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Old 05-03-2016, 01:35 PM   #1
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Proper Chain Link Size for Windlass

I'm replacing my anchor chain and was planning on replacing it with the same size (5/16th) as the existing chain. When looking more closely at the chain in the windlass it seems that with the current sized link, there is some extra room between the link and the windlass teeth. I've attached a photo that hopefully shows the space between the end of the link and the windlass tooth. Does this mean that there is room for the larger 3/8" link? or, is this extra space normal? I'd rather have the larger diameter chain if it will fit the windlass. The windlass is a Muir H1200. I'm attempting to contact the Muir distributor with the number off of the windlass wheel but am interested in what you guys with experience think. Any information/recommendations are very much appreciated. Thanks!
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Old 05-03-2016, 01:48 PM   #2
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That does look a little tight, but I doubt that 3/8" would fit. There are two main types of links that are used in windlasses: BBB and G4 high tensile, and each have different link dimensions. 5/16" G4 has about the same tensile strength as 3/8" BBB.

You currently have G4 probably in 5/16".

Why do you want to go up a size. To fit better or to have more strength. If it is the latter, what is your boat size and displacement. I would be comfortable with 5/16" G4 up to 40' and 25,000 lbs displacement. Beyond that go with 3/8" G4 chain.


Some chain suppliers will sell you a foot of chain so you can check how it fits your windlass, but since you already have 5/16" G4 and I don't think 3/8" G4 will fit, I would stick with what you have.


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Old 05-03-2016, 01:58 PM   #3
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I doubt it will fit. The PO had the wrong gypsy on our windlass when we bought Hobo. It was for 3/8" proof and the chain was 3/8" G4. It jumped.

You can always buy a 1 foot section of the chain your interested in and see if it fits.

Let us know what Muirs says if you contact them.
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Old 05-03-2016, 02:33 PM   #4
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If the chain gypsy is easy to get off take it to whoever you plan on buying the chain from and try different chains to get the best match for it.
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Old 05-03-2016, 02:35 PM   #5
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On a subject I've not seen (recently) raised, how is anchor chain size, BLL and WLL determined for various sized vessels?
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Old 05-03-2016, 03:35 PM   #6
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sunchaser:

That is a great question and there is a lot of confusion behind it. First some terminology:

Chain is rated in WLL- working load limit. It is just what it says, and has a generous, maybe 2-3 times safety factor before it breaks.

Nylon rode is usually rated as its breaking strength. Real world usage should be no more than half of that.

Roughly speaking 5/16" G4 chain has the same real world load limit as 9/16" nylon and that is a very common combination seen on boats up to 40'. Less than 35' you can probably use 1/4" G4 and 7/16" nylon.

There are formulas and charts that will tell you the load on an X foot boat in Y knots of wind, maybe in Chapmans. But these formulas are just for static load. Dynamic load due to seas can be much higher but can be reduced if there is some nylon in the package to absorb shock loads. Nylon will start to stretch at about 1/4 of its breaking strength and elongate up to 50% before it breaks.

So use the above rule of thumb: 1/4" G4 for 30-35', 5/16" G4 for 35-40' and 3/8" G4 for 40-45' and you will be ok.

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Old 05-03-2016, 03:58 PM   #7
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Since (most) of our vessels are attached to an anchor and not a concrete wall the anchor tests show that dragging occurs well below chain WLL in the cases I have looked at. Then the swivel or shackle WLL comes into play getting into the weakest link blather. Then how strong is the cleat or Sampson post yada yada.

I'm sure that all these rode pieces have parted for some, but anchor dragging seems the focus with little in the tables for chain size other than rule of thumb. For our 55K # 48' vessel, we use BBB 3/8"
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Old 05-04-2016, 02:09 AM   #8
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The 5/16 seems to fit well. You haven't managed to break it. Why would you want the extra weight and expense of 3/8 chain?
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Old 05-04-2016, 03:00 AM   #9
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Looking at the photo, it looks like the teeth on the gypsy have worn on the pressure side, giving the impression of slack - upsizing the chain will increase the distance between the centre of each chain link - only by a smidge, but enough to get the teeth and chain loops out of phase and jam/skip. The larger the chain, the less teeth there are on a gypsy - I just upsized our chain - from 8mm to 10mm and there is probably one less tooth in the new gypsy - dia is the same.

BTW, I went from a 15 to a 25 Rocna!!!
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Old 05-04-2016, 09:09 PM   #10
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The gypsy looks worn to me. That doesn't mean a larger size chain will work. It is important that you use the right gypsy for your chain. I recently bought a new gypsy for my Lewmar Tigres windlass. It is for 3/8" G4 chains and cost about $400.
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Old 05-05-2016, 01:15 PM   #11
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Thank you all for the input. We bought this boat, a Meridian 490 Pilothouse, last year so just starting to learn all what I have on the boat. One thing that is puzzling is that from the only piece of paperwork I have for the windlass, it shows I have a H 1200, (Muir Cougar) which would match up to a 40' boat. For a 50' boat, some of the size charts recommend a 3/8'' chain so that is one reason I was looking into the larger size. I also have a 55lb Delta as the anchor, which I'm hoping is not too heavy for the windlass if it is a H1200. I won't be back to the boat until next month so at that time I need to see what is marked on the windlass, if anything. I know is has 'Muir' on the side but can't remember if it also shows 'Cougar' below it. I spoke with Imtra Corp out of New Bedford, MA which I guess is the home office for Muir in North America and he wasn't too much help. He did say to check for a number in the pocket of the gypsy and said I should see a number 133 which should equate to the 5/16th chain. It is possible the previous owner replaced the windlass with a different model and didn't leave the paperwork, so maybe the H1200 paperwork was for the old one. He also said I might not be able to find a serial number on the windlass and to check the paperwork, which in my case won't be of much help. To compound the situation the boatyards around where the boat is docked don't deal a lot with the larger boats, so as suggested above, I'm planning on taking the gypsy wheel to a larger boatyard and they can tell me what I have and how worn it is. Thanks again!!
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Old 05-05-2016, 02:16 PM   #12
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Sammy

Why do you want to replace the chain? Rusty? Does the anchor work OK for you? The reason I'm asking this is because your vessel is designed to plane. Bigger anchor, bigger chain etc just adds weight. Those of us with heavy slow trawlers don't care about the excess weight too much. Take your time, look at the chain and anchor charts and maybe even consider a rope rode with a short chain lead from the anchor.

Are you boating on the rivers? If so, rocks are not as much an issue as compared to those of us in salt water thus a chain rode less essential. Lots of options, you'll figure it out.
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