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Old 08-03-2010, 02:17   #1
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Anchor Chain - How Much?

Benny 41 has 190' (57m) of 3/8th chain.
It is looking pretty long-in-the-tooth.
The boat is 17,000lb (8 tonne).
I generally put out a lot of chain - and if I'm going to replace this chain I may as well get as much as I'm comfortable with.
I notice that the 190' of 3/8th is about 135kg.
I'm tempted to replace this with 250' (77m) - which will allow me 5:1 in 15m of water.
This would weigh about 177kg.
Is this too much ?
By the look of the trim and lie of the boat - I don't think an extra 40kg is an issue.
Opinions and suggestions most welcome.
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Old 08-03-2010, 06:11   #2
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Where do you anchor and what are the greatest depths? Many people who sail around the world end up anchoring in 80+ feet and need a long rode while people who stick to the bahamas rarely anchor in more than 10'. I would suggest making sure that you have 5:1 for the deepest anchorage you expect to see.

Another thing that you can do to save a lot of weight and cost if you expect to anchor in really deep water occassionally is to keep the same amount of chain that you currently have and splice on 150' or so of 3/4" line. You may not want to hang on this in a storm due to chafe but it should be just fine under normal circumstances.
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Old 08-03-2010, 07:46   #3
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I find 250' the minimum for a world cruiser for all-chain rode. If you are like me, you will often use 120' or less and that makes this length great for turning it end-to-end halfway it's usable service life. I got 300' last time I ordered.

cheers,
Nick.
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Old 08-03-2010, 08:09   #4
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Because our goat is it leave and not know where we are headed, we've set up two lengths of 400 ft each.. and we use 3/8 BBB .. a smaller size with higher strength..
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Old 08-03-2010, 08:23   #5
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I have found 250' to be sufficient, but would be able to back that up quickly with nylon if I ever come into a situation where I'd need to anchor in more than 50 feet.

Like Nick, I have found it useful to switch the rode end-for-end to extend its useful life. Unlike Nick, I have no idea when a chain needs to be retired. I'd love to know, I think, except that Nick has been causing me to spend too much money lately.
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Old 08-03-2010, 08:58   #6
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currently cruising in mexico and we have 300' 3/8 bbb and 150' 3/4" rode for back up. roughly every where we anchor is no more than 30' . Most cruisers we've met have roughly the same in chain. limmer.
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Old 08-03-2010, 14:28   #7
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G'Day Fraidy,

First, we've had about 280' of 10 mm on each of our Insatiables, and have found this to be adequate for our purposes. We live on the hook throughout the S Pacific, and have never had to anchor in more than 85', and rarely over 60'. On I-one we had a long bit of nylon spliced to the bitter end of the chain "just in case", but never actually used it. In our experience, the oft-quoted 5:1 or 7:1 scope requirement is not particularly valid at larger depths. I won't get drawn into yet another theoretical battle about calculated anchor loads, but rely on our hard won experiences which say that somewhere around 3:1 in greater depths has worked. When faced with impending cyclones, we have sought out anchorages where more reasonable depths were available!

As to ageing chain -- what do you mean "long in the tooth"? If you mean surface rusting, then re-galvanizing is a much cheaper alternative to replacement. If the chain is significantly worn (in the area where the links bear upon each other), then replacement is in order. Also if the chain has ever been stressed to the point of slight elongation I'd replace it.

And the chap who is carrying two 400' lengths of 3/8" chain in his once lightweight Benny... that's REALLY a lot of weight to carry about, and may represent a bit of overkill!

Cheers,

Jim and Ann s/v Insatiable II lying Towlers Bay, NSW, Oz
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Old 08-03-2010, 15:49   #8
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Originally Posted by Jim Cate View Post
G'Day

And the chap who is carrying two 400' lengths of 3/8" chain in his once lightweight Benny... that's REALLY a lot of weight to carry about, and may represent a bit of overkill!

Cheers,

Jim and Ann s/v Insatiable II lying Towlers Bay, NSW, Oz
Even thou shes a benny, shes pretty heavy at 24k across the scale empty.. The book says 18.5 but I've got the weight tickets.. and one length is run down thru a pipe to just forward of the keel so most of the weight is off the bow.. Even with the added weight, she's well balanced.
I just dont ever want to be caught with less than I need......
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Old 10-03-2010, 05:06   #9
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Originally Posted by Randyonr3 View Post
Even thou shes a benny, shes pretty heavy at 24k across the scale empty.. The book says 18.5 but I've got the weight tickets.. and one length is run down thru a pipe to just forward of the keel so most of the weight is off the bow.. Even with the added weight, she's well balanced.
I just dont ever want to be caught with less than I need......
So it's 6k over designed weight to-start? (A serious quality issue). You could make a big improvement if you lighten the load. She may be well balanced, but her performance could improve significantly. There are good arguments for mixed-rode providing better holding than all-chain.

References:
http://www.petersmith.net.nz/boat-anchors/catenary.php
Catenary & Scope In Anchor Rode -- Anchor systems for small boats” by Peter Smith)
http://alain.fraysse.free.fr/sail/rode/rode.htm
“Tuning an anchor rode” by Alain Fraysse
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Old 10-03-2010, 06:31   #10
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I just went through this decision making process after arriving in the Carib. In my trip from Australia through Indonesia, across the Indian Ocean, around Africa and across the South Atlantic to Brazil and on to the Caribean, I had 100 meters of cheap chinese 3/8 chain as my main bit of gear with a muir horizontal windlass. All went well until the chain started skipping here in the Carib. The problem was general wear and tear of the chain, which may also have become a bit elongated as well, and a chainwheel that was also feeling its age of 15 years of heavy use as I was on the hook almost exclusively for the past five years.

I am getting a new chain wheel, and I decided to go with two sets of 200 feet of 3/8 HT chaiin with a 150 foot 9/16 rode spliced to the chain as replacement for the 100 meters. This will be a new arrangement for me, and there is the possibility that the rode will not be grabbed from the chain wheel very well, but after talking to the muir folks, I think I will be ok as there will always be the weight of the chain providing tension on the rode when the I am retrieving the anchor .

My thinking was that the two or three times there was no choice but to to anchor in water deeper than 60 feet or so, I would have been better off having chain and rope than all chain. I prefer to anchor betweeen 20- 30 feet most of the time, so normally I will be riding to all chain. (I also use a longer snubber than most folks, about 40 feet of three strand nylon). By having two full sets of gear , if one should decide to take a permanent leave of abscence, I will still have a a proper replacement!

If the chain starts wearing, I will cut off the splice and end for end the chain and the roode and resplice. The weight will be about the same as I used to carry 30 meters of chain in the locker as a spare, and the bulk should be about the same as well. I am also installing a chain stopper to keep surge loading off the windlass when retrieving the chain. When I have the funds, I will probably replace my aging clone 20 K CQR with a Ranchor 20 K.

Juno is a monhull, a Radford 40, steel hull and aluminum deck, and I am guessing she weighs 16 tons with normal provisioning. Maybe this haul out I will be on a lift that has a weighing device that actually works!

Most cruisers in the 36- 45 foot range that I met had 100 meters as their primary rode, except for the small boats less than 35 feet They all said they just did not want to be hassled with handling nylon rode, and they felt the extra weight on the bottom was a plus. But as W. Van Dorn discusses in excruciating techniacal detail in the book Oceanography and Seamanship, this is not such a great idea since chain does not not stretch and the weight really does not serve to add significantly to holding power in most situations.

Hope this helps!

Tom
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