Anchor chain. Change from 8mm to 10mm ?

[sarabande]

Sara you do not need to cart a shorter length of 10mm chain carry the same weight of longer 8mm, that is more than adequate for your fine yacht
A Fortress with 3m of 8mm chain spliced to 50m x 14mm anchorplait warp

Gotta Fortress set up as you suggest, and a Knox, and Delta, and about 200m of assorted chain.


I am trying to rationalise and optimise, and finalise.

 

[lw395]

Catenary effect is non existent in a F6 and upwards, at under a F6 it's not doing very much unless in very low winds where it can stop you drifting about. 8mm gives Catenary at low and mid strength winds.

....?

If the water's not flat, the mass of the chain and its drag through the water does have an effect.
Whether the extra mass and drag of 10mm over 8 is any help? God knows.

 

[GHA]

This is a Ludite thread. Calculation, engineering standards, and facts are overrun by gut feelings and fear. I'm guessing there are few practicing engineers in the audience.

+1.
Or even a reach for a pencil and paper and Google ...

 

[thinwater]

If the water's not flat, the mass of the chain and its drag through the water does have an effect.
Whether the extra mass and drag of 10mm over 8 is any help? God knows.

I did bunch of load cell testing to do with snubbers. It helped separate fact from theory.

I think the easiest way to get solid numbers may be for someone to measure loads both ways (2 chain sizes) in a variety of weather.

Engineers measure.

 

[Chris_Robb]

For our 42 foot boat I will downsize to 8mm from 10mm when I next have to get a new chain.

Advantages - more will fit in the locker - just have 60m plus 60m warp now.

Disadvantages - will have to change the gypsy on the Lofrans Tigres.

But all the evidence says that breaking strain for 8mm is already far more than adequate, it has almost the same amound of chafe protection (any difference practically irrelevant as you would notice severe wear) and the only place where weight matters is the anchor, except in very light conditions when you have nothing to worry about anyway.

The only key thing is to have stretch not catenary as part of the set up as catenary reduces to almost no shock absorbtion in a moderate wind whether 8 or 10mm

+1 You probably have little enough space to accommodate all your chain anyway without having to push over the pile in your chain locker. 10mm chain on a 36 footer is just a waste of time.

As for Catenary action, really it has little relevance once its windy as the chain gets pulled straight in the gust. If your worried about snubbing employ a chain hook on 20 meters of 14mm nylon warp.

10mm chain has many different standard sizes, it would be pure luck if your fitted the one that your chosen winch has. 8mm has 1 (as far as I know). So much easier to get chain for it.

 

[RupertW]

+1 You probably have little enough space to accommodate all your chain anyway without having to push over the pile in your chain locker. 10mm chain on a 36 footer is just a waste of time.

As for Catenary action, really it has little relevance once its windy as the chain gets pulled straight in the gust. If your worried about snubbing employ a chain hook on 20 meters of 14mm nylon warp.

10mm chain has many different standard sizes, it would be pure luck if your fitted the one that your chosen winch has. 8mm has 1 (as far as I know). So much easier to get chain for it.

I don't think it's pure luck - 2 standard sizes with options for most windlasses for one or the other.

But like anyone who thinks about it you are right about catenery action being negligible as it's only advantage (except in very light wind) is shock absorbtion as the chain goes from a bit curved to a tiny bit curved. And once you are about 15-20 knots that's a tiny distance so as you say, a snubber with stretch is far more effective.

I happen to use a rubber snubber usually with a couple of meters of nylon warp to stop clanking and jerking in waves but have another 18m of warp to let out if conditions are such that the rubber stops being effective and the stretch of the warp needs to take over.

The concept in the post above of the chain resistance in water slowing things down is odd, like saying a hairier rope will help.

So next time it's 8mm and much more chain

 

[Neeves]

Despite there still being some evidence of gut feel and fear it is refreshing to see the increasing numbers of people rejecting catenary and down sizing their chain.

Heavier chain offers catenary - I cannot think of any other advantages that stand scrutiny - and I'm sceptical of the real advantages of catenary

Smaller chain is lighter; takes up less room; needs a smaller, so its cheaper, windlass (and the windlass needs less reinforcing); the windlass needs less power and thus smaller cables; and the chain costs less. Smaller chain Is more than sufficiently strong (post if you know of chain breaking or even stretching). If you use a decent snubber you introduce damping similar to catenary. If you desire you could sacrifice some or all of the weight saving and have more chain.

Historically, before the days of the electric windlass, many used mixed rodes - and some still do - I do not recall a desire from them to replace with lots of heavy chain.

Jonathan

 

[Heckler]

32ft Sailing boat, 6 tons displacement. Two main anchors (sized for a 36ft boat) both currently on 8mm chain.

I am lusting gently for a manual winch to ease the workload on a creaky back.

I've had a very useful progressive talk with SLSpares, the Simpson Lawrence winch man. He recommends the Seatiger, for which the smallest gypsy is 10mm., and by chance I have 60mm *** of calibrated good chain from my 36ft previous boat.


Question. Is 10 mm chain an excessively oversize upgrade choice, in order to accommodate the Seatiger winch ? I have a very conservative approach to equipment, and am happy with the idea lying to weightier chain matched to the (relatively) large anchors. Am I being over-cautious ? A third anchor (kedge) is on 8mm and will remain at that size.


*** EDIT. That is Exmoor speak for 60metres O:

My 38 ft Bene has 10mm I wish it was 8mm. My neighbour in Albufeira with a Bav 42 only had 8mm and it was fine. I have told the story about me finding an extra 30mtrs of 10mm in the chain locker attached to nowt! It made the head go down by quite a few inches. I would have spliced it in if it wasnt. I have the std 30mts plus an extra 20 mtrs but the extra 30mtrs would have been handy if it didnt make the had go down!
Stick with 8mm!
Stu

 

[PaulRainbow]

Historically, before the days of the electric windlass, many used mixed rodes - and some still do - I do not recall a desire from them to replace with lots of heavy chain.

Jonathan

All of my boats have had mixed rode, with 8mm chain. Last two were mobos and had 20m of chain and lots of rope, never had any issues with holding or chafe. I doubt the rope touched bottom as a rule, it never showed any wear. One thing for sure though, never had to worry about snubbers with 50m of nylon out

Current boat is 33 ft, probably the best part of 10 tons and also has mixed rode. According to the paperwork she has 85m of 8mm and some 14mm rope.

 

[thinwater]

My current boat (4.5 tons) came with a mixed rode. The prior boats were all mixed rode--you don't put chain on a 500 kilo, 9 meter Kevlar racing cat. When I got a new anchor (the original was too small for soft mud), I went to all-chain because the windlass did not like passing the rope-to-chain splice and would sometimes jam.

And then I learned about the irony splice, a long splice for rope-to-chain that just flies through the windlass. If I had known about it then (it was basically unknown then) I would probably have stayed with a mixed rode. Less weight. less jerking. I may yet go back to it, when this chain rusts. Yes, I'll need a little more scope, but not much more with modern anchors. A simpler bridle. The bottom around here is rock-free.

I'll post this again.
http://sail-delmarva.blogspot.com/2016/05/irony-splice.html

 

[ianabc]

- have Simpson lawrence 555 ( largest manual windlass)

- made longer windlass handle, now well over a meter ( stainless pipe hydralically squished to original handle)

- no problem retreiving in deep 25 m water

 

[thinwater]

Anyone every see testing that compares impact loads on larger vs. smaller size chain? I've seen data on rope vs. chain and on snubbers, but never comparing different weight chains. Without data this is a really difficult (repetitious) conversation.

 

[lw395]

Anyone every see testing that compares impact loads on larger vs. smaller size chain? I've seen data on rope vs. chain and on snubbers, but never comparing different weight chains. Without data this is a really difficult (repetitious) conversation.

The problem is, people can gather data as much as they like, but anchors vary, seabeds vary, boats vary. Then what depth do you pick, and what scope?
Then the big variable is wave motion.
I saw a boat anchored off the beach at Looe the other weekend, whatever anchor the had obviously works very well, but I wouldn't have wanted to be on the boat!
Any sensible person would have gone elsewhere. Analysis of the motion of the chain would not have been my top priority, but it was interesting to think about from the beach...

Some people sail in areas where there may be no option but to sit out gales on the hook. Many of us have more harbours than anchorages to choose from.

 

[charles_reed]

Was there much difference in the boat sailing about at anchor afterwards?

Though he doesn't stress it Jonathan's boat is a catamaran.

I have noted that catamarans, lying to a textile bridle are infinitely more stable and unlikely to shear around than monohulls, especially in winds >Bf 5.
that wind force is, incidentally, where the chain catenary has disappeared.
Putting 3-10m of nylon Octoplait in the rode has seriously reduced this tendency on my boat - instead of sheering through 100 degrees it has dropped to about 45.

 

[PaulRainbow]

I went to all-chain because the windlass did not like passing the rope-to-chain splice and would sometimes jam.

I've always used a back splice with 3 strand nylon and 8mm chain. I found that a tapered splice didn't jam. I use the same tapering technique with my mooring lines. I make the required number of tucks first, then make an extra tuck. Snip off 1/3rd of each strand and melt it to the remaining 2/3rds. Make another tuck and snip of 1/2 of what's left and melt it to the final 1/3rd. Make a last tuck and carefully melt this to the standing part of the rope.

The welds need to be done with care, you don't want to melt and weaken the main line. If they are made on the underside every time they can't be seen and it's a very neat splice.

 

[charles_reed]

I agree about the effect of weight in the bow, which will be a really big, maybe overwhelming consideration for small, good-sailing boats.

For casual "chucking the hook", though, use your kedge! A Fortress on rope, not chain.

In fact, though much heavier, a steel Danforth works just as well as a Fortress (or Guardian). The problem with all those anchors is that they frequently do not re-set, if there's a change in direction of pull. In fact Fortress recommend a short length of chain between anchor and textile rode.

 

[Chris_Robb]

Despite there still being some evidence of gut feel and fear it is refreshing to see the increasing numbers of people rejecting catenary and down sizing their chain.

Heavier chain offers catenary - I cannot think of any other advantages that stand scrutiny - and I'm sceptical of the real advantages of catenary

Smaller chain is lighter; takes up less room; needs a smaller, so its cheaper, windlass (and the windlass needs less reinforcing); the windlass needs less power and thus smaller cables; and the chain costs less. Smaller chain Is more than sufficiently strong (post if you know of chain breaking or even stretching). If you use a decent snubber you introduce damping similar to catenary. If you desire you could sacrifice some or all of the weight saving and have more chain.

Historically, before the days of the electric windlass, many used mixed rodes - and some still do - I do not recall a desire from them to replace with lots of heavy chain.

Jonathan

Jonathan - its arguable that the heavier the chain (especially the use of an anchor chum) the more the yacht rebounds to windward after a gust has passed through, -the extra weight of the chain pulling the boat forward faster- , just exaggerating the antics of the yacht. The use of a long snubber takes all the energy out of the movement as so perhaps reduces the extent of the movement. I have not sufficient experience to say whether this works. It is just a theory

 

[Neeves]

Disliking the maths, or not finding that it had the visual impact, I looked at an actual catenary.

I took 30m of 8mm short link, our (then) anchor chain which was actually 50m but I only had room to work with 30m - I measured out height and length and suspended the chain so that the bottom link was just off the ground and the top of the chain made a 5:1 scope. Load cell measurement of the tension at the top, or where the bow roller would be was 78kg. This of course is in air and in water the tension would be about 68kg (some of the chain would still be in air). To put this in context - this is the sort of tension a reasonably fit male can produce (or hold) in the same chain.

I'd previously measured the tension of a similar length of chain at a similar scope in wind and a tension of about 68kg is equivalent, for our catamaran, to a wind speed of about 17 knots and I chose the location to be effectively wave free - the cat was simply subject to wind. I measured this with a Dyneema bridle - I was looking to measure tension without elasticity. The windage of our cat is similar to a Bav 45, but we weight in at 7t and a Bav45 about 12t.

As Charles mentions a cat on a bridle will move differently to a mono hull and if the mono is more frisky those weight differences will come into play. If you have a mono - if you can rig a snubber(s) as a bridle you would find it advantageous as you will further steady the yacht (over a single snubber) - and its 'sailing' at anchor (and waves) that develops snatch loads - not wind speed per se.

I'd say that at 30 knots, same chain, same scope etc the chain 'looks' straight (its not but as good as) at about 30 knots.

These are ball park figures - all the figures are as measured but there are lots of variables. For other yachts of a 'similar' windage, that Bav45 for example, the tension might be higher or lower at 17 knots - but its in the 'right' area. One problem is you never get wind at a fixed speed of 17 knots, its constantly varying (in both directions and speed) and the yacht is constantly moving.

Any idea therefore that friction of the chain on the seabed has any impact over, say average 25 knots (when the wind might vary between 17 and 30 knots), needs to be re-thought. Obviously if the chain is longer or heavier the data changes - but not by much - when you consider its 'square of windspeed'.

What I found of most interest was the very low wind speed at which all the chain was lifted off the seabed. I had fondly imagined the chain and friction to be of value - the reality is that piano wire, if it were sufficiently strong and corrosion resistant (and Vyv alluded to this earlier) would be as useful as the sort of chain we can sensibly carry. You can carry more chain, you can carry heavier chain - but most of us have 'smaller' yachts and there is a finite limit to chain weight and length. Snubbers offer 'impact resistance' (one of the benefits of the heavier chain) and they are cheaper and lighter than steel.

Jonathan

 

[Fr J Hackett]

If the water's not flat, the mass of the chain and its drag through the water does have an effect.
Whether the extra mass and drag of 10mm over 8 is any help? God knows.

I suppose you could resolve the force of the wind on the boat into one horizontal vector, then the force created by the weight of the chain regardless of wether it's bar tight or not into another and opposite vector. subtract one from the other would allow a comparison of the two types of chain for a constant wind force would then tell you the effectiveness of 10mm over 8mm chain.

 

[doug748]

Despite there still being some evidence of gut feel and fear it is refreshing to see the increasing numbers of people rejecting catenary and down sizing their chain.......

I doubt it.
What you see is a tiny fraction of the small number of sailors who warble on this stage, being swayed by a highly particular argument.
The majority forum members are just reading smiling or frowning, probably thinking WTF does it matter?
The mass of sailors have little idea the forum exists.