Using 3/8" vs 5/16" Chain in a Windlass

[bruce smith]

If someone made chain of aluminum, like Fortress anchor material, strong, would not break, would y' anchor yer boat with it?

[klem]

Originally Posted by bruce smith

If someone made chain of aluminum, like Fortress anchor material, strong, would not break, would y' anchor yer boat with it?

Sure, I would. If it was aluminum, I would be worried about fatigue but I personally would be totally comfortable with something even lighter as long as it is strong enough. Look at all of the performance world cruisers out there these days with G70 chain. The only reason that I don't like the idea of a mixed rode is chafe. The line is much stronger and lighter but its strength drops rapidly with chafe. For my current boat, I have a mixed rode because I feel that it is much better than carrying a few hundred pounds of chain in the bow but it is a small boat.

Another way to look at it is to compare an extra 10 pounds of weight in the anchor versus an extra 10 pounds of weight in the chain. Which would you pick if both had a high enough working load limit? I would put the weight into the anchor any day since you wouldn't even be able to tell the difference between the two chains.

[SV Liberty]

Thanks Klem, I'll check out the catenary calculators - never heard of that one. We don't really have trouble anchoring. We use a 25 kg Rocna on our Morgan 41 Out Island, along with 225 ft of 5/16 HT chain and another 175 feet of 5/8 rode (I think its 5/8, may be 3/4). Its actually been a long time since we dragged, and back then it was mostly on a 20 kg Bruce (with significantly less experience and often poor technique).

[maarty10]

For a 33 ft boat there is -in my humble opinion- no advantage to switching to 3/8 from 5/16. The amount of scope you deploy is the most critical element in anchoring other than the type of anchor used. You will be able to carry more 5/16 than 38.

The great advantage of chain other than strength is the weight; it will usually not be stretched into a straight dimension. However in very strong winds, and depending on how much scope there is, it can go fully straight. This is a bad thing. It is at this point, from the shock load on the anchor, that the anchor becomes most likely to dislodge.

On my boat -Morgan 34- I set a 40ft 1/2 nylon anchor line with a grab hook onto the main anchor's chain. Then I let out additional chain behind that without letting the loop of chain touch the bottom. The nylon anchor line acts as a snubber; it stretches under load and protects the chain from shock loads.

Optimal scope is 7 to 1. 10' depth = 70' of rode. It's not always possible, but it is something to strive for.

The cheaper price of 3/8 is false economy. Ground tackle is the cheapest insurance that you can have. You should have at least 3 anchors, preferably of different types. I carry a 35lb cqr on 150' of chain, a 33lb bruce on a 35' chain lead with 150' 5/8 rode and a 23lb fortress on 20' chain with 100' 1/2 rode. I also have a 25lb cqr as a spare.

I almost always dive on my anchors and set by hand.

I have rarely dragged anchor.

[foggysail]

Originally Posted by bruce smith

Breaking strength of chain? Even strong chain has low numbers compared to wire or nylon of comparable size.

1/4"HT (G4) chain has enough capacity with a working load limit of 2600#s to do heavy damage to most bows found on production boats. 5/16" 's working load of 3900# certainly can cause bow destruction before the chain fails under full working load. Three strand and braid? There were studies on failures of these lines used for moorings in the aftermath of Hurricane Bob that passed through local harbors in Massachusetts. The tests indicated internal heat generated under strain especially at bends resulted in line failure.

I use almost 200' of 5/16HT coupled with a swivel to an 88# Delta anchor. I do believe ground tackle is important. Good chain and a HEAVY ANCHOR are essential. I for one wnat my boat to stay put when anchored.

Foggy

[maarty10]

Originally Posted by bruce smith

If someone made chain of aluminum, like Fortress anchor material, strong, would not break, would y' anchor yer boat with it?

Nope.

Aluminum is more vulnerable to abrasion than steel. The weight of steel is an advantage because the weight makes the chain lay on the bottom. As the horizontal force of wind and tide push the boat the chain lifts from the bottom. As long as the chain does not fully straighten it acts as a dampening force; the weight of the chain also allows the pull on the anchor to be on a shallow angle. Anchors are most effective when the pull is horizontal.

Steel chain is the best and most relied upon anchor rode choice of most of the worlds serious cruisers.

[cfarrar]

If someone made chain of aluminum, like Fortress anchor material, strong, would not break, would y' anchor yer boat with it?

Absolutely. I'd put some of the weight savings into a bigger anchor and pocket the rest.

(assuming "magically" light chain... nobody would make chain from aluminium)

[maarty10]

Most anchors work because of their design. They are designed to have greatest resistance to break out when pulled horizontally. The more vertical the pull the less resistance an anchor has imposed upon it, and the less it can profit from it's design. A heavier anchor is more effective not necessarily from it's weight, but from its larger surface area, plus it is stronger.

An aluminum chain would lift more than steel -causing more vertical pull- and it would shock load more readily. It would be a poor choice even with a heavier anchor.

Anchoring is a system; it is a society of parts that work together. Each of the components need to be considered.

[cfarrar]

Maarty: This topic has been (over)debated in multiple anchoring threads. Here's one example: Anchor Chain

We actually agree on this one - we both use 5/16" chain (I have a 25 Kg Rocna on the end). So, not to be argumentative at all, but here's another way of looking at the question:

1) Catenary is negligible when it's blowing stink.
2) Therefore, the rode's angle comes from scope.
3) A larger (heavier) anchor has more surface area and holding power.
Conclusion: in a blow you'll benefit more from a bigger anchor than from heavier chain.

So, that's why I recommend that the OP stick with the 5/16" chain (especially since it might cost money to upsize his windlass gypsy to 3/8"). If he wants more holding power he can always get a bigger anchor.

Would I really want a magical, weightless chain? Well, maybe not, but here's a different test. If money were no object and I needed a significantly stronger anchoring system I would: 1) get a larger anchor (Rocna or similar), and 2) upgrade my chain to G70. This would be far more effective than buying 300ft of 1/2" BB chain.

[maarty10]

Carry anchors as large as you can handle. Use chain on the main one. Catenary is only negligible when the chain is fully straight. I don't think a big anchor on short scope is better than one a size down on longer scope.
A 55lb Rocna is a rather heavy anchor, and 5/16 chain is strong enough; I think your system is excellent, but I would not bank on aluminum chain and a heavier Rocna. Like you said: catenary is negligible in a heavy blow. Catenary on an aluminum chain would be a fraction of that of a steel.
Loss of catenary should be kept to a minimum to avoid the shock loads that accompany it.

[bruce smith]

Okay, all of you who would, theoretically, choose lightweight (alloy) chain, who among you uses 1/4" 7x19 cable? plenty of comercial BCfishing boats do. And I've seen a coupl of Canuk yachts using cable in lieu of chain.
As an aside, I have never suggested that one use a smaller anchor because the chain was notched up one size.
Also, A cruising boat that is carrying 200' of chain , 3/8 or 5 /16, should not BE carrying it all the way fwd, but dropping it aft to at least the mast step. Most windlass' are mounted too far fwd.

[maarty10]

Interesting. I wonder what depths they are dropping anchor in. Could it be that these commercial boats are setting a large amount of scope, and that the weight of chain for more extreme depths would be prohibitive?

[foggysail]

Originally Posted by cfarrar

I'd put some of the weight savings into a bigger anchor and pocket the rest.

RIGHT ON!!! And Bruce anchors will not hold well in ell grass. Here in Massachusetts I used to use a 44# Bruce on my 30' Hunter sailboat. It worked for years until ell grass dominated the area. Now in ell grass, I found the Bruce just picks up 75-100#s chunks of bay bottom. ONe can be mislead to believe it is holding until either the boat is backed down under power or a good strong wind comes along. Strange how many of the older anchors are still found on boat bows such as the plow and the Bruce.

Foggy

[zeehag]

on a 33 ft boat, 3/8 is overkill to max and will only keep your bows down. i will not fit into a 5/16 gypsy.
41 ft boats need 3/8, especially if heavy , as are morgans and formosas...i plan on upgrading to 3/8 and a heavier windlass- mine is rated only 1000 pounds...
is electric-- willing to trade for sea witch simpson lawrence manual......planning on adding one, but if a trade comes up i will fly onto it...LOL...

[landonshaw]

Ok, thanks for all of the replies. First, I am in Grenada and sail the local islands. Which means coral is a possibility. I will stay with 5/16 chain, currently I have 150 ft. I am looking to add for those times I am in deeper water and want more scope.
So your thoughts on:
100 more ft of 5/16 chain
or
100 to 150 of rope.
If rope, suggestions as to what size and how is it attached to the chain so that a weak point is not created?
Thanks for all of your suggestions!!! Dave