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-   -   Chain anchor rode length (http://www.sailnet.com/forums/gear-maintenance/59039-chain-anchor-rode-length.html)

braidmike 10-18-2009 08:09 PM

Chain anchor rode length
 
We are within a year of begining our circumnavgation. Most of the systems on our old Ericson 35 have been rebuilt/replaced, the latest being the addition of a Maxwell windlass. The next step is the purchase of 5/16 hi-test anchor chain. The question: HOW MUCH?? Our anchoring ground will vary from leaving Southern California, to the standard stops on an around the world trip of ten years (the wildest current guess). From what I've been able to read and gather, anchoring in up to 80' may be inevitable. A half keg of chain is 270' (what I have now, just some oddball size that doesn't seem to match anything else manufactured in the world). Along with 250' of octabraid on the main, I'm hoping that will be sufficient. The old chain will be used for the stern anchor (at least the 200' that is still not too corroded). Any advice from those that have been?

Paul_L 10-18-2009 08:30 PM

That is something close to 600lbs of chain. And mostly carried in the ends. Are you sure you want to load down your Ericsson with this much weight?

Paul L

braidmike 10-18-2009 08:48 PM

The weight is one of those 'trade-offs'. Compared to getting a good nights sleep, it's one of those comprimises that take a bit of thought. The boat sails well with the (until now) 300#s in the forward locker.

Paul_L 10-18-2009 09:03 PM

On boat like yours I can see having 150-250 of chain on the bow anchor, with another 50 available for the secondary. But every one has to make their own trade-offs as too weight. In reality you will mostly have 150 ft or less chain out the vast majority of time. You will sail with all the weight, all the time.

Paul L

Waltthesalt 10-18-2009 09:27 PM

Check our Earl Hinz's book The Complete Book of Anchoring and Mooring. It's the most complete book on the subject that I know of and will answer your questions. The only area where I had to find other info was my anchoring cleats (I don't use a windlass). I found that I needed to look at the bolts holding it down and thier shear streingth compared to the load. It turns out that SS bolts are a lot weaker in shear than you might think. I ended up putting in more/larger bolts with a big backing plate.

klem 10-18-2009 09:29 PM

You will likely have to ride out some weather at anchor at some point and there really is no substitute for all chain at that point with a good snubber. When it gets really bad, the chafe resistance of the chain becomes crucial because even a good snubber can fail. I would think that you would want the ability to anchor on all chain with good scope in all reasonable depths(up to 50'). So a half keg with some additional heavy rope rode would be my choice, the additional rode for when it is super deep.

As far as putting 200' of chain on your stern anchor, that will make it very hard to use. It sounds like the chain won't fit your windlass and that would me re-leading it forwards anyways. Much more than 50' or so and it will become unmanageable. If you have the choice, storing this closer to the centerline of the boat would good. Up to a reasonable point, weight on a boat isn't too bad but the issue is having it in the ends because your inertia will increase which will put the boat out of phase with the waves. In extreme cases, poorly loaded boats pitch wildly. Since you have already been carrying the weight of the primary anchor and chain forwards and haven't had problems, I wouldn't worry about it but it is a considering when packing.

tdw 10-18-2009 09:36 PM

I'm butting in here , not being one of those who has done it all, but.....

The occasions when you will anchor in 80+' are going to be rare.

Most times I would have thought 150' of chain would be ample with the rope for when you need to get all the chain on the bottom. Even 150' is not light weight living up front. What's the Ericsons anchor locker layout ?

If you then find the occasion to need an extra 100' of chain why not keep that separate from the other, stowed way down low and only brought out when needed. Yes it's a bore when you have to do it but keeping the weight down in the ends, is important.

I've never heard of anyone using chain (other than the first few metres) for a stern anchor. Maybe I'm wrong but I cannot see the need for it.

We currently carry 120' of chain and have found that sufficient for all our needs but have never anchored in deeper that 60'. Then I put all 120' on the bottom plus rope. We are 34' steel. displacement 5.4t (12,000 lbs).

speciald 10-18-2009 09:48 PM

I carry 100 meters on the primary but have never used more than half. reversed the chain last year and have 50 meters of new chain to use now.

Craig Smith 10-18-2009 11:17 PM

Quote:

Originally Posted by braidmike (Post 533376)
We are within a year of begining our circumnavgation. Most of the systems on our old Ericson 35 have been rebuilt/replaced, the latest being the addition of a Maxwell windlass. The next step is the purchase of 5/16 hi-test anchor chain. The question: HOW MUCH?? Our anchoring ground will vary from leaving Southern California, to the standard stops on an around the world trip of ten years (the wildest current guess). From what I've been able to read and gather, anchoring in up to 80' may be inevitable. A half keg of chain is 270' (what I have now, just some oddball size that doesn't seem to match anything else manufactured in the world). Along with 250' of octabraid on the main, I'm hoping that will be sufficient. The old chain will be used for the stern anchor (at least the 200' that is still not too corroded). Any advice from those that have been?

I'm not entirely sure how to interpret "the standard stops on an around the world trip of ten years", as ten years is more than enough time to make some considerable detours from the 'usual milk run'. That said, deep water is probably unavoidable as a lot of it is in your way across the Pacific.

Chain length required depends almost entirely on this, so discount any thoughts of catenary, helping the anchor, and other misconceptions.

On Kiwi Roa, the two main anchor rodes are 100 and 50 meters chain respectively, plus 50 and 100 meters respectively of 8-plait polyester. "From those that have been", this is more than adequate.

The main reason I am responding is to suggest you reconsider your choice of 5/16" hi-test. We would go with 1/4" high tensile G70, which saves about 35 lb per 100' of length and is still stronger. (Well actually out of the US and given an international cruising area we would be going with metric sizing but that's beside the point). There is no need to carry the extra weight of medium-lower tensile grades.

braidmike 10-18-2009 11:52 PM

Many thanks for the great feedback. I'm really appreciating the comments on the stern anchor chain length, as that will not be in use very often (when you have it sitting at the dockbox, it's hard to let it go...). The primary is easy to justify. The reason for the 5/16" is the windlass just installed is set up for it. I like the idea of keeping the weight more midships... will work for the stern anchor and associated rode. I'll ck out the Complete Book of Anchoring. Thanks for the tip. Our "milk run" plan includes plenty of time for messing about and hopefully never having to get in a hurry to be at any place at any time other than weather and current considerations. I've been told if you can anchor in Southern California you can anchor anywhere, but being old and grey and a bit cautious...
Craig, your Rocna anchor is next on the list when the rode is bought, so I do appreciate your real world experience. Given a choice between a SS plow and a SS danforth copy (because I inherited both with the boat), which would you take as a stern/backup anchor?


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