Which anchor chain is preferable

[LadyInBed]

Given the figures below (which I think are about right) and that you reckon your boat will carry say 200 lbs of chain in bow.
Which is the better option, shorter length of heavier chain or longer length of lighter chain?

3/8" 10mm (23.466 ozs/ft) 132 lbs/90ft so 200 lbs = 136 feet
1/2" 13mm (37.333 ozs/ft) 210 lbs/90ft so 200 lbs = 85 feet
5/8" 16mm (57.422 ozs/ft) 323 lbs/90ft so 200 lbs = 55 feet

Does anyone carry a 56 lbs 'lump weight' as a supliment?

 

[hylas]

Re: The RIGHT choice..

Should I give my own opinion about chain??.. I perfectly know that some people will disagree.. but..

The main and ONLY advantage of the chain is that it is the only and perfect mean to avoid shaffing of the anchoring rode on agressive sea beds...

Except this point, chain has all disadvantages..:
Stored in the bow chain locker, it ad an heavy weight where it should not be
- Chain is working on the opposite it should work:
o with light wind, it give a perfect horizontal pull to the anchor and the best holding
o with moderate wind, its weight and catenary effect give a perfect shock absorbing effect.
o As the wind build up, the chain will become more straight (and this with as few as 25/30 knots of wind) then the pulling angle will increase and as a consequence, the holding of the anchor will decrease.
o When the shock absorbing effect will be necessary, the "bar tight" chain will not give it any more..

If there will be some waves entering the mooring place, the resulting shocks will be then directly transfered to the anchor, which then has more chance to break free.. and more serious, the chain is subject to high "picks" of pulling force and has very high risks of breaking..

Which lenght of chain??

During the last seven and half months, I spent 129 days moored (out of 228) into 61 different moorings. The mean water height has been 6.50 metres and the scope 5/1. The total lenght of the mooring line was about 30 meters for which 23.5 metres has been lying on the bottom (30 - 6.50 m)
Therefor, I believe a lenght of about 25 meters will be perfect.. If the water height is less, then you will be anchoring with an all chain line.. if the wind build up.. you will give more lenght but the wind will push the boat and the rope line will not shafe on the bottom..

Which length of anchoring rode??

Holding is in direct relation with the pulling lenght of the rode.. (or better, the pulling angle).
Generaly speaking, with a scope of 4/1 you will have about 55 % of the maximum holding of the anchor, with a scope of 6/1 about 70 % with a scope of 8/1: 80 % and with 10/1 about 85 % the maximum. - 100 % holding will be achieved with an horizontal rode or a "Infinite/ 1" scope.
Increasing the scope will be efficient up to 10/1 - With more than 10/1, a large increase of the scope will only give a negligeable increase of the holding... Therefor, the total lenght of the mooring line has to be adapted in relation with the conditions you are expecting to meet and should be about ten times the water height you will have to anchor in.. (I suggest 100 meters)

What to use with the chain??

Natural fibers are no longer used.. out of "Chemical" fibers, the one which has the best elasticity (shock absorbing effect) is polyamide (Nylon, Perlon, Enkalon...).. as the breaking strenght of the 10 mm chain is 5 tons, a 16 mm polyamide line will be well adapted.. (5.6 tons) Don't oversize the rope.. Yes you will increase the strenght but at the same time you will decrease the elasticity.. and "Elasticity" is the secret..

You have the choice of three strands rope or eight strands rope (also called "square line") Eight strands rope is better..

How to connect rope to Chain??

Remember: A CHAIN HAS THE RESISTANCE OF ITS WEAKEST LINK...

a) With an "eye" splice over a thimble and then a shackle on the chain..
ALWAYS use a shackle one size biger than the chain.. and secure the pin with a monel wire.
This is a perfectly safe solution but the eye splice will have difficulties to go throuh the bow roller.. will no pass the windlass gipsy and will never go through the deck pipe...

b) with a rope to chain splice..
Two ways: the wrong one and the right one..
a) NEVER splice the rope over the rope after a "U" turn into the last chain link.. you will loose about half of the rope resistance
b) Make a direct rope to chain splice. This is quite easy to do.. when you know how!!!.. Unfortunately it is not possible to make drawings on this forum, but leave me your E.mail address and I will send you free and personnally, all necessary explanations..

I can spend hours or even days talking about this subject.. giving you looonnnggg mathematical formulas, and if necessary to convince poeple, I will.. This is a complex and highly technical subject and I'm not planning to write pages about it on this forum....

Last point, I'm currently in the LAS PALMAS (Canaria) harbor covering the A.R.C. event.. I had the curiosity to check the mooring line of those boats which will cross the ocean and spend plenty of time anchored in the Caribean.. I was affraid to realise than more than half the float has a dangerous mooring line.. (Not talking about inadequate anchors) Main points are:
A too small, rusted and not secured shackle
The use of "beautifull stainless steel anchor connector" The most common one has an axe drilled to put a "security " screw on the opposite side.. although this is a wonderfull idea to avoid unscrewing of the axe.. the hole in the middle of the axe decrease the strenght. - For a 5 tons chain resistance, this connector has only three tons of resistance.. check yours!!!.
Swivels.. theory is perfect, but under loads, swivels doesn't work.. but more than that, it is important to check their breaking strenght.. ?Not only with a "on line" pull but also with a side way pull..
Connecting links.. they have a breaking strenght of only few hundreds of kilo.. NEVER use them on a mooring line.

What to use to connect the anchor and and the chain??

a shackle is perfect.. as before, always one size bigger than the chain..and secure the pin..
the simplest and perfect way is to use a toggle.. the same you use for your rigging.. and again one size bigger than the chain (12 mm for 10 mm chain)

Well.. anymore question?? :0)

Fair winds and peacefull anchorages..

 

[neil_s]

I don't think there's much advantage in overweight chain, after all you have to heave it all up again, sometime. As far as length goes, I tend to agree with Hylas - I have 20m of 'average' weight chain and then warp. I must say though, that when all the chain has gone over the bow roller and you are on to the rope, the boat tends to shear about more and you need to make sure that the parcelling at the stem head is good. All chain does give you a warm comfy feeling - perhaps I'll buy a bit more.....

 

[LadyInBed]

Re: The RIGHT choice..

Wow! So you reckon my 200 lbs should be 85 feet (26 mtrs) of 1/2" 13mm chain.
What about a lump weight (anchor chum?) on the rode, does it provide any benefit or is it just a liability?

 

[hylas]

Re: The RIGHT choice..

a Lump weigth.. what is also called an "Angel".. GADGET..
The weight of your anchor chum will be around 10 kg.. this is the weight of 4 meters of 10 mm chain..
Ad 4 meters more.. very easy, cheap and it works...

 

[LadyInBed]

Re: The RIGHT choice..

So 56 lbs is twice as much as is required. The reason I asked about it was for load spreading, rather than adding more chain/weight on the bow.

 

[ccscott49]

I have 160' of 5/8" chain, which I feel is a bit overkill even for my great beast, if I replace my anchor winch, one day, I will go for much longer 1/2" chain. The reason for this is I need plenty of chain and the boat is ballasted astern for the anchor chain weight she has now. Aren't big anchor winches bluidy expensive!! Apart from one from Australia for some reason.

 

[wpsalm]

Re: very interesting but....

agree with what your saying but why is square braid preferable to 3 strand ? I prefere braided line because, it lays nice and comfy in the anchor rode locker but its shock absorbing ability is no where near that 0f 3 strand....

 

[hylas]

Re: very interesting but....

up to my opinion square line is better (but also more expensive) for two reasons:
1 - it is easier to splice on the chain with 2 x 4 strands
2 - and also when stored in the "chain" locker it doesn't make "coques" (this is a French word, but as I'm in a Cyber cafe I don't have my big dictionary with me.. I apologize..) "coques" means strands making small loops..
Otherwise, the quality of both are very similar...

 

[Anchorite]

Re: very interesting but....

Le mot est "kinks". A ne pas confondre avec une utilisation "kinky" d'une corde.

 

[ROXANNE]

Re: The RIGHT choice..

I seem to remember reading a couple of magazine articles in the last year or so (one of which was as result of tests by the Dashews) which indicated that Nylon is not as 'good' as it is generally thought to be, the reasons were as far as I can recall.
1. Its wet strength is something like 70% of its dry strength.
2. The effect of repeated loading/unloading causes heat build up and further reduces strength.
3 The 'bungy jump' effect that goes with elasticity can be undesirable!

I think (but may be wrong) that one or the articles suggested polyester might be a better choice?

I'd be interested to here your comments.


Derek

 

[hylas]

Re: The RIGHT choice..

Well seen Derek..

When wet, polyamide will loose aproximately 10 to 15 % of its strenght.. and you are right, wet Polyester will not loose any resistance..

When heavy loading and unloading will occurs, Waves or at least sea water spray are likely to wet the rope and therefor to cool it.
-there is nearly no "Bumpy Jump" but the shock absorbing effect of the Nylon is highly required

Polyester is a good alternative, but it is less elastic than Nylon
Polyamide: 37% at 75% of he breaking load – Polyester: 29% at 75 % of the breaking load