Anchor chains

I have now found the article that I refered to earlier. The writer is Evans Starzinger. The article I referd to was published in the Jan 2005 YM, a very interesting article on anchoring it is too.

Do you think if I scan it and post it IPC might get upset with me?
 
Was it something I said?

But if "Hylas" had been following this forum over past years, he would have known that I have been campaigning about inadequate chain joining shackles for a very long time.

I am no fan of tandem anchors and I find a Fisherman an excellent anchor for the dinghy; it stows flat under the thwart and you can stamp it in to the beach.
 
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The "traditionalists" who are still using Firsherman anchors, heavy chains and Tandem set anchors.. and by experience I know that NOTHING will convince them to change..

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Ah, come on. Be tolerant /forums/images/graemlins/laugh.gif There's no need for them to change.

If their method works for them, that's fine. It's just that their techniques may not apply to those who anchor in different boats, in different conditions, with different needs (light and easy anchor handling maybe).
 
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Try putting different chain sizes and lengths, and nylon rode lengths into Alain Fraisse's excellent spreadsheet available here

[/ QUOTE ]Fraysee's work is good but his models are very incomplete and do not adequately consider many scenarios. The major result is a bias away from chain, especially for larger boats, but his conclusions in general are still good advice.
 
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I'm a believer.

45lbs CQR on 90 metres of 12mm chain - though I very seldom use all of that!

It seems to me that the chain does several things:

- it provides a catenary. I don't understand Hylas' point about strong winds, but see below...

[/ QUOTE ]In extreme conditions you lose the catenary, as even heavy chain will be pulled bar-tight. Remember the Yachting Monthly testing - 15Kg anchors with over two tonnes of force on them. Do you think the 8mm chain had any catenary left in it?

Hylas' point is that, once the rode is tight, it makes no difference to holding whether the rode is chain or rope, and rope will give better shock absorption at that point. It follows that increased scope is the only way to reduce the angle of pull on the anchor.

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- it acts as a damper and cuts out snatch loads on the anchor. This might be what Hylas means if he has in mind shallow water - many people make the mistake of paying out half a mile of chain forgetting that most of it will be lying on the bottom and will come taut suddenly and offer no damping effect

[/ QUOTE ]It doesn't act as a damper once it is taut.

HOWEVER in deep(er) water this whole argument is lessened, another factor Fraysee's work doesn't adequately consider.

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- it cuts down sheering - won't stop it, but she will sheer slower dragging a pile of chain around with her.

[/ QUOTE ]Yes.
 
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Interesting point from the world of big boats - above around 20mm chain it is common to go for stud link chain instead of the common short link in order to get more weight while using the same size windlass.

[/ QUOTE ]Do not make the mistake of assuming that you can scale things.

The best way to anchor a toy boat is with a large anchor and a length of stretchy stuff. The best way to anchor a large ship is with a (relatively) small anchor and heavy chain.

Your boat (yes you /forums/images/graemlins/wink.gif) is probably somewhere inbetween.
 
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In extreme conditions you lose the catenary, as even heavy chain will be pulled bar-tight. Remember the Yachting Monthly testing - 15Kg anchors with over two tonnes of force on them. Do you think the 8mm chain had any catenary left in it?

Hylas' point is that, once the rode is tight, it makes no difference to holding whether the rode is chain or rope, and rope will give better shock absorption at that point. It follows that increased scope is the only way to reduce the angle of pull on the anchor.

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And at that load do you think that a rope will have any better shock absorption .. ?
If you're experiencing that sort of load with 8 or 10mm chain then perhaps you shouldn't be out there at anchor ?!
 
Re: You say tomato

Alain FRAYSSE is a good friend, sailing his catamaran somewhere in the remote islands of Pacific, and one of the co-author of the book :

THE COMPLETE ANCHORING HANDBOOK

You see.. there are plenty of sujects where Craig and myself agree.. like the efficiency of concave surfaces for anchors /forums/images/graemlins/grin.gif

and only a few minor points where we disagree. like the efficiency of roll bars.. /forums/images/graemlins/tongue.gif
 
There is an old thread on the old SSCA discussion board which covered the Fraysse work. I link to it here because it also featured some fairly constructive contributions from Evans Starzinger, who was referred to above by Galadriel.

http://www.ssca.org/sscabb//indexold.php?action=vthread&forum=6&topic=1733&page=0

There is much more chaff than wheat in this, partly as a result of the old permissions to allow anonymous posting. However, the "wheat" is there. Nb.: don't bother replying to the thread, even if it lets you; the forum has been replaced by a new one.

EStarzinger = Evans Starzinger
Alain POIRAUD = Hylas
 
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And at that load do you think that a rope will have any better shock absorption .. ?

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My thoughts exactly. Both Craig and Alain seem to be implying that rope is infinitely elastic.
 
So, chain is elastic?

Anchors break out, and rodes snap, and deck gear breaks, only when peak loads are reached due to the dynamic behaviour of the boat - due to yawing or waves.

Nylon will give you from 10% to 20% stretch before deforming permanently, depending on the weave. The strength will depend on the diameter. The amount of stretch will depend on the length, the square of the diameter and the force applied.

Chain has very variable strength, depending on joins and quality of manufacture, but it would be reasonable to say that 8mm chain should match 20mm nylon. Many would dispute this, offering larger or smaller rope diameters. Fine.

Looking at anchoring in 7m, with 45m rode:

Chain will give you about 2m of movement to take up a catenary, and the force involved will initially be trivial, with most of the force coming in over the last half metre up to (let us say) 3,000kg.

All nylon will give you 4.5m to 9m stretch if you choose the appropriate diameter (sorry, haven't got my tables with me), and the force will increase linearly over the whole of that distance.

That's a much softer ride than with chain, and the result is that you are much less likely to reach peak stresses when using all rope, against using all chain.

So much so, that it's best to take a bit of both worlds. 25m of chain to lie on the bottom - and 20m of nylon to do the stretching. It's just a longer snubber than most people use.

What ever anchor you use, this is the best way to minimise the forces being applied to the anchor in vessels of less than around 20m in shallow waters (<10m) when the winds get up and the waves start rolling.
 
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So, chain is elastic?

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Well, I didn't say it was but since you ask - when you take into account the effect of the catenary, it behaves as if it were elastic.

I'm not disputing the stretch qualities of nylon - merely questioning the apparent assumption that it will carry on "giving" in extreme conditions.
 
From the referenced thread on SSCA....

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We deal with the 'JAX' types in a lot of threads and still make progress, so I suspect much of the problem is Alain & Craig's absolutely constant presence. On the one hand they do have some useful knowledge, on the other hand they also bring a lot of 'marketing fluff' (perhaps a polite word for disinformation) and 'an intent to sell' which is contrary to the ethics of the boards.

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Ah, 'marketing fluff'..... What a descriptive term. Is that related to 'bum fluff'?

Nevertheless, there are some 'nuggets' emerging - which was the whole point. It's just a pity there's a lot of overburden to shift, first. Such as using lengths of firehose ( with attachment cords fitted ) slipped over one's rode, as anti-chafe. This tough stuff is 'lifed' and is readily, freely, available. So also are truck engine water hoses, from a breaker's yard. ( Not Volvo! /forums/images/graemlins/grin.gif )

I'm interested in providing more 'anti-snubbing' elasticity in the heavy-weather setup than is provided by nylon bridles alone. So here's a question for the team....

Given using chain, and stretchy nylon bridle(s) from bitts onto the chain, to take the snubbing loads as she surges/scends, how about having a small car tyre fitted onto the middle of the snubbing line, wound spirally around the circumference of this tyre a half-dozen times? This would, it seems, act much as the RubberSnubber device one sees on marina lines - only much stronger and cheaper.

Thoughts?



/forums/images/graemlins/wink.gif
 
If I understand your proposal, it'll be a source of chafe where it rubs on first and last contact with the tyre. And I'm struggling to imagine how it's all held in position - or attached in the first place.

OK, it could add stretch. How much? 30cm? Or whatever. If 30cm, that's equivalent to using 1.5 (or 3m to be conservative) more snubber length.

I think I'd prefer to simplicate and add lightness. Splash.
 
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