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Old 02-24-2018, 08:53 PM   #1
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anchor chain sizing

My 1988 Grand Banks 46 came with 225' of 5/16 HT anchor chain. Chain is 30 years old and ready to be replaced. Even though it hasn't failed in 30 years of use I am a little concerned it is undersized. Doing some internet research other Grand Banks the same size use 3/8 anchor chain. If I replace with 5/16 HT chain I can carry more chain improving anchor scope when I need it. 3/8 chain is stronger but I can carry less meaning less anchor scope in deeper water. Of course 3/8 chain also means more $$$ for larger chain and new windless gypsy.

Thoughts?
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Old 02-24-2018, 09:56 PM   #2
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Originally Posted by jrhodes777 View Post
My 1988 Grand Banks 46 came with 225' of 5/16 HT anchor chain. Chain is 30 years old and ready to be replaced. Even though it hasn't failed in 30 years of use I am a little concerned it is undersized. Doing some internet research other Grand Banks the same size use 3/8 anchor chain. If I replace with 5/16 HT chain I can carry more chain improving anchor scope when I need it. 3/8 chain is stronger but I can carry less meaning less anchor scope in deeper water. Of course 3/8 chain also means more $$$ for larger chain and new windless gypsy.

Thoughts?
Personally, for a boat the size of yours, I'd bite the bullet and go 3/8 chain, which in our language is 10mm, and I have that, and glad of it on my 34 footer. Just sayin'.

However, it would mean a gypsy size change, so it kinda depends on how easy, and how much that costs, I guess. After all. The 5/16 did suffice, one imagines, for the last 30 years. What we don't know however, is how often the boat dragged, and the PO muttered about wishing he had heavier chain..?
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Old 02-24-2018, 10:04 PM   #3
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My 35-foot, 14-ton boat came with 3/8-inch chain. Your 46-footer deserves at least that. Your windlass will probably need modification to accommodate the larger size. Don't see how the increased size couldn't be accommodated with your large boat.
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Old 02-24-2018, 10:12 PM   #4
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On sizable boats you never hear anyone complain about too much chain or to much anchor.
I run 13mm/ 1\2 inch only because they don't make a bigger capstan for the HWC3500.
I would LOVE bigger chain.
Saying that, we went nowhere in 80knots and no indication of stretched links so I guess its fine.

I would say when its time to replace your chain, if you can go a 1/2 inch chain wheel why not?
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Old 02-24-2018, 10:30 PM   #5
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Our 36 has 5/16. 3/8(10mm) makes more sense at 46ft,but the evidence 5/16 works is right before you. I would try to upsize and accept the gypsy expense, if you can get enough 3/8 into the locker. Otherwise,go with the best 5/16 chain you can find.
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Old 02-24-2018, 11:08 PM   #6
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If the boat w it’s 5/16ths chain anchored out a lot and in bad weather too the 5/16ths chain has proven itself.

A lot of pleasureboat skippers go over the top on the size of things. I think a lot of skippers get anchors considerably bigger than is actually needed because they really don’t know what’s necessary. Compare comercial boats and pleasure boats re anchors. A lot of commercial boats have anchors that look small when you’re used to seeing pleasure boats.

On the flip side chain itself makes me slightly nervous. A chain is only as strong as it’s weakest link. How many links are there in 100’ of chain?

I’d go for a little more chain and keep the 5/16” size.
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Old 02-24-2018, 11:48 PM   #7
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The West Marine Advisor* suggests 5/16 HT for a heavy boat up to 48 feet.

The last 30 years seems to back that up.

I guess it comes down to how much sleep will you loose and what's that worth to you. If the current set up has served you well in conditions up to a certain level, keep the same gear, and maybe stand a watch on the rare times conditions exceed that level. Ultimately though, its your wallet and your peace of mind at stake....only you can really answer.




*https://www.westmarine.com/WestAdvis...An-Anchor-Rode
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Old 02-25-2018, 05:27 AM   #8
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"A lot of commercial boats have anchors that look small when you’re used to seeing pleasure boats."

Many commercial boats are fully manned , someone has the watch 24-7.

Sleeping below a small pleasure boat crew does not have this advantage.

An anchor that is larger than "normal'" is only a hassle for the folks with a mechanical windlass.

"Oversized" chain (3/8 is not) will give a smoother ride in modest conditions , and perhaps dodge side to side less.

Sometimes Bigger IS Better, overcoming weight and big windage.
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Old 02-25-2018, 05:41 AM   #9
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I have 5/16 BBB abd sleep like a baby. ...my boats lighter by a bit.

But I have no intentions of anchoring in more than 30 knots of wind. For those short term events like thundetstorms, engine use keeps the strain down.

Look at the strength of the chain versus probable breakout of the anchor.. 5/16HT has a working limit of 3900 pounds with a 4X safety factor to breaking strength. Now consider the holding power of the anchor and your probable anchoring situations.

If I do get caught out and if the anchor holds and if I think I exceeded the WLL, I will gladly replace the chain.
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Old 02-25-2018, 07:57 AM   #10
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I have a 40,000 lb plus boat and am thinking of changing from 3/8's to 5/16's, like the idea of more chain, less weight and 50% greater working load.

3/8 inch G30 BBB (Acco) - 2650 working load, half drum - 200 feet, weight 335 lbs

5/16 inch G40 HT (Acco) - 3900 working load, half drum - 275 feet, weight 285 lbs
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Old 02-25-2018, 08:12 AM   #11
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Before you run out and buy several hundred dollars worth of replacement chain, consider that you might have to replace your windlass if you change the chain size. You have 30 years of (I assume) successful anchoring with what you have so I see no reason to change it.
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Old 02-25-2018, 08:32 AM   #12
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I did a bunch of research on this when doing my retrofit. My boat had 300ft of 3/8 BBB and a 25kg rocna which was way undersized.
What I determined is that BBB has a much lower catastrophic failure rate since steel gets brittle when hardened. I also learned that who makes your chain is the most important thing. The comment about chain only being as good as it’s weakest link is a really important one.
I ended up going with 400ft of new 3/8 BBB but special ordered from a company that both uses American steel but also makes and tests the chain themselves. Paired that with a 55kg Rocna.
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Old 02-25-2018, 10:20 AM   #13
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What are the symptoms of failure that are driving your desire to change?
Age?
Rust?
Wear?
Too short?
Poor fit in the gypsy?
You have stated only the first, which, INHO is not a factor to be considered. Chain doesn't age. It is either the correct material/size/weight/condition for the job or it is not. If it sits in a pile in your locker and never gets used, check it for rust and general condition. If you use it all of the time, check it to see if swapping ends would give it another 30 years of use.

I changed chain shortly after I bought my boat, at about 15 years of age. My chain was leaving rust marks wherever it went and was too short. In the past 25 years with the newer chain I have had no rust left on the deck and am happy with the length.
I have pulled the anchor through a muddy bottom a few times, when carrying the weight of a raft of boats, so maybe bigger anchor would do a better job. I have never considered the chain to be undersized at 5/16.
I would expect to see 5/16 on a GB 46. You should check with other GB 46 owners at your next rendezvous, or ask on the GB forums if you still think yours in undersized.
Can you even get a gypsy for that windlass if you upsize your chain?
Many factors to consider.
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Old 02-25-2018, 12:46 PM   #14
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I have a high windage pilothouse style boat 47í hull length

The OEM was 3/8 BBB. I replaced that with stronger 5/16 HT so that I could carry more chain, at a better strength factor. We carry 550 feet (one full drum) and use a SARCA EXCEL 80 pound anchor.

I have allot of nights at anchor wth this setup, some in some pretty serious winds.

Everything on a boat is a compromise. Choose the chain that makes sense for your boats carrying capability based on the depth you anchor and the scope you want at that depth. 5/16 HT will be fine. My money says that whatever you use to attach your chain (I use a snubber on two cleats) will break long before the chain does.
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Old 02-25-2018, 12:54 PM   #15
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However, it would mean a gypsy size change, so it kinda depends on how easy, and how much that costs, I guess.
On my Maxwell, changing the gypsy is about $600.......If it ain't broke why fix it???
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Old 02-26-2018, 02:58 AM   #16
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On my Maxwell, changing the gypsy is about $600.......If it ain't broke why fix it???
If you are changing chain size you need a new chainwheel
$600 you say? Must be the first time someone in the US has paid double Aust. pricing, usually its us getting raped on everything.
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Old 02-26-2018, 03:03 AM   #17
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The comment about chain only being as good as itís weakest link is a really important one.
I ended up going with 400ft of new 3/8 BBB but special ordered from a company that both uses American steel but also makes and tests the chain themselves. Paired that with a 55kg Rocna.

Were you concerned about Chinese steel and chain?

Your Rocna is a CMP product
They make good quality chain and tested Titan shackles
All made in China.
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Old 02-26-2018, 04:09 AM   #18
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For the OP, replacing using 5/16 HT seems to me to be a very obvious choice. Unless you go HT in 3/8, you won't be any better off, as others have noted. It is more than adequate.

My boat has had 5/16 BBB and a 500lb working load windlass for 36 years. Marginal to undersized in my view, but neither the PO or I have had a problem, so maybe not? Of course, performance was enhanced once I fitted the Sarca Excel No 8 (90lb)

I ordered and paid for a full drum of 5/16 HT a couple of weeks ago as the BBB was a bit rusty. On my way to haulout I anchored up, and the following day had to haul anchor by hand to assist the old windlass. You only do that once. I knew a windlass recondition or replacement was coming soon, but did not think it would be that soon!

So a new windlass being fitted this week. A Muir 3500 with over 50% more working load capacity. I was able to return the 5/16 HT full drum (550') and take a drum 10mm (3/8) instead, normal and not HT. It will be strong enough I'm sure. The full drum of 10mm is only 360', but I'll manage. I might have kept the 5/16 HT but it did not fit the readily available gypsy's from Muir well enough. It was very close, but might have jumped under load. In the longer term, using standard metric sizing is the way to go in this part of the world.
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Old 02-26-2018, 10:54 AM   #19
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If you are changing chain size you need a new chainwheel
$600 you say? Must be the first time someone in the US has paid double Aust. pricing, usually its us getting raped on everything.
They (Maxwell) sent the wrong one the first time and it took a week to get the correct one to Ketchikan Alaska. I had to pay for that one then send back the right one to get a refund.
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Old 02-26-2018, 01:10 PM   #20
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Thanks everyone. I have decided to take replace the existing severely rusted 5/16 HT chain with new 5/16" HT chain but increase the length from 200 to 275 feet. I am figuring since there was good experience with the existing chain. This will allow me to either anchor in deeper water or increase the scope in stormy weather.
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