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14-11-2020, 05:11
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#31
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Senior Cruiser
Join Date: Mar 2003
Location: Thunder Bay, Ontario - 48-29N x 89-20W
Boat: (Cruiser Living On Dirt)
Posts: 49,362
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Re: Modifying Anchor Shackles
Quote:
Originally Posted by noelex 77
... Whatever you use, make sure it is a name brand with a published load rating, this at least ensures the quality control has been taken seriously. Anchor shackles will experience some side loading that significantly decreases their published strength so it is better to choose a shackle that is stronger than the chain specifications ...
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I would agree, but:
Though I haven't been shackle shopping, for about 20 years; (back then) I don't recall any shackles with higher ratings than the chain they would fit.
Has that changed?
__________________
Gord May
"If you didn't have the time or money to do it right in the first place, when will you get the time/$ to fix it?"
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14-11-2020, 05:47
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#32
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Senior Cruiser
Join Date: Dec 2008
Location: Between Caribbean and Canada
Boat: Murray 33-Chouette & Pape Steelmaid-44-Safara-both steel cutters
Posts: 8,560
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Re: Modifying Anchor Shackles
Quote:
Originally Posted by Muaddib1116
Is that G30 or G40 chain?
https://www.mantusmarine.com/m2-chain-hook/
The bottom of this page has data on their duplex shackles. The 7/16 chain will fit 3/8 chain, but has a lower strength rating than G40 chain. If you want your shackle to be stronger than your chain, you can use their S2 swivel, which uses a 1/2 duplex shackle and has a strength rating above G40 chain. If you have G70 chain, or duplex chain, to make sure the swivel/shackle is not the weakest point in the system, you will have to go up to the S3 swivel that uses the 5/8 shackle. This is what I am doing, but the S3 swivel is quite large, so if you are having problems with shackles clearing your roller, then this is probably not a good option.
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G40 chain.
But its not the chain shackle that is the problem.
I have a Mantus 125 pound anchor.
Then a shackle to attach to the anchor. This is the problem shackle.
Then a shackle to attach to the chain.
Then the chain.
Yes the anchor is oversized. I want an oversized anchor for those times when the bottom is sketchy. And I have been glad ti have it a couple of times. We tend to sail in very different bottoms so matching the anchor to my bottom is not realistic.
So either the chain or the shackle to the chain is the weakest link. The shackle on the anchor can be of less than the highest rating and will still not be the weakest link. Its all good - except that damn pin sticking out to the side that catches.
I have a stainless shackle in stainless that works well. I am backing up with a soft shackle.
SO WHAT DO I WANT??
I am looking for either a galvanized shackle to replace the stainless in event that is a problem
OR
Another stainless shackle to replace the one I found in St Barts, because someday I will need to replace it.
Mantus looks promising, need to check measurements.
Many thanks.
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14-11-2020, 06:20
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#33
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Senior Cruiser
Join Date: Mar 2003
Location: Thunder Bay, Ontario - 48-29N x 89-20W
Boat: (Cruiser Living On Dirt)
Posts: 49,362
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Re: Modifying Anchor Shackles
Quote:
Originally Posted by hpeer
... So either the chain or the shackle to the chain is the weakest link. The shackle on the anchor can be of less than the highest rating and will still not be the weakest link ...
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Indeed.
Every assembly will have a 'weakest link', somewhere.
The key to good engineering, is to ensure that the weakest link is strong enough, for the application, even if other components are vastly over-specified.
__________________
Gord May
"If you didn't have the time or money to do it right in the first place, when will you get the time/$ to fix it?"
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14-11-2020, 06:37
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#34
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Moderator
Join Date: Jul 2007
Boat: Bestevaer.
Posts: 14,678
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Re: Modifying Anchor Shackles
Quote:
Originally Posted by GordMay
Has that changed?
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Generally with the commonly used grade 30 and grade 40 chain it is possible to fit a shackle that is considerably stronger than the chain in straight line pull and still as strong or close to as strong with a pull that is at 90°.
With grade 70 and higher chain it is more difficult and enlarged end links and/or specialised shackles (such as omega links) may be needed.
For example, if we take 10mm chain. This has an inside diameter of 14mm so this is the largest shackle pin that will just fit (if you are lucky). Grade 40 10mm chain has a UTS of around 5t with a SWL of 1.5t. Grade 30 is a little weaker.
A 7/16 inch Crosby 209A has a pin diameter of 12.7mm so should fit although always check, the thickness of the galvanising can modify these numbers slightly. This shackle has a UTS of over 12t with a SWL of 2.7t. Note these are for centralised pull. At 45° the rating drops to around 70% of the above numbers and at 90° around 50%.
This is just one example, but the results will be similar for most of the various sizes of both metric and imperial chain.
It is tedious to check the specifications and then to source a quality shackle, but I think it is worthwhile. It is a little silly to choose such a small and relatively cheap component that is weaker than rest of anchor rode.
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14-11-2020, 14:13
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#35
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Senior Cruiser
Join Date: Dec 2008
Location: Between Caribbean and Canada
Boat: Murray 33-Chouette & Pape Steelmaid-44-Safara-both steel cutters
Posts: 8,560
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Re: Modifying Anchor Shackles
Quote:
Originally Posted by Muaddib1116
Is that G30 or G40 chain?
https://www.mantusmarine.com/m2-chain-hook/
The bottom of this page has data on their duplex shackles. The 7/16 chain will fit 3/8 chain, but has a lower strength rating than G40 chain. If you want your shackle to be stronger than your chain, you can use their S2 swivel, which uses a 1/2 duplex shackle and has a strength rating above G40 chain. If you have G70 chain, or duplex chain, to make sure the swivel/shackle is not the weakest point in the system, you will have to go up to the S3 swivel that uses the 5/8 shackle. This is what I am doing, but the S3 swivel is quite large, so if you are having problems with shackles clearing your roller, then this is probably not a good option.
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I see you use the term “DUPLEX” to describe the shackles.
The object page describes the shackles as 316 stainless.
Can you please clarify what you mean by “duplex”.
———-
I looked at my current SS shackle and it is a Wichard.
The Mantus 5/8” shackle should fit fine and also fit the roller a bit better.
So my system would be:
3/8 G-4 chain to
7/16 HT (Crosby) shackle to
5/8 Mantus shackle to
Anchor.
And THEN the bow roller guides will not snag the mousing wire!!!!!
I hope. 😊
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14-11-2020, 14:21
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#36
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Registered User
Join Date: Aug 2006
Location: Skagit City, WA
Posts: 25,514
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Re: Modifying Anchor Shackles
I often went to high quality stainless 17-4 PH Wichard shackles for that reason and for strength. Not to mention the wider a shackle is the less strong it is by design. I never really saw a detriment to doing it. 17-4 is called SS, but it's mostly iron. And many times stronger than most steel used in shackles.
__________________
"I spent most of my money on Booze, Broads and Boats. The rest I wasted" - Elmore Leonard
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14-11-2020, 14:31
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#37
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Registered User
Join Date: Dec 2019
Location: Boston
Boat: Farr 50 Pilothouse
Posts: 1,349
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Re: Modifying Anchor Shackles
My understanding is that Duplex is 318LN is 2205, which is what Mantus is making it's 7/16, 1/2, and 5/8 shackles out of these days. I've talked to Greg at Mantus, and all the shackles that they are selling in those sizes are now made of Duplex and are marked "2205". On the link I pasted, if you scroll down you'll see a chart showing the UBS and WLL for those shackles.
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14-11-2020, 14:35
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#38
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Registered User
Join Date: Aug 2011
Location: Petersburg, AK
Boat: Outremer 50S
Posts: 4,229
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Re: Modifying Anchor Shackles
Quote:
Originally Posted by hpeer
I see you use the term “DUPLEX” to describe the shackles.
The object page describes the shackles as 316 stainless.
Can you please clarify what you mean by “duplex”.
...
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The page says:
Quote:
The M2 Hook is made from 2205 Duplex...
Shackles are included with the hooks
2205 Duplex Stainless Steel Shackle...
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Duplex stainless, when and where available, has some advantages for saltwater use:
Quote:
Duplex 2205 is a two-phase, ferritic, austenitic 22% chromium, 3% molybdenum, 5 to 6% nickel alloyed stainless steel. It is the most widely used duplex stainless steel grade and is characterized by high yield strength, double that of the standard austenitic stainless steel grades. It also demonstrates good fatigue strength, as well as outstanding resistance to stress corrosion cracking, crevice, pitting, erosion, and general corrosion in severe environments. Source
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14-11-2020, 14:53
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#39
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Senior Cruiser
Join Date: Dec 2008
Location: Between Caribbean and Canada
Boat: Murray 33-Chouette & Pape Steelmaid-44-Safara-both steel cutters
Posts: 8,560
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Re: Modifying Anchor Shackles
Dsanduril and Mauddib,
Thank you for all the info.
The Mantus shackle page makes no mention of duplex but cites strength ratings for 316.
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14-11-2020, 14:58
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#40
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Registered User
Join Date: Dec 2019
Location: Boston
Boat: Farr 50 Pilothouse
Posts: 1,349
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Re: Modifying Anchor Shackles
That's why I linked the M2 Chain Hook page, which does. The have not updated their shackle page.
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14-11-2020, 15:04
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#41
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Registered User
Join Date: Aug 2006
Location: Skagit City, WA
Posts: 25,514
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Re: Modifying Anchor Shackles
Quote:
Originally Posted by hpeer
Dsanduril and Mauddib,
Thank you for all the info.
The Mantus shackle page makes no mention of duplex but cites strength ratings for 316.
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Duplex is roughly twice the strength of 316, Like Nitronic 50
__________________
"I spent most of my money on Booze, Broads and Boats. The rest I wasted" - Elmore Leonard
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15-11-2020, 05:46
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#42
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Senior Cruiser
Join Date: Dec 2008
Location: Between Caribbean and Canada
Boat: Murray 33-Chouette & Pape Steelmaid-44-Safara-both steel cutters
Posts: 8,560
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Re: Modifying Anchor Shackles
Mantus shackles on order.
Thanks guys.
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15-11-2020, 06:03
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#43
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Registered User
Join Date: Dec 2019
Location: Boston
Boat: Farr 50 Pilothouse
Posts: 1,349
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Re: Modifying Anchor Shackles
Sounds good, I hope it works out.
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