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14-11-2016, 10:20
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#16
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Registered User
Join Date: Sep 2013
Location: Alert Bay, Vancouver Island
Boat: 35ft classic ketch/yawl.
Posts: 1,980
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Re: Anchor chain size advantages
45ft of 3/8 chain weighs about 600lbs, that is why you never dragged despite being in an area with strong tides and winds. The Caribbean is a pussycat by comparison. 5/8 is about 1/2 the weight. The anchor only makes a difference if you are unable to set an adequate wt and length of road. People who habitually use crowded anchorages worry about anchors, people who don't just lay out a hundred feet or two of heavy chain.
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14-11-2016, 10:27
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#17
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Registered User
Join Date: Aug 2006
Location: Skagit City, WA
Posts: 25,480
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Re: Anchor chain size advantages
Quote:
Originally Posted by roland stockham
45ft of 3/8 chain weighs about 600lbs, that is why you never dragged despite being in an area with strong tides and winds. The Caribbean is a pussycat by comparison. 5/8 is about 1/2 the weight. The anchor only makes a difference if you are unable to set an adequate wt and length of road. People who habitually use crowded anchorages worry about anchors, people who don't just lay out a hundred feet or two of heavy chain.
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Wrong. 45 ft weighs about 67 lbs. Think about it, ever pull up an anchor by hand in 50 ft of water? At 600# you must be Arnold Scwartzenegger!
__________________
"I spent most of my money on Booze, Broads and Boats. The rest I wasted" - Elmore Leonard
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14-11-2016, 10:42
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#18
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Moderator Emeritus
Join Date: Oct 2013
Location: Jacksonville/ out cruising
Boat: Island Packet 38
Posts: 31,351
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Re: Anchor chain size advantages
For those that want heavy chains to dampen the jerk effect, try either a kellet or a snubber, or both. Snubber is the way I go, but a kellet woudl be more effective than heavy chain
From my little experience anchoring in the shallow waters that I do at 35 to 40 kts of wind, 3/8" is bar tight, and I'm not concerned until higher than 40 kt winds.
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14-11-2016, 10:45
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#19
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Moderator Emeritus
Join Date: Oct 2013
Location: Jacksonville/ out cruising
Boat: Island Packet 38
Posts: 31,351
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Re: Anchor chain size advantages
I think 3/8" is 65% heavier than 5/16"
5/16" is .93 lbs per ft and 3/8" is I think 1.41 lbs per ft.
I suck at math so you do the numbers
300' of 5/16" is 279 lbs
300' of 3/8" is 423 lbs.
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14-11-2016, 10:49
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#20
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Registered User
Join Date: Jun 2010
Location: Easton, MD
Boat: 15' Catboat, Bristol 35.5
Posts: 3,510
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Re: Anchor chain size advantages
Put the weight in the anchor. Use a little chain and mostly rode.
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14-11-2016, 11:33
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#21
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Registered User
Join Date: Aug 2006
Location: Skagit City, WA
Posts: 25,480
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Re: Anchor chain size advantages
Interestingly, anchored at the Tobago Cays in about 13 ft and pure white sand bottom, there was a steady 33-35 wind, with occassional gusts to maybe 38+. I snorkeled the anchor. I was in my 42 ft catamaran with 5/16HT chain and a Delta anchor. This was an interesting example as there was zero wind chop on the water as I was only maybe 100 ft from the beach (beach on the windward side.) At those winds speeds there was still pretty good catenary in the chain. The anchor was buried so deep you couldn't see it, as was probably 12-15 ft of chain still in the sand before it started rising up. I think wind speed would rarely be an issue on chain, but snubbing up from water action for sure.
__________________
"I spent most of my money on Booze, Broads and Boats. The rest I wasted" - Elmore Leonard
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14-11-2016, 11:41
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#22
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Moderator Emeritus
Join Date: Oct 2013
Location: Jacksonville/ out cruising
Boat: Island Packet 38
Posts: 31,351
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Re: Anchor chain size advantages
There is a formula for wind speed to force, I have seen it, of course it makes a lot of guesstimates on how much wind drag the average boat has, but just pure wind, its not much.
Then you also see how much more load you get with increasing wind and how completely non linear it is.
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14-11-2016, 11:45
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#23
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Registered User
Join Date: Jun 2010
Location: Easton, MD
Boat: 15' Catboat, Bristol 35.5
Posts: 3,510
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Re: Anchor chain size advantages
That's true. The force of the wind is a function of the wind speed squared.
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14-11-2016, 14:50
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#24
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Marine Service Provider
Join Date: Sep 2014
Posts: 178
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Re: Anchor chain size advantages
For those claiming chain weight isn't so important. Why then do you put out more chain in stronger winds?
Sent from my iPad using Cruisers Sailing Forum
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14-11-2016, 15:01
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#25
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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: Anchor chain size advantages
Quote:
Originally Posted by Herreshoff
For those claiming chain weight isn't so important. Why then do you put out more chain in stronger winds?
Sent from my iPad using Cruisers Sailing Forum
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The funny thing about this thread is that there is room for everyone to be partially right.
- Scope helps. Lower angle, more catenary (chain), more stretch (rope).
- Catenary helps. Not much in shallow water (<10'), but quite a bit in deep (>20 feet) water.
- A kellet can help, particularly by keeping rope away from the keel. The effect is about the same as the same mass of chain, obviously.
- More weight in the anchor helps. Hold is typically about mass^1.1, but the exponent is greater in some bottoms.
What is the correct safety factor, when folks speak of "sleeping at night" rather than anything calculated? How long is a piece of string?
It's rather silly to think that this could be one-size-fits-all. My answer (which I will not share) works for my boat, where I am.
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14-11-2016, 15:09
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#26
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Registered User
Join Date: Aug 2006
Location: Skagit City, WA
Posts: 25,480
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Re: Anchor chain size advantages
Quote:
Originally Posted by Herreshoff
For those claiming chain weight isn't so important. Why then do you put out more chain in stronger winds?
Sent from my iPad using Cruisers Sailing Forum
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There's an anchoring concept called "scope". Look it up.
__________________
"I spent most of my money on Booze, Broads and Boats. The rest I wasted" - Elmore Leonard
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14-11-2016, 15:14
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#27
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Registered User
Join Date: Jun 2010
Location: Easton, MD
Boat: 15' Catboat, Bristol 35.5
Posts: 3,510
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Re: Anchor chain size advantages
Quote:
Originally Posted by Herreshoff
For those claiming chain weight isn't so important. Why then do you put out more chain in stronger winds?
Sent from my iPad using Cruisers Sailing Forum
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SCOPE!!!!!!!!!!!!!!!!!!!!1
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14-11-2016, 15:54
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#28
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Marine Service Provider
Join Date: Sep 2014
Posts: 178
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Re: Anchor chain size advantages
I know what scope is. Thanks for that.
What I was getting at is that it isn't just the angle that is important. The right angle helps the anchor dig and stay holding but It's the weight of the chain trying to pull tight between the anchor and the bow that keeps the pressure off the anchor most of the time. In winds under 20knots you would put very little load on the anchor itself. The heavier the chain, the greater this effect is.
In my opinion at least.
Sent from my iPad using Cruisers Sailing Forum
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14-11-2016, 16:49
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#29
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Registered User
Join Date: Sep 2011
Location: On a boat
Boat: 1987 Cabo Rico 38 #117 (sold) & 2008 Manta 42 #124
Posts: 4,172
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Re: Anchor chain size advantages
We went with 3/8" G4 but could have come down to 5/16" G7 and gone with a bigger heavier anchor than our 55# spade. Most of our anchoring puts out less than 100 feet of chain... which weighs 1.49 pounds for our G4. 100 Feet of G7 would weigh 1 pound a foot. So, I'd could have saved 49 pounds - which could have gone into the anchor instead.
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14-11-2016, 18:08
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#30
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Registered User
Join Date: Sep 2015
Posts: 184
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Re: Anchor chain size advantages
FWIW this is my take on it.
I am in favour of using the greatest total weight in anchor and chain that is manageable.
In my opinion the variable you can play with is the weight/length of chain. There is no doubt that heavier chain for a given length will give better catanary and better holding. Heavier chain may create problems with your windlass when weighing anchor in deeper water. The obvious solution IMHO is to carry the smaller diameter chain, but a greater length of it.
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