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Old 07-06-2020, 12:21 PM   #1
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Is my chain undersized?

Marine Trader 44. I live on the hook, so first thing I did was buy a big anchor (85lb Mantus). Boat came with 5/16 chain. Half the chain was rusted junk. I have about 75-100ft that is good, which has been enough because I'm in South Florida and most anchorages are 10ft or less. However I would feel better having at least 150ft (if not 200).

If I buy new chain, the debate is 5/16 bbb vs. spend $400 on new gypsy and upgrade to 3/8 bbb.

If I was a weekend warrior or marina guy, sticking with 5/16 would be a no brainer. But what are your opinions considering my situation?
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Old 07-06-2020, 12:24 PM   #2
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Does your gypsy accept 5/16" g43? If it does, that's what I'd use. It's plenty strong for the boat and won't add weight over what you have now.
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Old 07-06-2020, 12:54 PM   #3
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An 85 lb Mantus is a beast of an anchor and a good choice. But extrapolating from various anchor tests that anchor should hold 5.000 lbs or more in good bottom conditions with 6:1 scope. Your current chain- 5/16 BBB has a maximum working load (MWL) of 1,900 lbs and a breaking strength of 7.600 lbd which is way too low IMO.

5/16 G43 chain has a MWL of 3,900 lbs still too low and 3/8 BBB has a MWL of 2,650 lbs also too low.

Since this is a heavy duty anchor that presumably could carry you through near hurricane strength winds or above I would go with 3/8 G43 chain which has a MWL of 5,400 lbs.

You spent a bunch on a quaility heavy anchor, now complete the system by matching it with heavy chain. Also look at your snubber and chafe protection. I would use a pair of 3/4" nylon three strand rope for snubbers.

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Old 07-06-2020, 01:09 PM   #4
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In my book, the working load of 5/16 g43 is plenty when you consider the boat. The anchor may be able to hold more, but it would be very hard to get that boat to put 3900 lbs of load on the chain, especially with a good snubber.
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Old 07-06-2020, 01:41 PM   #5
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The question should probably be stated as what tensional rating should I use.
So I agree w rslifkin.
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Old 07-06-2020, 01:55 PM   #6
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Interesting that everybody here seems to be recommending HT chain. When I inquired to someone at Miami Cordage about HT chain, he said he "wouldn't touch that stuff with a 10 ft pole". And didnt want to give a reason.
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Old 07-06-2020, 02:05 PM   #7
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I also notice that most commenters are recommending HT to save weight. And nobody thinks I would want to step up to 3/8 chain FOR the weight. Wouldn't heavier chain be beneficial for holding? Seems unnecessary to worry about carrying an extra 75-100bs on a boat this size.
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Old 07-06-2020, 02:38 PM   #8
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Heavier chain is definitely better for holding and I agree that the extra weight should not be a problem for you. I can’t imagine and have never heard a reason not to use HT chain. 3/8 BBB has too low a working load limit, so either 3/8 HT or something larger in BBB. The biggest deal though is going to be finding what works in your windlass. To set everything up right you may need to change the Gypsy to work with a properly sized chain.

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Old 07-06-2020, 08:12 PM   #9
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5/16 would be fine. You’re not going to break the chain. If your windlass would accept HT I would go with that just for peace of mind.
Worry about anchor chain breaking is for folks sitting on their couches, not for folks using their boats.
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Old 07-06-2020, 08:33 PM   #10
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Quote:
Originally Posted by ERTF View Post
I have about 75-100ft that is good,
How much is bad? What is your total length? better to have the correct amount of GOOD chain than 50% of crap rusted stuff.
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Old 07-06-2020, 08:48 PM   #11
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I would sleep better with 3/8" chain. That said, the important thing to understand is shock absorption. While I never heard of anchor chain in good condition parting, I have seen some too small chain stretch and deform. Had to do with anchor in shipwreck and only chain between it and the boat, no shock absorption.

With your stout anchor that will likely not budge, you will want probably several options on snubber based on conditions. The idea is to eliminate shock load so than the chain only sees pulling force. For what you plan to do, I would consider maybe 2 snubbers. One that is smaller with more stretch to slow the boat down and a second one of larger size with limited stretch to to make the final stop. Maybe in that configuration 5/16" chain might be ok.

But, there's no kill like overkill!

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Old 07-06-2020, 09:06 PM   #12
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One thing to bear in mind with hi test chain is once it gets regalvanised, its no longer hi test.
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Old 07-07-2020, 07:23 AM   #13
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I bought 5/16 BBB chain for my windlass and 40 ft boat.

I figured that I'll never get up near the working load except maybe in very very high winds.

If I have to ride through a hurricane and I get beyond the working load, and it deforms ...okay but what's the chances of my anchor even holding up to the breaking load of 7600 lb?

If I do survive all that, I'll just replace the chain.
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Old 07-07-2020, 09:50 AM   #14
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To be clear, I've lived on the boat 18 months already. I run 1/2" dual snubber for cushion, but have a thicker one should I feel I need it. Also, If there's a hurricane I'm going to the mangroves. The only reason I am debating this is because I feel my chain is short and figure I should buy new chain regardless. And I enjoy the ease of mind of being able to drop anchor confidently in a large waterway and not worry about what happens when the wind shifts 180.

I have a Lofrans Tigres windlass. They appear to make different size gypsy's for bbb and ht. I'm very hesitant to buy 5/16 HT chain, because I assume my windlass is bbb and they certainly make 2 different 5/16 gypsy's for a reason. Regardless, if I'm buying a new gypsy, then it's a no brainer to move up to 3/8. And defender appears to sell HT for less than bbb, so i guess the debate is 5/16 bbb vs 3/8 ht. There's really no logical middle ground.
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Old 07-07-2020, 09:54 AM   #15
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I'd get a foot of 5/16" HT and see if it fits your current gypsy. Some windlasses use the same gypsy for both types of 5/16", some have different ones.
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Old 07-07-2020, 10:02 AM   #16
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I'd get a foot of 5/16" HT and see if it fits your current gypsy. Some windlasses use the same gypsy for both types of 5/16", some have different ones.
My windlass already jams constantly without somebody tapping the chain with a bar just right on retrieval (especially under any type of tension), so I'm particularly hesitant to buy an out of spec chain for it. I just doubt I can get a real confident confirmation with 18". But maybe I will contact manufacturer to see if they are the same gypsy with different names.
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Old 07-07-2020, 10:16 AM   #17
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Regarding load: a 44' trawler let's say has a beam and air draft of 15' so 225' frontal area. 1900 lbs constant load will be reached at a bit under 50 knots wind. Surge loads maybe double. That's a squall not a hurricane.

Regarding the gypsy: sounds to me like you already have the wrong one. Or the chain or gypsy are badly stretched/worn. It shouldn't act as you describe. Could it be that your gypsy is actually intended for HT and someone fitted BBB unknowingly?
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Old 07-07-2020, 10:31 AM   #18
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That's if your boat is 15 feet square in the front, mine is pointed at the bow and rounded topsides....that changes things significantly.

I have found most internet guesses wildly inaccurate for calculating load forces on a boat.
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Old 07-07-2020, 10:31 AM   #19
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Regarding load: a 44' trawler let's say has a beam and air draft of 15' so 225' frontal area. 1900 lbs constant load will be reached at a bit under 50 knots wind. Surge loads maybe double. That's a squall not a hurricane.

Regarding the gypsy: sounds to me like you already have the wrong one. Or the chain or gypsy are badly stretched/worn. It shouldn't act as you describe. Could it be that your gypsy is actually intended for HT and someone fitted BBB unknowingly?

I'm thinking the same about the current chain / gypsy match. It's already not right, so getting new of the same and keeping the gypsy is definitely the wrong answer.

As far as load, 1900 lbs seems high in 50 kts of wind from some of the measurements I've seen done. Don't forget to account for wind speed being lower closer to water level. So 50 kts at flybridge height might only be 40 kts 3 feet off the water, meaning the force on the hull is significantly lower.

But in general, I agree that 5/16" BBB is a bit light for this application.
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Old 07-07-2020, 10:40 AM   #20
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I have been using 5/16 BBB chain for the last 20,000 miles of East coast ICW cruising and have been through numerous gusty thunderstorms and the chain is not deformed .

I'm try and NOT anchor out if the weather is predicted to be e severe....but as they say, I have been caught occasionally.

If you are the type to even dare hurricanes at anchor... sure go heavy. If you are like me and are well prepared for 95% of the time.....5/16 BBB chain is probably more than adequate..

I would rather have some extra chain to feed out as snubbers fail/chafe, rather than get to the end of a heavier chain with no extra and have shock loading because I no longer have a few more feet of lighter chain to feed out.

The trouble with these discussions as we all in our minds eye see different scenarios, thus different needs and threats.
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