Deep anchorage experiences?

[LoudMusic]

Hey I'm looking at possibly anchoring in 65 feet of water next summer. We have 200 feet of chain and what I'm seeing online (in particular DSII video) people are indicating the deeper the water gets a smaller ratio may be acceptable. I'd be getting around 3:1 on that. I think I'd be more comfortable putting another 200 feet of nylon on the end of that, but we'll see.

What experiences have you had with deeper water anchoring? What were the conditions and what hardware did you use?

[chouliha]

Years ago we spent 2 seasons out in Socorro island Mexico. A good portion of that time we spent anchored in 95’ of water. We carry 300’ at the time and had about 280’ out. No big wind events just swell. No issues except our windlass took awhile to crank it all in. You should be fine with what you have if it’s not stormy.

[LoudMusic]

Originally Posted by chouliha

Years ago we spent 2 seasons out in Socorro island Mexico. A good portion of that time we spent anchored in 95’ of water. We carry 300’ at the time and had about 280’ out. No big wind events just swell. No issues except our windlass took awhile to crank it all in. You should be fine with what you have if it’s not stormy.

So far I think the deepest we've anchored in was probably 20', but typically less than 10'. I kept thinking we had the best windless ever because it didn't struggle at all. After researching deep anchoring I started realizing why they make them so tough!

[jrau18]

If you are all chain, it's true that a lower scope can work the deeper you go, up to a point. This is because of the caternary effect of the chain. All that weight means that when you're really yanking on the anchor, the angle it pulls on the anchor itself may be the same angle as a longer scope with all nylon would be.

Imagine a heavy pull on the anchor in 8 feet of water. If you're at 3:1 ratio, your boat will lift up all that chain, since its only maybe 50 pounds, so there is almost no difference between nylon and all chain rode at a shallow depth like this, so you need to pay out more chain as if you had only nylon rode, maybe 7:1 or so.

But now imagine in very deep water. You could have hundreds of pounds of chain down, so the effect of the chain is greater. For a given amount of force on your boat, the angle on the chain at the shank of the angle will be much lower than you'd expect from the same scope with only nylon.

So for very shallow anchorages, you need a higher scope with all chain, the same as with nylon. For very deep anchorages, 4:1 or even 3:1 (with very heavy chain) might develop the full anchoring force of the anchor. Depths in between of course would be in between.

In the scenario you describe, I'd consider putting out some extra nylon rode if you expect any potential weather, I dont think you have enough chain alone. I would shoot for 4:1 or even a bit more. If you use about 70 feet of nylon, that should keep only chain on the bottom in your situation while providing a little more security if it picks up in the night.

[GRIT]

We never had an issue at 3:1. 30kg Genuine Bruce, all chain (8mm), on a Corbin 39. That was our standard scope, and never more than 5:1. (Hurricane Juan was an exception)

Horses for courses.

Cheers.
Paul.

[CassidyNZ]

Anchoring in Fiji (our preferred cruising ground), the depth is often up to 20 metres which I think is 65ft. We have 40m of 10mm chain and 60m of nylon in our rode.

At that depth we mostly put out all the chain and half the rope (3.5:1 scope). The trades in Fiji in winter regularly run at 20 to 25kn and many anchorages are protected from swell but not so much from wind and we have never dragged once. And we have one of those “useless” CQR anchors as well.

Having said that, I’m adding 20m of chain to the main anchor for next season.

[Recy]

Originally Posted by CassidyNZ

Having said that, I’m adding 20m of chain to the main anchor for next season.

How will you join the chains?

[bwindrope]

Cruising in the Salish Sea here in the PNW sometimes requires deep anchorages since our entire area was glaciated and the depths are often 500 or more in the channels. Teakern Arm in Desolation Sound requires dropping in 70 feet and stern tying, so that is a bit different. There is an anchorage along the Vancouver island shoreline called Deep Bay and you will drop in over 70 feet. My experience has been like others have said, that in fairly benign conditions and especially with a modern anchor design, you will have no problem with 3:1 if all chain. But as per usual, if there is swell or winds over 20, you are likely to wish you had the ability to go 4 or 5:1, but you wouldn't need more chain, only appropriately sized nylon.

[Neptune's Gear]

Deepest so far was 46m. Thats about 154 feet. In Banda in Indonesia. That was the shallowest available!
Our cruising chain is 110m of 10mm, and in this case we added the 2nd chain (30m) and another 30m of nylon rode. Anchor is a 20kg Rocna.
That night we had another 40ft mono rafted up as he did not have sufficient chain to anchor. Of course we had a squall come through, up to 40 knots. The anchor held both of us, be we were ready to cast off the other boat!

[alctel]

I used to anchor all around BC with 210ft of total rode (60ft of chain, the rest nylon rode). Never had any problems up to around 70 foot. Aside from pulling it all up again as I didn't have a windless. That sucked.

I don't tend to go over 3 to 1 scope anyway even in shallow water, as with a mantus it seems to hold very firmly. The couple of times I've been in over 30 knots I've let out scope to around 4 or 5 to 1.

[Dockhead]

We had an intense discussion about this some months ago.

It's kind of received knowledge that you need less scope in deeper water, yet, we were not able to figure out any valid technical reason why this should be so.

But I am generally happy with 3:1 with my setup in 15m or more of water, even in strong conditions.

I often anchor in deep water for different reasons. In rocky glaciated places like the Finnish archipelagos, you often have to go deep to find something to get your hook into. I like the deepest bit between circles of islands - that's where the silt collects. Just spent a couple of nights in just such a spot, in 18 m of water, and very secure.

[JPA Cate]

Originally Posted by Dockhead

We had an intense discussion about this some months ago.

It's kind of received knowledge that you need less scope in deeper water, yet, we were not able to figure out any valid technical reason why this should be so.

But I am generally happy with 3:1 with my setup in 15m or more of water, even in strong conditions.

I often anchor in deep water for different reasons. In rocky glaciated places like the Finnish archipelagos, you often have to go deep to find something to get your hook into. I like the deepest bit between circles of islands - that's where the silt collects. Just spent a couple of nights in just such a spot, in 18 m of water, and very secure.

You canny dickens, you!

Good strategy.

If the OP is thinking about the deep south Pacific anchorages, having more nylon back shouldn't be a problem. But you don't want it to extend to where reefs (stone or coral) are, because then chafe is an extreme problem.

People will tell you to not add chain via using a connecting link, but it has worked well for us for over 30 yrs, except for ONE time. If you run a dyneema line in a "chain splice" for 3 feet on each side of the connecting link, I think it will do you just fine, for as long as you cruise.

Ann

[Alan Mighty]

Originally Posted by Dockhead

We had an intense discussion about this some months ago.

It's kind of received knowledge that you need less scope in deeper water, yet, we were not able to figure out any valid technical reason why this should be so.

You've read Wm G. Van Dorn, _Oceanography and seamanship_, NY: Dodd, Mead & Co., 1974?

Van Dorn covers deep water anchoring on pp. 405ff, especially around Figs. 151 (p. 409) and 154 (p. 419).

If I had a day or three of free time, I'd re-read VD. It requires considerable attention.

I reckon you'll find your answer there. Should you be in port, I'd lend you my copy; it's jolly heavy and contributes to a list to starbd.

[Chotu]

I feel like a weirdo!

I'm always at 10:1 unless the anchorage is crowded. I was a bit nervous at 5:1 in a very crowded anchorage last week when a storm at about 40 knots blew through.

For deeper anchorages, I usually add nylon to maintain around 8:1-10:1.

Reading this thread, I guess it's overkill.

[CatNewBee]

I use almost always at least 5:1, deepest was 15m with 60m of chain, because we have no more, just about 40m of nylon rode attached to it just in case... .

Usually we prefer to anchor in 5...10m to be away from breakung waves, but not too deep to be able to dive and recover the anchor if necessary. We try to not anchor in deep water.