Photos of Anchors Setting

[kas_1611]

Agreed Noelex that is a well set Delta. I've seen mine in a similar state although I will admit not quite that well dug in, normally can still see the top of the shank.

The mind boggles as to why the need for 40m of chain, that's just OTT in my opinion. Cats can go shallower than us monohulls as they don't have quite the draught but still 2m is very shallow. The wind only has to swing on you, even by 90º and you could find yourself touching the bottom, or even drop to dead calm and you drift with any current until....bump.... you have bottomed out. Should be a golden rule of anchoring - anchor as if you expect the wind to shift 180º because you know that one time you don't it will.

Keiron

[noelex 77]

There is an argument for more scope at shallower depths, but this was way over the top. You need to allow for the roller height when calculating scope so I estimated more like 70- 75m of chain (72 / (2.2 + 1.4) =20:1. 2.2m the depth of water and 1.4 bow roller height) Of course this is a rough estimate and subject to some error, but really all that counts is that it was lots.

The wind at this time of year is generally nearly always from the N or NW. This year has been a bit unusual with some southerly winds and there are always atypical local effects, but with a 20-25k forecast from the N, gambling on no southerly is reasonably safe. However I agree with you in that you should be wary if you elect to go with a scope that does not allow a 360 swing.

Having said that at my current 5:1 I would hit a rather nasty rock if the wind swung around to south and was enough to straighten out the chain. If the wind lightens off I will go back to my initial 2:7:1 scope which provides a 360 degree swing circle. (Actually having snorkelled the anchorage 3:1 or bit over would still be OK so I will probably use this)

The Mantus is managing very well at short scopes and I feel confident using at 3:1 or less in reasonable conditions and moderate depths. It is oversized which also helps confidence at short scopes.

[kas_1611]

I've always calculated scope by the following:

(Water Depth x4) + Bow Roller Height + Expected Tide

so in 2.2m of water (not that I can anchor in that shallow I hasten to add ;-) ) I would have 4x2.2=8.8+1.5+1 giving a total of 11.3m of chain. As winds were expected to be around 20kts+ I'd drop another 2m to go to 5x depth then snub it off, which adds about 1m for 14.3m out, assuming it is safe of course. Average tidal range in the Adriatic is normally less than 1m.

Problems come in anchorages when you don't know what people have put down, only takes one muppet to let down 20x water depth to create havoc when the winds shift. Something we have noticed in the Adriatic is there are a lot of people who hardly drop anything and some who appear to drop everything, either dumping it on top of their anchor or in high speed reverse (these guys have normally dropped the hook while still motoring forward at great knots!!).

Keiron

[monte]

Should really be (depth + bow roller height + tide) x 4
If you calculate 4:1 using your method in 2 m depth you will have 9m of chain out which is actually 3:1 at low tide and close to 2:1 at high tide.
Ie 4:1 should be 16m of chain out.

[noelex 77]

Originally Posted by kas_1611

I've always calculated scope by the following:

(Water Depth x4) + Bow Roller Height + Expected Tide

so in 2.2m of water (not that I can anchor in that shallow I hasten to add ;-) ) I would have 4x2.2=8.8+1.5+1 giving a total of 11.3m of chain. As winds were expected to be around 20kts+ I'd drop another 2m to go to 5x depth then snub it off, which adds about 1m for 14.3m out, assuming it is safe of course. Average tidal range in the Adriatic is normally less than 1m.

Problems come in anchorages when you don't know what people have put down, only takes one muppet to let down 20x water depth to create havoc when the winds shift. Something we have noticed in the Adriatic is there are a lot of people who hardly drop anything and some who appear to drop everything, either dumping it on top of their anchor or in high speed reverse (these guys have normally dropped the hook while still motoring forward at great knots!!).

Keiron

What is important is angle of the rode at the shank. If you think about the maths the correct formula for scope is:
Rode length / (depth of water + height that the snubber or rode is above the water)

The depth of water should be where the anchor is dropped (not the depth where the boats ends up) and needs to be adjusted for the tide (most people use the worst case at high tide, but you can calculate the scope you actually have at any point in tide if you want).

This formula gives you the correct mathematical scope. Of course you can use any formula you like to determine how much rode to put out, but it is not correct to refer to the multiplication factor as scope unless it is calculated correctly.

An example might be 10m +3x the depth of water at high tide (or 5x if you prefer), but there are as many formula as there are sailors. The better ones make some allowance for a greater scope in shallow depths by introducing a constant, like the above.

[kas_1611]

Originally Posted by monte

Should really be (depth + bow roller height + tide) x 4
If you calculate 4:1 using your method in 2 m depth you will have 9m of chain out which is actually 3:1 at low tide and close to 2:1 at high tide.
Ie 4:1 should be 16m of chain out.

Monte,
I can see your reasoning although your maths is wrong, using my calculation in 2m I have 10.5m of chain out. It also means you need a shed load of chain/rode if you are anchoring around the British Isles where tidal ranges are up to 14.5m!
Given the minimal tidal range where I am it is not that critical but I will adjust my calculation table to include my bow roller height from now on.

Noelex,
I was never any good at maths at school, which is why I became a Geologist (+/- a million years is good enough for us), but you are correct when you look at it in terms of triangles. The bow roller is the 3rd point of the triangle with the anchor the second point and the right angle below your bow makes the triangle. Time to dig out my Pythagorus and a pencil me thinks

Cheers for the maths lesson guys

Keiron

[noelex 77]

What is more expensive than an Ultra anchor?

Well two of course . This boat probably has $15,000 dollars worth of anchors on its bow.
Let's hope they haven't moused their shackles .



The boat concerned is a large power boat (75-80feet?). They dropped the single Ultra a long way out and backed up to shore, tying their stern to the rock (Med moor) that I mentioned earlier was in my swing circle. They had about 130m of chain out , but the anchorages here get deep very quickly so the anchor was in about 25-30m of water hence the poor photo.

They did not put any winching force on the Ultra so it is just sitting on the bottom. This is no fault of the anchor. It has not had any force to set it. The wind is very light and the long length of thick chain is probably enough to hold the boat without much contribution from the anchor.

[NornaBiron]

At last, we have our new windlass and new 100m of 12mm chain fitted onto our 45kg Spade. Attached are 3 photos: 1 of our Spade set with a 5:1 scope as we were med-moored to the shore, the 2nd is of a well set delta in the same spot (not sure of the scope) and the last is of a good old fisherman's dropped from a Turkish gullet beside us with around a 10:1 scope. They do like a lot of chain in Turkey!

[dugout]

Noelex 77:

What camera is your wife using? Sorry if you already mentioned it but I cant find it. Thanks!

[noelex 77]

The camera has been great.

It is an olympus TGi-2. The camera is waterproof to 18m on its own, but I use an underwater housing as well. This is called PT-053.

The underwater housing basically doubles the cost of the package, but as it used several times a day I felt the the housing was good insurance.

Olympus has recently released the TGi-3 which is an updated version. One nice feature the 3 has is time lapse. It would be great to to put the camera on a tripod next to the anchor and get a time lapse of the anchor rotating, or setting deeper with strong wind.

[dugout]

Thanks, given your obvious routine use, this says a lot about the durability of your chosen camera kit.
Your study is very helpful, this is a great topic. Thank you for the time and energy devoted to it. Very constructive.

[noelex 77]

A light crosswind developed. This can create a reasonable force on an anchor when Med moored. The boat concerned wound in some anchor chain. This is a common way to try and set the anchor when Med moored, although it is better to do this conventionally with engine force or momentum if possible. This is often difficult to do when trying to tie the stern up at the same time so the winch is often used. With the stern tied, the force is applied to the chain and anchor. The winch provides a smooth and progressive force. This is ideal for starting the setting process. The force generated is not high even with a hydraulic windlass, so the set will tend to be shallow.

Disappointingly, they wound in a considerable amount of chain (25m) before the angle indicated that the Ultra was starting to grab. 130m of chain chain does develop a fair bit of slack, but the amount of chain retrieved indicated the anchor was taking some distance to set.

I went for a dive and this was the result:
The Ultra has started to dig in. It looks ready to dive down and set properly although at this stage it has only its toe buried. Unfortunately, the water was too deep and the photographs too indistinct to confirm how long the anchor had taken to set.

Note the anchor had two extra tabs welded on the shank halfway along. A large area of the top of the shank had been roughened up. The latter could have been abrasion with some part of the bow roller but it looked like it had been done by a sanding disc. I wonder if the shank was bent and split along the top at some stage and the weld area had been ground back with the tabs acting as reinforcement. It is also possible that the tabs were welded to support the anchor on the bow roller and stop it bashing back and forth. This treatment had only been done to one of their two anchors.

Ultra anchors are covered by a lifetime warranty. If the shank was bent there is no need to try and repair it. Ultra will replace it. There has been a change of shank design with some internal bracing added to shank in the later models.

[noelex 77]

Another large boat Med moored with a 180kg stainless steel stockless anchor. I spoke to the skipper who was very proud of his anchor and told me he had 150m of chain out.

Beware of Med moored boats they can sometimes use a lot of chain and it is easy to lay your chain over the top of theirs or vice versa. Most yacht winches cannot raise a 180kg anchor and 150m of 16mm chain .

Anyway, this was the result (in about 20m of water). The anchor had never had any force applied to it and was consequently unset.

[noelex 77]

In the meantime the Mantus is beautifully set and has dug in slightly deeper with the wind last night which was 30 knots for a couple of hours.

10m is a much nicer depth to photograph anchors

[CaptTom]

Nolex, thanks for all the research!

Now, a really dumb question I'm sure, but be kind to me; I boat in the Northeast US where the visibility underwater is rarely over two meters. And way too cold to dive into without a wet suit. So my anchoring is almost always done on pure faith.

What's the point of the short line with the float on the roll bar?