Cruising Anchor Chain Length

[Lost Horizons]

Originally Posted by CAVOK

Hey thanks for all the information. I didn’t think it would stir up this much discussion. Can I ask whether keeping extra chain separately stowed for deeper water anchorages is a good idea. It would allow me to put the extra weight in a better position, but I am concerned about the relative strength of the joiner. Is there a best/strongest way of doing this.

It may be a good idea, particularly if not exercised regularly. For instance, I have 350’ chain for the primary rode and 90’ chain + 300’ rope for the secondary with the possibility of joining them if needed. The strongest way is to use two shackles sized such that the pins tightly fit the chain link apertures. With this configuration I can anchor in a 100 feet of water with a decent scope, or in 200 feet with half-decent scope if needed.

[Dockhead]

Originally Posted by daletournier

I'll just add one more thing, you mention that inevitably when cruising the world you will anchor in 30-40m at some stage, I disagree.

Most boats are just not equipped for that depth therefore they dont and they still manage to circumnavigate. You do, because you can.

The other problem with anchoring in that depth is it's almost impossible to know if your dug in well, backing down on your anchor takes on a new meaning when trying to stretch that amount of chain out and feel see that its holding well.

In the few occasions where I've only had those depths as a option without practically being on shore (think sides of volcanoes) I move on, even if it means staying out to sea heaved to to rest.
... . .

Well, you can only do what you can do, of course.


But I would add that there are places where it is crucially important to be able to anchor in 30 or 40 meters of water, because there simply isn't any feasible anchoring anywhere else.


These are areas with steep-to shores and steeply sloping bottom. You can't anchor in a steeply sloping bottom - you need something flattish and sometimes the only flattish bottom is in the deepest place in a cove or bay.


I know this is an extreme example, but the most striking example of this which I have encountered was in Scorseby Sund in NE Greenland. This is a huge fjord system which goes back a hundred miles or more into the interior of Greenland. There are ZERO harbours in there, ONE more or less decent anchorage near the mouth but without any shelter at all from S to W, and beyond that you are on your own to scratch out something between the cliffs and glaciers and icebergs. The shores are very steep-to and the water is often 30 meters deep just 50 meters from the shore. You are lucky to find any place you can get your hook into at less than 30 meters, and I anchored in as much as 50 meters.


Going out to sea and heaving to is not an option, because there is ice in the water. Finding a harbour is not an option -- the nearest one is 500 or 600 miles away. Shore tie is really the only alternative, and for that you need special long ropes.



On a lesser scale, though, you can find similar situations in Norwegian, Swedish, Finnish waters, Faroe Islands, etc.


So depending on where you are sailing, 100 meters of chain may be the absolute minimum and you will have real trouble if you don't have it.


But I agree that on a normal circumnavigation, where there is sand almost everywhere, it's more likely to be possible to do without.

[daletournier]

Originally Posted by Dockhead

Well, you can only do what you can do, of course.


But I would add that there are places where it is crucially important to be able to anchor in 30 or 40 meters of water, because there simply isn't any feasible anchoring anywhere else.


These are areas with steep-to shores and steeply sloping bottom. You can't anchor in a steeply sloping bottom - you need something flattish and sometimes the only flattish bottom is in the deepest place in a cove or bay.


I know this is an extreme example, but the most striking example of this which I have encountered was in Scorseby Sund in NE Greenland. This is a huge fjord system which goes back a hundred miles or more into the interior of Greenland. There are ZERO harbours in there, ONE more or less decent anchorage near the mouth but without any shelter at all from S to W, and beyond that you are on your own to scratch out something between the cliffs and glaciers and icebergs. The shores are very steep-to and the water is often 30 meters deep just 50 meters from the shore. You are lucky to find any place you can get your hook into at less than 30 meters, and I anchored in as much as 50 meters.


Going out to sea and heaving to is not an option, because there is ice in the water. Finding a harbour is not an option -- the nearest one is 500 or 600 miles away. Shore tie is really the only alternative, and for that you need special long ropes.



On a lesser scale, though, you can find similar situations in Norwegian, Swedish, Finnish waters, Faroe Islands, etc.


So depending on where you are sailing, 100 meters of chain may be the absolute minimum and you will have real trouble if you don't have it.


But I agree that on a normal circumnavigation, where there is sand almost everywhere, it's more likely to be possible to do without.

I just would not go there.

I would suggest most cruising boats are just not equipped to anchor safely in those depths. If you intentionally plan to anchor in those areas then sure, but you need to set up the boat specifically to do so.

Most crusing boats (and it's a big most) would have windlasses that would struggle to pull anchor and chain straight up from depth of 40 m, yes there are exceptions but not common. Secondly a large boat with a large locker is required to store amount and size of chain nessacary for these depths, not all have a 50ft plus boat. You foul in 40m that's a deep short dark dive.

In 12 years cruising around the world I've only needed to anchor in 20m+ plus a handful of times and this includes the ring of fire area Indonesia which is extremely volcanic .30-40m is a rare exception far from being normal while cruising the normal routes that most do.

[Sailing4Jesus]

All this discussion reminds me of The Manual for my MERCEDES BENZ 320 CDI AMG, The German who wrote it says to go to page 9, you get there and read one or maybe two lines, then you are directed to another page, then another, and another, and perhaps a few hours later you might know how to adjust the time on the Car Clock. Yes, it was a Nightmare. I gave up the first year and just left the Dad-Gum Clock be. But man oh man what a wonderful car the Mercedes Benz.

[s/v Jedi]

For linking chain you can get these. They maintain link spacing and are as strong as the chain (G7 marking is visible) but they are not galvanized. I spray them with zinc every time we’re doing maintenance on the anchoring system

[Pete7]

Nick, that looks neat, do you have a link for the link?

Looks like a split pin to hold the pins in is this correct, if so should be quick to fit rather than bashing nodules on a C link together.

Pete

[RickG]

We just upgraded the ground tackle for our 43' 12-ton boat in the Caribbean. We went from 200' BBB 3/8" to 300' 5/16" G4 HT. The chain weight in the bow went from 480 lbs. to 311 lbs. We moved from an old Simpson Lawrence 1500 watt windlass for which there is no 5/16"/8mm gypsy to a Maxwell HRC10-8 windlass; we stayed with a horizontal winch due to space constraints in the anchor locker and it keeps the motor out of the chain funk. We updated our snubber to make it longer and heavier and replaced the old Mantus chain hook with the new one. We kept our 25kg Rocna, Mantus Anchor Mate, and Norestar chain stopper.

Why not go big with more chain and a bigger anchor? Weight and lack of need. We have a relatively light production boat and she's not happy heavily laden. Our 25kg anchor holds just fine in 50 kts clocking around the compass.

After safety, the most important thing for us is keeping the Admiral happy. She refuses to be on the helm when anchoring. She did not trust the old occasionally balky windlass or the chain that had a bit of rust on it. We added a chain counter and a remote in the cockpit. She is very happy. I reminded her that I spent more on her ground tackle than on her jewelry; she'd rather have new ground tackle.

Note to the CAVOK, you may get a better price if you buy a full or half-drum. For Acco 5/16" G4 that would be 550'/275'. For Acco 3/8" BBB that would be 400'/200'.

Cheers, RickG

[argonauta1]

Circumnavigation 1998 to 2008. Yacht 45 Ft. Two anchors mounted at bow: Main: CQR 45 Lb with 200 ft chain 3/8" backed by 100 ft line. Secondary Bruce 33 Lb with 30 ft chain and 150 ft of line. Stern Bruce 33 ft 30 ft chain and 75 ft line.

Must not skimp and be prepared to anchor in as much as 80 ft. (Moorea). Plan on scope of 5/1 not 3/1. You always need 5/1 in a wind storm. There will be many! Also note that 175 feet of chain is not nearly enough for 80 ft depth. Even 175 chain and 100 ft line is barely sufficient. Must get this right or you risk becoming a beach ornament!

Incidentally, charter yacht operators in Tahiti (Raiatea) carry 60 ft of chain backed by 350 feet of line.

[conachair]

Originally Posted by argonauta1

Plan on scope of 5/1 not 3/1. You always need 5/1 in a wind storm.

Remember the catenary effect works different at different depths, 30m + 3 x depth isn't too far out for deeper water for 10mm chain assuming you want to just lift the last link with 500Kg horizontal load.

https://www.desmos.com/calculator/mpbs9et8ta.

[reflectionsv37]

I agree with the others that you want at least 300'. I carry 350' on a 37' boat. I actually prefer to anchor in water a little deeper 25-30' so with 5:1 scope I end up anchoring using 150' most of the time. Having all that extra chain, in addition to the obvious benefits, also allows me to double the life of my anchor chain.

I like to end to end the chain about once a year so I don't end up with 150' of new chain sitting below decks never used. When I first started cruising I had 225' and that handled my anchoring okay, but I still flipped my chain once a year and ended up with chain that was still usable on each end and rusted and unsafe in the middle. Now I end up with very lightly used chain in the middle that is usually wrapped around the windlass. It allows me to also cut off 10' feet on the ends to extend the life when needed.

[Perfect Ride]

Originally Posted by CAVOK

Is there any consensus about what is the ideal anchor chain length to carry on a cruising yacht. We intend to cruise the Med then over to the Caribbean and possibly further, so there isn’t any specific cruising area. I intend to have only chain as I will be anchoring out as much as possible. Ideally the more the better, but cost, weight and it’s distribution also have some bearing. Thought there might be some long-term cruisers that may have an opinion based on experience.

100m chain with 70m triple braid: We are on only chain 98% of the time, but on more than one occasion the additional scope in 40m+ depths was the best of other available options. We also carry 100m of floating line for tying off to land that we use more than the triple braid. For perspective : this setup has been used over 5 years in Med, Atlantic, Carib, S Pac. We are 95% at anchor vs dock.

[FranklinGray]

I may missed it but it seems these post are a bit weak on the details that make up the outcome of anchoring. It is a combination of type and size of anchor, water depth, current, windage, waterlevel wind speed (wind protection), weight of chain, weight of boat and size and depth of waves. However, the most simplistic version is size of boat and weight of chain dropped and anchor used.

AKA...a 40' boat with 5/16th chain will need more chain out then a boat on 3/8th chain. Notice I am not talk about water depth or scope. Scope is totally misleading. a 7 to 1 in 10' of water is only about 70 lbs in 5/16th, but 4 to 1 in 50' of water with 5/16th is about 200 lbs. It is the weight of the chain that determines pull direction. It is a lot harder to straighten 200 lbs verses 70 lbs. So this talk about chain straightening in 35 knots of wind is misleading; that depends on how much chain is out and weight of the chain and size of the boat.

It tight anchorages with deep water, you can use a trick of having a long snubber line and then let out a lot of chain after the snubber to add weight to help keep it down.

I am currently using a light chain 3/8th for 55' boat but with just a 3 to 1 scope my 105 lb Mantus holds just fine in 35 knots of wind at 35 feet deep. I wouldn't dare use 3 to 1 in shallow water, especially with this light chain.

Now on to the OP's question: I wouldn't think of going to the South Pacific without at least 80M of chain and another 30M of rope on the end of it. I went with basically that on my last boat and had no problems but at times I had to use moorings. With this boat I hope to have 100M of chain.

[Dockhead]

Originally Posted by FranklinGray

It is a lot harder to straighten 200 lbs verses 70 lbs. So this talk about chain straightening in 35 knots of wind is misleading; that depends on how much chain is out and weight of the chain and size of the boat.. . .

It is certainly true that the weight of the chain directly affects how much force is required to straighten it. I think everyone understands that.


However, I think every single realistic cruising boat combination of chain will be bar tight in 35 knots. It might have taken longer to get there for a lighter boat with a heavier chain, but by 35 knots virtually every boat has gotten to a bar tight chain.


35 knots is well over a tonne of force on a 54' boat (using the ABYC table). It only takes 500kg of force to lift the last link of 100 meters of 12mm chain off the bottom, to use my boat and my chain as an example.


You can play around with any given set of variables here:


Tuning an Anchor Rode

[FranklinGray]

ABYC table is way overestimating it. Try the formula: .00256 x sq ft of wind age x kts squared x drag (2 for flat surface, 1.4 for round pole)

[daletournier]

Something else to consider is that many modern monos can really yaw around at anchor ,the nose blows off back and forth which pulls the chain tight, they can snatch quite violently at times.

I find that cats may not yaw as such but they do sail around alot.