Anchor chain scope, double the depth?

[ramblinrod]

Originally Posted by sailorboy1

The thing with scope ratios is that they don't take into account anchor type, weight, and holding. But far as practical I have found it rare to be able to put out more than 4:1 just due to other boats and swing room.

What do people do in a crowded anchorage with little room do when a front is coming in and there isn't room for using more scope?

If any kind of wind is expected,
Put out a second anchor.

[S/V Alchemy]

Originally Posted by Vasco

It's better to be out there bouncing around with a bit of sea room rather than in a crowded anchorage waiting to drag or to be dragged down on.

This. Assuming it's a front and not a multi-day event, I would prefer to be upanchor and motoring in the open roadstead or hove to in 100 metres rather than dodging loose boats too close to a lee shore. Hence the term "weather eye, keeping out one of".

[barnakiel]

I always use what we have and this is 100 ft of chain. The rest of our rode is rope. Less if there are obstacles / other boats / etc.

water 10' deep? = 10:1
water 20' deep? = 5:1
water 50' deep? = 2:1
water 100' deep? = looking for a shallower spot!

So what if 2:1 is fine in deep water. 50 ft is not deep water. 100 ft hardly is.

Is 200 ft deep water? Well. Presumably. But none of the boats I have sailed had 400 ft of chain, not even the maxi ones that will anchor deeper than other craft (because they have huge ribs and relevant outboards),

Pragmatics, mates. Pragmatics.

I think 2:1 may be OK in deep water. Just show me how many cruisers anchor in deep water.

Love,
b.

[Sailmonkey]

Originally Posted by ramblinrod

If any kind of wind is expected,
Put out a second anchor.

Only for a hurricane.....IMHO, if you need a 2nd anchor to secure you in any kind of wind, you need a better primary anchor.

[jkindredpdx]

Originally Posted by barnakiel

I always use what we have and this is 100 ft of chain. The rest of our rode is rope. Less if there are obstacles / other boats / etc.

water 10' deep? = 10:1
water 20' deep? = 5:1
water 50' deep? = 2:1
water 100' deep? = looking for a shallower spot!

So what if 2:1 is fine in deep water. 50 ft is not deep water. 100 ft hardly is.

Is 200 ft deep water? Well. Presumably. But none of the boats I have sailed had 400 ft of chain, not even the maxi ones that will anchor deeper than other craft (because they have huge ribs and relevant outboards),

Pragmatics, mates. Pragmatics.

I think 2:1 may be OK in deep water. Just show me how many cruisers anchor in deep water.

Love,
b.

Is that when you use all your chain and just add rope to get a sufficient length for a comfortable ratio?

[Rhwins]

Don't forget to account for tide in areas with it. Here in SOCAL, its about 5' of difference between low and high tide.

[classic1899]

wow
i hope the majority of people posting here don't anchor up wind of me
to use those lower scope multipliers i think a french flag is required to be flying on the stern

[svinvictus2]

My wife and I are live aboard sailors for between 6-9 months of the year every year for the past 15 years. We pride ourselves on the fact that once securely anchored we can always sleep well through the night.
I've never heard of these formulas for anchoring. One needs to carry the correctly sized anchor for your boat...our main anchor is one full size up. We are a 45' boat and our main anchor is a 60 lb. Manson Supreme. Next you need appropriate rode. We carry 3/8" BBB all chain gear which is proper for our windlass.
We follow the common rule of minimum of 3:1 taken from where you drop. When possible 6 or 7 to 1 is better. If there is a blow coming I like to drop up to 7:1 where possible. We carry a total of three well or over-sized anchors so when necessary we use a second.
As to using different scope for different depths.....I say no. Whether you anchor in 15 feet or 60 feet follow the rule of Minimum 3 to 1 and up to 7 to 1.
A rule that has kept us saqfe for years is: chain does nothing for you in the locker.

[a64pilot]

I've been able to avoid crowded anchorages for the most part. I just don't like people on top of me, plus if on a weekend some ass is playing loud music of some kind as often as not.
I leave and go elsewhere if the anchorage is crowded, so far. I know that will not always be an option. Last year I was behind Shell Island in Panama City, anchored out in the deep by myself when a strong squall blew through, it was interesting watching all the drunks boats get blown downwind, lots of drunks in the water, amazingly no one drowned.

[barnakiel]

Originally Posted by jkindredpdx

Is that when you use all your chain and just add rope to get a sufficient length for a comfortable ratio?

The chain we carry on the bower (100 ft) IS sufficient. The rope we carry is an optional extra (and used mostly along the lines I explain further on).

You are less likely to use more than 100 ft of chain in most West Indian anchorages - you are limited by other boats, not by how much chain you might have.

Unless you anchor in the last row, which is hardly ever done in a small boat like ours. And not because of the depths but much rather due to the rowing distance to the shore.

We have rope and chain rode because in our boat it is impossible to have hundreds of feet of chain only - our boat is only 26' and 3t of displacement. And I could not lift more than maybe 100 pounds of weight, hence the extra of the scope is rope for me.

If I were in a boat without such limitations, we would be all chain on the bower. But we are not, hence I said PRAGMATICS before calculations (much as the calculations may hold in the perfect world).

One nice thing about chain plus rope is that once the chain is out the extra rope becomes a snubber.

It is also very easy to manhandle the rope. Useful feature when you want to row the anchor off.

Cheers,
b.

[kas_1611]

Originally Posted by Rhwins

Don't forget to account for tide in areas with it. Here in SOCAL, its about 5' of difference between low and high tide.

Easiest way to remember that is MAX Water Depth expected plus bow roller height.

In parts of the UK tide ranges can be as much as 14m (35ft)

[barnakiel]

Originally Posted by Sailmonkey

Only for a hurricane.....IMHO, if you need a 2nd anchor to secure you in any kind of wind, you need a better primary anchor.

Yes.

Correct in the aspect of high winds.

Otherwise a good practice when not bothering your neighbours.

Makes for hours of careless trekking in the bush while the currents may be doing whatever they like with our boat.

I normally place the bower as is (this often implies closer inshore, shallower, and towards the wind). Then I place the second in the dinghy and let the wind blow me off to the lee. There I drop the second (easy as our second is only 22 ponds and maybe 10 ft of 8 mm chain). Very often this is deeper and further offshore.

Sure thing, this may be pointless in the end BUT man it does let you relax while away from the sight of the boat.

Cheers,
b.

[Mithril Bham]

Good stuff.
In the San Juans it's 3 to 1 since holding is good and anchorages are crowded. Wind increase let out more.
Annapolis recommends 7 to 1.
When I anchor in winter and it's blowing 40 I let it out almost all the way.

Always use a snubber.

[conachair]

Originally Posted by denverd0n

This ^^^^^.

Unless you are in a very crowded anchorage, what good is trying to get by with the very minimum scope? Put out 5:1 or more and sleep easy.

The calculations are simple. In 15' of water with about 4' of freeboard? Call it 20' altogether, times 5 equals 100' of rode. How hard is that?

Not hard at all.

Also not hard with the equation above to work out that with 2 x 6m + 23m or 35m, or a scope of nearly 6:1 it will take a quarter if a tonne force down the chain to lift the last link off the sea bed with 10mm chain.

[skipgundlach]

Originally Posted by nigel1

I'm in that school that thinks that chain in the locker is just wasted .

From the calculation provided, if anchoring in 50ft, then you deploy 150ft of chain, which to me is bare minimum and OK if you have a good high holding power anchor and in settled conditions. BTW, have you taken into account the freeboard, the height between waterline and bow roller.

If the wind is blowing anywhere above 25 kts, and you have a ratio of 3:1 or even 4:1, I would think that all of the chain will be off the sea bed, but the more chain you can put out, the less the angle the chain makes to the sea bed, and the less likely the anchor will break out.

Obviously proximity of other boats will have to be taken into account, but in the main, I try and anchor where I can at deploy 7:1.
I've been stuck in a bay with sustained winds of 40kts, gusting to 50, with a scope of 8:1 and felt pretty secure. At 4:1, I would have been crapping myself

Have you seen this thread
http://www.cruisersforum.com/forums/...ml#post2175924

What he said!!

I said approximately the same in the cited thread above; I - with a double oversized Rocna - nearly never lay less than 7 x (high tide plus bow rise).

But I sleep well at night. If it's going to blow, I'll go to 10x...

So, mostly, the first half of our 275' of chain gets in the water, as we're usually in under 10' depth. But even 15' with a 5' bow rise is only 140' or 200', if it's going to get gnarly...