Chain & Catenary: Challenging a Maritime Myth


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Dick
Dick
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Hi all,
I write periodically on ground tackle effectiveness and contributing factors. The attached article is one of those. As always, I invite questions and comments.
Dick Stevenson, s/v Alchemy
Dick
Dick
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Hi all,
The article may be more easily seen published, recently edited and with pictures at:
https://stevedmarineconsulting.com/choosing-chain-challenging-a-maritime-myth
My best, Dick Stevenson, s/v Alchemy
Philip Heaton
Philip Heaton
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Dick
Excellent article. Reminds me of the advice I received when we changed our anchor from a 20kg Delta to a 25kg Manson Supreme: if people are not laughing because your anchor looks too big, then it is NOT big enough.
Cheers
Phil
Bill Balme
Bill Balme
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I confess I was worried when I read the article's title - having just spent a boatload of money on new chain for Toodle-oo! How gratifying to then find out that (at least in Dick's opinion - and mine) I picked right! Instead of being tempted to 3/8 chain, I went for a longer length of 5/16HT - Thank you Simon Currin for the prompt! Looks like I got it right for a change!

Our 13.5M 17T boat carries a 30kg Spade - as recommended for a 20M, 20T boat! - Bigger is better!!!
edited by bbalme on 3/10/2019

Bill Balme
s/v Toodle-oo!

Dick
Dick
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Hi Bill,
I am glad we ended up on the same page chain wise.
I consider many, maybe most, cruising boats I see as under-anchored. And most guides for anchors are not in line with what I suggest. It costs just too little money (and not that much extra weight) to do it right and sleep well, even in marginal conditions in boisterous weather. Especially nowadays with the new generation of anchors such as your Spade.
My best, Dick Stevenson, s/v Alchemy
Dick
Dick
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Hi Phil,
Thanks for the kind words. And, yes, those of us who wander widely and need to be able to anchor safely in marginal conditions often have anchors that are "laughable" in size. That said, I have so become accustomed to cruising level anchors, that it is easy for me to slip into "laughter" when I walk around marinas and boats where I clearly feel that that choice of anchor is best described as a "toy" and is best thought of as mere marine decoration rather than as a function piece of gear.
My best, Dick Stevenson, s/v Alchemy
Philip Heaton
Philip Heaton
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This thread seems to be running out of legs which is unusual for an anchoring thread, so ... while there is no argument about 8mmHT chain vs. 10mm chain (despite Brexit we are metric folks these days) when there are such strong winds that the chain is fully taught and catenary has essentially disappeared, I would posit that there are situations where heavier chain is an advantage: namely lighter winds where the catenary is in evidence and with heavier chain reduces the swinging circle. Clearly this is an advantage in crowded anchorages. I have not done the sums, but the impact of the weight difference on a cruising boat >12metres in sailing performance (given the vast amount of stuff folks carry) is likely to be marginal. Cost if course is a factor.
Simon Currin
Simon Currin
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Phil,
What you say makes sense and is why we still carry our 10mm chain having switched to 8mm a few years ago. I cannot back my observations with any science but we have noticed no difference in our boat’s swinging behaviour in moderate conditions.
Simon
Dick
Dick
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Hi Phil,
Thanks for the close read of my article. I suspect that the “running out of legs” comment wise has more to do with the numbers who read the article than the agreement as to its arguments.
You are, of course correct, that heavier chain keeps the boat closer to the anchor in light winds. At the exaggerated limits of your argument you are approaching a mooring rather than an anchoring situation. Anchoring in crowded anchorages, which sometimes also have the challenge of attracting the less experienced, is always fraught with anxiety. I suspect that the amount of wandering that a boat does differs, but not by too much, when with 3/8ths/10mm chain vs 5/15/8mm. I also seem to be fortunate in not being challenged very often by crowded anchorages.
My usual ploy, when possible, in crowded anchorages, is to anchor on the fringes of the fleet which often means anchoring deep, deeper than most who go to crowded anchorages like to do or are experienced doing: 15-20 meters is not uncommon. Being away from other vessels makes for a much more comfortable night and far fewer fire drills if the winds shifts and/or gets more potent.
This can be made easier by carrying more chain as the chain choice is lighter. My research has a 46-pound difference between 5/16 and 3/8 ht per 100 feet. For me, that translates into about 132 pounds/60kg weight differential. Putting just a bit of that weight in the anchor (esp. a Spade or other new generation anchor) will ensure far more effective anchoring in all conditions than weight placed anywhere else in your ground tackle system. And a significant decrease in weight at the bow.
In the end, I am most concerned with boisterous conditions and/or marginal anchorages and less so with crowded anchorages, where the down side is most likely a dinged topsides more than catastrophe.
My thoughts, my best, Dick Stevenson, s/v Alchemy
freedomandadventure
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hi Dick,
i agree with everything you have said here on anchor systems. i would add though that we use 8 plait nylon for our snubber instead of 3 strand for the simple reason that it doesnt twist the chain around the snubber when loaded like the 3 strand does. i have seen the twisting be very difficult to unwind to release the snubber when under load just when you want to raise the anchor. i know the 8 plait is less stretchy than 3 strand so we let out more snubber to soften the shocks. our storm snubber is 20m long and our day to day snubber is 7m long [it was 10m but got chaffed].
cheers
andrew
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