... monitor results... see if anything really needs more fixing.

-Chris
 
Put as much chain as you can. It will give you more flexibility-added weight for holding. More areas to anchor etc. More important is your anchor, which will pull our long before the chain breaks.
 
G30 3/8 has a WLL of 2650lb. Also known as Proof Coil.
G43 3/8 has a WLL of 5400lb. Also known as HT chain.
G70 3/8 has a WLL of 6600lb. Also known as Transport chain.

You may be able to go up in chain grade and stay with 3/8 chain.
 
What water depth do you anchor in?

While I'm firmly in the bigger is better camp, I want to be able to deploy 10:1 when it blows 40+ knots, especially if I'm dealing with associated waves. To realistically use 300' of chain, you're in 20 to 25' of water, factoring in scope above the water and chain on the windlass. If you feel 7:1 is enough in 40+ knots, that's 30 to 35' of depth.

I'm not telling you what you should have, but if you're contemplating 1/2" chain for conditions you might find yourself in, make sure you have enough to get the scope correct for the expected depth.

I almost never anchor in 25'+, so 350' of chain allows me to sleep well at night.

Ted
 
Two more things to consider is how the increased weight affects your trim and the overall size of the chain locker. Many people try to add chain to small lockers only to realize the problems when things go pear shaped.
 
O C Diver said:
What water depth do you anchor in?

I almost never anchor in 25'+,

Ted
Click to expand...

Ted, he is in the PNW so 25' is a rare occurrence. 50' -90' with 3/1 scope is more the norm. I am in the "put your money in an upgraded anchor first, 7/16 or 1/2" second".

I just reread the post, 3/8 G4 would work, Not G3, so chain first
 
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Talking chain size and not chain strength is waste of time. Get the higher grade/strength of chain.
 
I run a boat similar in size to yours in the same general area.
We are truly blessed in that the area is filled with anchoring locations that are generally well protected from wind and/or waves.
Typically there is no need, nor do I desire to anchor at an open roadstead in a 30 knot+ blow. The weather here shows, this is not Mexico.

I would be surprised that the Muir chainwheel (gypsy) would accommodate the use of both 3/8" BBB or G4 sized chain as the G4's links are about 0.130" longer than the BBB's links, based on ACCO's dimensions. My Maxwell 3500 windlass requires a different chain wheel for each. Perhaps yours is different.

I run 3/8" BBB with 400' in the locker and seldom use over 250'. Although I wash the chain with copious amounts fresh water at every retrieval, it's the galvanizing that exhausts itself over time that necessitates chain replacement. 400' allows for a chain flip at about half life of the zinc, thereby almost doubling the replacement interval. Never despite some poor anchoring conditions (nobody's perfect) have I experienced any yielding/deformation of the chain.

If your chain wheel is in good shape and is sized for any particular grade of 3/8"chain, I would use 400' of that grade of chain (if the locker can handle 400') and spend those ugly days on the dock. Regardless of your final grade selection, who wants to spend their time at anchor watch in a blow, anyway?

Now if you are planning a trip to Mexico or live aboard full time, that's different.
 
Side note: when I buy my next anchor chain, I will have them weld a couple links of chain the next size up on both ends. I found that shackles that match the strength of the chain don’t fit. The bolt on the shackle is to thick to go through the link. As mentioned above, I want the bigger links on both ends for when I flip the chain halfway through it’s wear life
 
Mac2 said:
Side note: when I buy my next anchor chain, I will have them weld a couple links of chain the next size up on both ends. I found that shackles that match the strength of the chain don’t fit. The bolt on the shackle is to thick to go through the link. As mentioned above, I want the bigger links on both ends for when I flip the chain halfway through it’s wear life
Click to expand...

Sounds good on paper, but we just bought new chain and I wasn't really able to find "them" who could do that for me... at some kind of reasonable price for the whole deal.

In the past, I'd just used a pair of shackles to get from chain size to anchor size. Not far enough along in my upgrade process to know if I'll have to do that this time or not.

-Chris
 
Mac2 said:
Side note: when I buy my next anchor chain, I will have them weld a couple links of chain the next size up on both ends. I found that shackles that match the strength of the chain don’t fit. The bolt on the shackle is to thick to go through the link. As mentioned above, I want the bigger links on both ends for when I flip the chain halfway through it’s wear life
Click to expand...

For G70 chain that's often an issue. For G43 it shouldn't be. The pin of a grade B shackle 1 size larger than the chain will fit through the link and a grade B of that size should have a working load at least equal to the chain, if not higher. And the working load for shackles is typically rated at a 5:1 safety factor while chain is 3:1 or 4:1, so the shackle will have a higher breaking strength than the chain even at equal working load.
 
ranger58sb said:
Sounds good on paper, but we just bought new chain and I wasn't really able to find "them" who could do that for me... at some kind of reasonable price for the whole deal.

In the past, I'd just used a pair of shackles to get from chain size to anchor size. Not far enough along in my upgrade process to know if I'll have to do that this time or not.

-Chris
Click to expand...
Washington Chain and Supply said they could do it but I’d have to pay for their welder.
 
Mac2 said:
Side note: when I buy my next anchor chain, I will have them weld a couple links of chain the next size up on both ends. I found that shackles that match the strength of the chain don’t fit. The bolt on the shackle is to thick to go through the link. As mentioned above, I want the bigger links on both ends for when I flip the chain halfway through it’s wear life
Click to expand...

ranger58sb said:
In the past, I'd just used a pair of shackles to get from chain size to anchor size. Not far enough along in my upgrade process to know if I'll have to do that this time or not.
Click to expand...


Just a follow-up...

Turns out I was able to use a single 7/16" Crosby G209A shackle... big enough to fit the bow onto the anchor, and the pin fit through the 3/8" G4 chain.

I think the shackle has essentially the same breaking strength as the chain.

-Chris
 
ranger58sb said:
Just a follow-up...

Turns out I was able to use a single 7/16" Crosby G209A shackle... big enough to fit the bow onto the anchor, and the pin fit through the 3/8" G4 chain.

I think the shackle has essentially the same breaking strength as the chain.

-Chris
Click to expand...


Generally for the Crosby G209A (and other grade B shackles) going up a size from the chain (like you did) will give a working load equal to or slightly higher than that of the chain. Breaking strength on the shackle will be stronger than the chain, as it's rated at a more conservative safety factor when they determine the working load.
 
Thanks everyone for the input. I think I'm going to stick with the 3/8 but switch back to the original G4. I've found 400ft delivered to Anacortes for a reasonable price.
 
I would have no hesitation in going with the half inch chain. Is that little extra weight going to upset the balance of your boat?
 
Just curious... but has anybody ever heard of a chain break at anchor? I never have and so it seems very rare. Dragging from a poor set or just overwhelming conditions seems the norm.
 
heysteve said:
Just curious... but has anybody ever heard of a chain break at anchor? I never have and so it seems very rare. Dragging from a poor set or just overwhelming conditions seems the norm.
Click to expand...
I’m guessing it would be from a rusting link if it did break. I had an Ultra anchor with stainless swivel on my last boat. The last link hooked to the swivel lost the galvanizing and started to rust. The next two links were progressively less. Definitely some galvanic corrosion happening. It took approximately 5 years to get to this point.
 
heysteve said:
Just curious... but has anybody ever heard of a chain break at anchor? I never have and so it seems very rare. Dragging from a poor set or just overwhelming conditions seems the norm.
Click to expand...
I, too, have never heard of anyone breaking the chain. Most people buy new for cosmetic reason because of the rust. New chain also settles better in the locker.
 
heysteve said:
Just curious... but has anybody ever heard of a chain break at anchor? I never have and so it seems very rare. Dragging from a poor set or just overwhelming conditions seems the norm.
Click to expand...
I seem to recall a posted video about 10 years ago, probably from YouTube. My fuzzy recollection was a med mooring with stern lines breaking free during a afternoon storm.

Ted
 
If you go by Rocna's sizing guide, you should be well into the 7/16" G4 area.

Anchor Sizing Guide

rocna.com rocna.com
 
I have a mantis anchor along with a mantis swivel the end of the swivel started to rust after 10 years or so. I just replaced the shank generously supplied to me from mantis for a small price. I replaced the stainless shackle with a galvanized shackle. My thought was to make that the sacrificial piece not the anchor Shank
 
I agonized over this issue last winter and settled with 1/2" CROMOX stainless chain with 60 feet of chain and 250 feet of 8 plait 5/8" rode. I have yet to anchor in more than 25 feet of water, typically 10-15 feet so this work well. The nice thing about the SS chain is that it stays clean and since it's kind of "slippery" it lays down well in my anchor locker. I believe it's a 9000 lb load limit. This German SS chain should not be confused with cheap Chineese SS chain with bad welds.
 
sealandsky said:
I agonized over this issue last winter and settled with 1/2" CROMOX stainless chain with 60 feet of chain and 250 feet of 8 plait 5/8" rode. I have yet to anchor in more than 25 feet of water, typically 10-15 feet so this work well. The nice thing about the SS chain is that it stays clean and since it's kind of "slippery" it lays down well in my anchor locker. I believe it's a 9000 lb load limit. This German SS chain should not be confused with cheap Chineese SS chain with bad welds.
Click to expand...
Amazing working load-8,500 lb. What is the chain size compatibility with your gypsy?
 
Bigger chain,,,,bigger gypsy,,,,,equals heavier catenary,,,,,equals more holding power.
 
JimKane said:
Bigger chain,,,,bigger gypsy,,,,,equals heavier catenary,,,,,equals more holding power.
Click to expand...
To some extent, yes. But an extra 20 lbs of anchor will typically gain you far more holding power than an extra 100 lbs of chain. Unless you're in deep water (think 50+ feet) with a lot of very heavy chain, catenary is of limited use. In shallow water you'll pull even fairly heavy chain to almost straight in any decently strong wind.

Personally, based on the data I've seen, my attitude is to size chain based on required strength and don't oversize it for weight purposes. Smaller, stronger chain means you can carry more of it (before weight or locker space becomes an issue) and leave more weight for a big anchor. I'd much rather have 300 feet of 5/16" chain and an 85 lb anchor than 230 feet of 3/8" and a 55 lb anchor (both setups would be within a couple pounds for total weight).
 
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