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06-10-2021, 14:45
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#1
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Registered User
Join Date: Aug 2019
Location: Quebec
Boat: Cape Dory 30c
Posts: 154
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Scope, All Chain Rode and Breaking Strength
Now that Galvanized G70 is available as anchor chain I am wondering if 350' of 1/4" G70 makes better sense than 200' of 5/16" BBB or HT. The breaking strengths are 9650lbs, 7600lbs and 11600lbs, respectively. So based on total weight in the bow of a 30' 9000 lb displacement boat would be in the same order: 231lbs/350'/1/4"G70 - 231lbs/210'/5/16"BBB AND 5/16" HT.
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06-10-2021, 15:16
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#2
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Moderator
Join Date: Feb 2010
Location: La Ciudad de la Misión Didacus de Alcalá en Alta California, Virreinato de Nueva España
Boat: Cal 20
Posts: 20,489
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Re: Scope, All Chain Rode and Breaking Strength
Per ABYC anchor load chart, 60kt wind loads for a boat your length will be 2100lb. This is conservative. What’s the beam?
5/16 BBB is undersized for your boat, it should have a breaking strength of 8400lb
I would go with 5/16 HT.
If you change yo 1/4” you would need a new gypsy for windlass.
After the galvanizing starts to wear away, because of its larger diameter the HT can afford to loose more section area to corrosion before the chain needs to be condemned.
If you can regalvanize the chain the HT should lose no strength, the higher strength is due to alloying. G70 is heat treated so regalvanizing will affect strength.
I’d be interest to know what the price difference is.
Honestly I would consider putting 125’ of 1/4” HT on the main anchor backed with 200’ of 1/2” or 9/16” nylon line. And another 125’ of the same chain in the bilge to extend the main if traveling thru deeper anchorages in the pacific, or as a replacement if the main anchor chain is lost or needs replacement.
__________________
Num Me Vexo?
For all of your celestial navigation questions: https://navlist.net/
A house is but a boat so poorly built and so firmly run aground no one would think to try and refloat it.
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06-10-2021, 15:30
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#3
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Registered User
Join Date: Aug 2019
Location: Quebec
Boat: Cape Dory 30c
Posts: 154
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Re: Scope, All Chain Rode and Breaking Strength
Thanks good ABYC info. I do not have a windlass so gypsy can be bought for chain. I do not want rope rode. Price difference is nominal. 350 ft would provide a 10-1 scope in 35'.
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06-10-2021, 15:34
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#4
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Registered User
Join Date: Dec 2020
Posts: 750
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Re: Scope, All Chain Rode and Breaking Strength
The LENGTH of the chain is based on the depth of the water you want to anchor in.
If you are going to anchor in water that is 10 fathoms or deeper you'll wish you had > 200 feet of chain. If you never anchor in water deeper than 4 fathoms, then carrying around 350 feet of chain would be a waste... Length is a decision that has little to do with the strength...
First you decide on how LONG a chain you NEED, and then you figure the maximum weight you want to tolerate (Does 50 lbs REALLY matter???), and then you pick a grade chain that squares the circle...
Without knowing where you are sailing, and how you use your boat, any answer at all is just an uneducated guess based on what I think is best for me, not what is best for you...
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06-10-2021, 15:38
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#5
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Registered User
Join Date: Jun 2019
Location: Rochester, NY
Boat: Chris Craft 381 Catalina
Posts: 6,207
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Re: Scope, All Chain Rode and Breaking Strength
I had a similar debate for my boat. I went with 5/16 g43 because I couldn't find a big enough windlass that would pull 1/4 g70. If 200 lbs isn't a concern, I'd go with 200 feet and then add line after that. Most places where you need all chain won't need more than 200 feet.
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06-10-2021, 16:05
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#6
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Registered User
Join Date: Jan 2011
Location: Cowichan Bay, BC (Maple Bay Marina)
Posts: 9,704
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Re: Scope, All Chain Rode and Breaking Strength
This is a superb analysis. It helps explain how others made their choices, I'll betcha. But what they've done may not apply to you. If you perform the exercise as Bill details, you'll have YOUR answer. It's the only one that matters.
Quote:
Originally Posted by BillKny
The LENGTH of the chain is based on the depth of the water you want to anchor in.
If you are going to anchor in water that is 10 fathoms or deeper you'll wish you had > 200 feet of chain. If you never anchor in water deeper than 4 fathoms, then carrying around 350 feet of chain would be a waste... Length is a decision that has little to do with the strength...
First you decide on how LONG a chain you NEED, and then you figure the maximum weight you want to tolerate (Does 50 lbs REALLY matter???), and then you pick a grade chain that squares the circle...
Without knowing where you are sailing, and how you use your boat, any answer at all is just an uneducated guess based on what I think is best for me, not what is best for you...
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__________________
Stu Jackson
Catalina 34 #224 (1986) C34IA Secretary
Cowichan Bay, BC, SR/FK, M25, Rocna 10 (22#) (NZ model)
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06-10-2021, 16:18
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#7
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Moderator
Join Date: Feb 2010
Location: La Ciudad de la Misión Didacus de Alcalá en Alta California, Virreinato de Nueva España
Boat: Cal 20
Posts: 20,489
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Re: Scope, All Chain Rode and Breaking Strength
Quote:
Originally Posted by Mara Mae
Thanks good ABYC info. I do not have a windlass so gypsy can be bought for chain. I do not want rope rode. Price difference is nominal. 350 ft would provide a 10-1 scope in 35'.
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What’s the beam of the boat, that may govern over length.
Even if you use all chain you still want nylon snubbers, 1/2” then.
Do you have a chain stopper? Even if you get a windlass you want to use the chain stopper to carry the anchor loads, the windlass is for raising the chain and anchor, not for securing the boat.
__________________
Num Me Vexo?
For all of your celestial navigation questions: https://navlist.net/
A house is but a boat so poorly built and so firmly run aground no one would think to try and refloat it.
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06-10-2021, 16:37
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#8
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Registered User
Join Date: Sep 2011
Posts: 191
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Re: Scope, All Chain Rode and Breaking Strength
Quote:
Originally Posted by Mara Mae
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Quote:
Originally Posted by BillKny
(Does 50 lbs REALLY matter???).
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I would think so yes.
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06-10-2021, 17:28
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#9
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Registered User
Join Date: Aug 2019
Location: Quebec
Boat: Cape Dory 30c
Posts: 154
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Re: Scope, All Chain Rode and Breaking Strength
Thank you. Based on this feedback I am going to investigate 350' of 1/4" G70 galv. all chain rode on a Mantus M1 or M2 45 lb anchor.
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06-10-2021, 17:34
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#10
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Registered User
Join Date: Jul 2020
Location: Wrangell Alaska
Boat: Beneteau Oceanis 38.1
Posts: 446
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Re: Scope, All Chain Rode and Breaking Strength
Maybe someone can correct me if I’m wrong. But I always thought chain had a big benefit to us over its weight when anchoring out.
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06-10-2021, 17:48
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#11
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Registered User
Join Date: Oct 2019
Location: Kennebunk ME
Boat: Owner built 60’ Aluminum Expedition Yacht.
Posts: 1,854
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Re: Scope, All Chain Rode and Breaking Strength
To what structure are you going to attach a 9,000 pound load. At one point chain becomes a solid link between your boat and anchor.
I would spend more time thinking about snubber calculations, chafe and a waterline attachment point.
All the elements are important not just the chain.
It’s difficult to recommend anything without knowing what’s in the rest of your anchoring system.
Happy trails to you.
The manatee crew.
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06-10-2021, 18:24
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#12
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Writing Full-Time Since 2014
Join Date: Nov 2008
Location: Deale, MD
Boat: PDQ Altair, 32/34
Posts: 9,568
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Re: Scope, All Chain Rode and Breaking Strength
Quote:
Originally Posted by Adelie
Per ABYC anchor load chart, 60kt wind loads for a boat your length will be 2100lb...
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Incorrect. The ABYC is the recommended working load. The actual load is 3-5 times less than this. The ABYC recommended working load for 30' is 1400 pounds, and the actual load is several times less. The chart does NOT say this is the actual load and that is not what it represents. Many testers have confirmed this. A common misunderstanding.
This is the chart:
http://data:image/png;base64,iVBORw0...AAAElFTkSuQmCC
A 1/4-inch G43 hass a working load of 2600 pounds. That is all you need. In fact, 1/4-inch BBB has a WLL of 1300 pounds and arguably meets the 1400-pound requirement. But I'd go with the G43.
And you don't need 300 feet. 200 feet backed with rope is plenty. 100 feet backed with rope is enough most places (if you are in water deeper than 15 feet, the rope won't be on the bottom anyway. But you won't often anchor in over 15 feet).
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06-10-2021, 18:56
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#13
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Moderator
Join Date: Feb 2010
Location: La Ciudad de la Misión Didacus de Alcalá en Alta California, Virreinato de Nueva España
Boat: Cal 20
Posts: 20,489
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Re: Scope, All Chain Rode and Breaking Strength
Quote:
Originally Posted by thinwater
Incorrect. The ABYC is the recommended working load. The actual load is 3-5 times less than this. The ABYC recommended working load for 30' is 1400 pounds, and the actual load is several times less. The chart does NOT say this is the actual load and that is not what it represents. Many testers have confirmed this. A common misunderstanding.
A 1/4-inch G43 hass a working load of 2600 pounds. That is all you need. In fact, 1/4-inch BBB has a WLL of 1300 pounds and arguably meets the 1400-pound requirement. But I'd go with the G43.
And you don't need 300 feet. 200 feet backed with rope is plenty. 100 feet backed with rope is enough most places (if you are in water deeper than 15 feet, the rope won't be on the bottom anyway. But you won't often anchor in over 15 feet).
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The link didn't work.
I have found a bunch of different versions, some use wind strength, some use working load, storm load, violent storm. I believe that ABYC only provided the loads based on wind strength without any qualifying statement.
It looks like the 2100lb value I threw out was somebody's interpolation between 42kt & 60kt, probably 52kt. 42 or 52kt wind strength seems like a reasonable design point for a storm. Yeah, something stronger will hit you someday but the table is conservative and overestimates loads to begin with.
If I was cruising, I wouldn't use 30kt, I'd use 42 or 52kt.
For staying somewhere near home, 30kt would be a reasonable design assumption.
OP wants all chain, better that than almost no chain. Get him/her to go with a snubber and it'll be fine.
__________________
Num Me Vexo?
For all of your celestial navigation questions: https://navlist.net/
A house is but a boat so poorly built and so firmly run aground no one would think to try and refloat it.
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06-10-2021, 18:59
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#14
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Writing Full-Time Since 2014
Join Date: Nov 2008
Location: Deale, MD
Boat: PDQ Altair, 32/34
Posts: 9,568
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Re: Scope, All Chain Rode and Breaking Strength
Quote:
Originally Posted by Adelie
The link didn't work.
I have found a bunch of different versions, some use wind strength, some use working load, storm load, violent storm. I believe that ABYC only provided the loads based on wind strength without any qualifying statement.
It looks like the 2100lb value I threw out was somebody's interpolation between 42kt & 60kt, probably 52kt. 42 or 52kt wind strength seems like a reasonable design point for a storm. Yeah, something stronger will hit you someday but the table is conservative and overestimates loads to begin with.
If I was cruising, I wouldn't use 30kt, I'd use 42 or 52kt.
For staying somewhere near home, 30kt would be a reasonable design assumption.
OP wants all chain, better that than almost no chain. Get him/her to go with a snubber and it'll be fine.
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I've been having trouble with links the last few days.
Remember, ABYC NEVER states these are loads. They are recommended gear specs. Not the same thing.
Google ABYC h-40 table 1. There is only one true version of a standard. Older versions of this table stated windspeeds, but they required complex explanation (they were not actual loads), so ABYC removed them. No guessing. this is from this forum:
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