5/16" or 3/8" Chain

[freshalaska]

You’re not going to break G4 5/16 chain, which is 1 pound a foot and 3/8 is 1.5 pounds a foot. You want to carry all that weight in your bow. I think people error on not long enough rode. But I’m in an area where we have 21 foot tides so this becomes a big factor in rode length.

[Tin Tin]

Just as an aside, the SWL and breaking strains are all on brand new chain, after a few years use you may have lost some metal from wear/corrosion so your 5/16 may only be 1/4 (and it only needs to be one link).

[Bowdrie]

The 5/16ths G4 will be just fine for probably 99.9% (or more,) of the time.
People talk about "ultimate" conditions.
When things reach that point most failures are not from breaking chain, it's the loss of cantenary that jerks the anchor, (or rips out hardware,) and a few feet of snubber won't do much to stop that.
In those conditions a few hundred feet of Nylon on your best anchor, (with some heavy chain at the anchor for chafe,) will make the giant rubber band that allows a good anchor to maintain its hold.

[Kettlewell]

When things reach that point most failures are not from breaking chain, it's the loss of cantenary that jerks the anchor, (or rips out hardware,) and a few feet of snubber won't do much to stop that.

This is true. I have used long lengths of nylon on multiple anchors in the several hurricanes I've been in. It's hard to put out enough snubber unless it is rigged at the beginning of the storm, which most of us don't do. Once the wind gets above a certain level (30-40 knots) and the wave action starts to get bad it gets to be very hard to change out whatever snubber you have on there, so you end up letting out more and more scope. That is not always possible because of space constraints. Sure, if you know the blow is coming you can prepare ahead of time with multiple snubbers of different lengths and weights, but it becomes difficult to do once the storm is there. I know of someone that was anchored in a blow in the Bahamas on all chain. The snubber broke, the bow roller was ripped off, and the captain mangled his hand trying to keep the chain from sawing through the hull. That's why in bad storms boats are better off with long lengths of nylon attached to decent amounts of chain at the anchor end, though in reality the chain won't be doing much at 30 knots and up. All chain is great for normal day-to-day anchoring, but not ideal once the wind starts howling and the waves build.

[SVgoinCoastal]

Thank you all for the advice! Guess I'm figuring 5/16 at this point and instead of 55-65lb anchor, I'm leaning towards 45-55. I know I was originally doing this as more of a storm setup but now I'm thinking this will end up being my primary setup. Thanks again yall

[rslifkin]

Originally Posted by SVgoinCoastal

Thank you all for the advice! Guess I'm figuring 5/16 at this point and instead of 55-65lb anchor, I'm leaning towards 45-55. I know I was originally doing this as more of a storm setup but now I'm thinking this will end up being my primary setup. Thanks again yall

The 55 - 65 lb range anchor is definitely not too big. I'd say 45 is the bare minimum for most 38 foot boats, I'd rather see 55 or bigger on the bow. The weight is definitely better used there than as heavier chain.


For comparison, my 38 foot powerboat carries a 73 lb primary anchor and I've never thought it was too big.

[thinwater]

I'm confused.


ABYC H-40 table 1 list 3600 pounds SWL for a mooring and 2400 pounds for a storm anchor. G43 has a SWL of 3900 pounds. Done.


ABYC no longer list wind speeds in the table. Historically, they had listed 60 knots as mooring and 43 knots as storm. Remember, this is with ...

• No snubber.
• Above average yawing.
• Relatively shallow water, such that catenary is not very effective, but not in the impact zone.
• Long scope, no shelter.

In other words, a worse case scenario that is unlikely. In harbor and with a snubber the load will be about 2-4 times less, as measure on load cells by many testers.



Think about this another way. Can you motor into 40 knots? Probably just. What is your horsepower? 40? That's probably less than 1000 pounds thrust.


The ABYC table is very conservative. There is no need to go farther. If you expect a storm, certainly you will have a long snubber. Common sense.


---


I've done a lot of testing. The interesting thing is that doubling the size if the anchor roughly doubles holding, while going up one size might increase holding 20%.



On the other hand, the range of rode tension between my boat anchored to reach the ABYC values (yawing, no snubber, relativly shallow water, no protection) and anchored to a long bridle either in the open or sheltered was 3-5 times less. For example all chain and a 50# anchor might be equivalent to a long bridle and a 15# anchor. Yes, I tested that too.


I recall one day I was shifting from a long snubber to no-snubber for testing. I pull the boat up to disconect the snubber by hand. The load was only about 50-75 pounds on each leg, 140 pounds total. I then connected to an Amsteel bridle (to control yawing but still not stretch--testing, remember). While picking up my notebook a medium power boat wake from many miles off lifted the bow, the chain snatched, and a 2000# load cell shattered. If I had been on rope I would barely have noticed and the load would have spiked at ~ 400 pounds.



Worry more about using and rigging the anchor properly than heavier gear.

[MicHughV]

The "safe working load" for chain is a misleading number...as chain typically has a 5:1 safety factor, as has been pointed out above.
Chain can also come in different strength categories and link sizes so one also needs to be aware of that.
Correctly sized fittings between chain and anchor is another puzzle.

Finally, the attachment point on the boat needs to be considered, as if this breaks, the type of chain used will matter little.

[Kettlewell]

Guess I'm figuring 5/16 at this point and instead of 55-65lb anchor, I'm leaning towards 45-55.

As one datapoint for your consideration I have anchored with a 45 lb. Mantus M1 (an early model) up into the gusting 40 knots range in a relatively sheltered spot with limited wave action. Holding was good thick mud. The anchor did not budge, and when I pulled it up it was well embedded. The strain was enough to break our snubber, an old 3/8" nylon one tied on with my modified rolling hitch. I don't think that anchor would have moved in a lot more wind. We have never dragged the Mantus in over a decade of use. Some years prior to that our 45 lb. Bulwagga held us in the San Blas Islands on short scope with winds clocked at 56 knots. I also used a 45 lb. genuine CQR on a heavy 37 footer that we sailed from New Brunswick to Florida and back. Since we had no windlass on that boat our rode was mostly nylon with a short length of chain. IMHO a 45 lb. modern generation anchor is plenty for a 38 footer.

[mako]

Don't worry about the chain even for storms, multiple snubbers will reduce shock loads. However how about adding another 20+ lbs to your anchor. Money better spent than on bigger chain.

[derfy]

I have 5/16 on a 44' 24,000 lb monohull with a 55 lb Rocna, which holds well in 50 kts. It is really good if I have 5:1 or more scope, which often I do not.

But, I have wondered if adding weight to the chain may well increase an anchor's holding power by lengthening the amount of chain on the bottom for a given total amount of chain deployed and load. This might particularly be true in a crowded anchorage where short scopes are needed, and when waves cause the chain to rise off the bottom under load. I believe holding power is very sensitive to angle off the bottom.

It is not obvious which is better: more chain and scope (but lighter weight) chain, or heavier chain with somewhat less scope.

The other variables depth. If you find yourself often anchoring in deep water, then lighter chain or rope rode is probably best, else the weight of chain in the locker, and hauled by the windlass, is too huge. I need only 215 ft of chain for my fairly shallow coastlines.

I seriously doubt the chain will be the thing that breaks loose. First the anchor will drag, or a snubber will give way from chafe, or a swivel will break, or a cleat will give way.

[MicHughV]

As a side note to all of the above, I have often dove on my anchor in robust weather, while in the B'mas, where the water clarity afforded me the occasion to do so.

My anchor rode, on these occasions, consisted of 75'- 5/16" chain followed by about 50' of nylon rode and anchorage depths that were maybe about 15' or less.

In about 30-35 knots or so of windspeed, I was surprised to see most of the chain laying flat on the seabed, with only about 10-15' of the chain off the bottom, which would undulate up and down as the bow pitched up and down in the short chop of around 3'.

The catenary shape that the chain takes is of itself important, as before the pulling load can approach the anchor, the catenary load must be defeated.

This is hard to explain with drawing a sketch.

In the B'mas, where bottom holding is notoriously poor, swimming all the way out to the anchor would reveal that the anchor (Bruce) had only one fluke buried maybe 9" deep or so.

I have repeated this process with a CQR anchor and have also dove on other people's anchors for a looksee to satisfy my curiosity as to what was really happening below the surface of the water.

There have been several in-depth threads on this forum covering anchoring technique's, amount of scope, length of chain, different anchors, etc. and there is more to this puzzle than just how an anchor is designed or the length, strength and weight of chain.

The fact that there is a wide variety of anchors available on the market attests to the many different views taken by those anchor manufacturers, all claiming this, that or the other.

In the three boats I've owned, I've been fortunate that all of them lay docilely to an anchor with little side to side veering.
On the other hand I've seen sailboats dance around in an anchorage as to defy belief, easily veering 45 degrees one way or another, a problem that would be hard to address with just an anchor selection.

There really is no one size fits all, and a skipper may have to experiment with different anchors, rodes, etc to find a solution that best addresses that skipper's needs.

[Bowdrie]

Originally Posted by MicHughV

On the other hand I've seen sailboats dance around in an anchorage as to defy belief, easily veering 45 degrees one way or another, a problem that would be hard to address with just an anchor selection.

What you describe is quite prevalent among boats with very little hull in the water and lots of boat out of the water, (next to nothing in the way of lateral plane in the after sections).
That, along with big rolled-up jibs that produce a large amount of windage/drag in the worst place, up high and at the bow.
Boats that like to dance need some creative offset snubbing/lead of the rode to get some "angle on the bow" as it were.

[sailingharry]

I'm going to jump on the bandwagon. Like many others up thread, our 43 ft, 22,000 lb boat carries 300 ft of 5/16 g4. I sleep well.

[GrowleyMonster]

I have always felt that the chain is more important than the anchor. The anchor holds the end of the chain. The chain holds the boat. The weight of the deployed chain is important. The catenary lowers the pulling vector to near horizontal and provides shock loading protection. As others have noted, chain strength, while not irrelevant, is usually not the cause of failure. Cheechako nailed it. Failure is usually at terminal or connecting hardware rather than the chain itself.

I faced the same decision a couple years ago and I think going with 3/8" was the smart move even though I couldn't get all 400' to stack in the chain locker and had to cut off 75' of it.

You might want to try a trial loading on the bow or in the chain locker, actually, to simulate trim and sailing characteristics with both sizes of chain. Maybe weight in the bow will be a dealbreaker on the heavier chain, maybe not. But chain is expensive so it would suck to buy chain and decide you don't want it in the chain locker, and have no other practical way to keep it.