Photos of Anchors Setting

[monte]

The kobra struggling with the Rock and coral substrate

[Bregts]

Pictures of my 25kg Delta copy in the soft sand of Bora Bora.
We are currently riding out some semi strong winds (30 to 35kt's) and it looks as if last night we reached the maximum holding power for my anchor in this type of sand. On the second picture it looks as if the anchor dragged a few meters. (chain marks in the sand)
It's set on a little sand bank in about 4 meters of water with 45 meters of 8mm chain and a 3 meter nylon snubber. Depth under the boat is 7 meter but the place where the anchor is dropped is more or less horizontal. There was some wave action as we are on a lee shore.

Any opinions on the dragging? Would adding my aluminium fortress anchor in tandem be a good idea the next time?
In the mud of Muros in Spain we had 50kt's for a night and a day without problems.

Boat is 34ft

[Viking Sailor]

Looking at the debris around the anchor I can't detect any sign of dragging.

[noelex 77]

Originally Posted by DefinitelyMe

1) Why do you think ships haven't come up with anything better than what is essentially just a lump of metal on the seabed?

Big ships anchor too deep for me to get a look at how their anchor is working. I do occasional see large power boat and even superyacht anchors. The stockless anchors don't seem to work very well, but I don't see many of them.

As I understand it, large ships rely much more on the holding power of the chain so easy handling storage is perhaps a more important parameter when choosing an anchor. Turning around a large anchor that has come up backwards for example would be very difficult with these very heavy anchors. So a symetrical design may be vital, which limits the design choices.

Originally Posted by DefinitelyMe

I have always subscribed to the 'bigger is better' philosophy but having spent many hours looking through your pictures i'm reconsidering that. I have a rocna 25 on my 36-foot boat and it is probably a size too big i'd say. I've never managed a complete bury from the force of the engine alone - the engine simply isn't powerful enough. Normally only the tip is buried. Because of this, when the breeze shifts around and the anchor rotates it does so relatively easily and often breaks free before re-setting.

A larger anchor has more reserves of holding power, but for any given force it needs to bury less deeply than a smaller anchor of the same design.

An anchor needs to be reasonably buried to rotate or shuffle well.

It has been suggested that for the above reasons that it may be possible when adopting the BIB (Big Is Better) philosophy to fit an anchor so oversized that the boat may not be able to generate enough force to set the anchor to the reasonable degree needed to allow the anchor to shuffle. Thus the anchor would have high holding power, but would only be set properly by strong wind.

My Mantus anchor is oversized, as was the Rocna I used before this, and I have not seen this happen in practice. The sets I have achieved often in a hard substrate are well above the minimum required for the anchor to normally "shuffle" or rotate without breaking out.

Your anchor is a little above +1 (one size larger) than recommended in the sizing tables. This sort of size is often used on long distance cruising boats and should not cause any problems. The Rocna is an excellent anchor for both setting and rotating well so I am not sure why you are experiencing it breaking free during wind shifts.

The substrate does have to be reasonable for the anchor to "shuffle". For example, if there is only a thin layer of sand over smooth rock, the anchor will not achieve sufficient penetration to "shuffle". With a wind shift the anchor will typically break out and drag until it has piled up enough sand in front of its fluke to hold again. The ultimate grip and reliability is of course very low but there are limits to what even the best anchors can do.

Action cameras are readily available these days and not very expensive. Could you borrow one and post some photos? It would hep analyse what is going on.

[noelex 77]

This was a Bruce.

It was dropped in medium/thick weed. It had dragged to a clear patch of sand between the weed beds and had then set quite quickly.

It is sitting nice and upright and while not all the fluke is buried, it looks like it is setting well.

[noelex 77]

This was a Delta not doing very well in my opinion. 4m @ 5:1.

It had moved backwards about 5m at this point and was still very poorly set with just the toe in the substrate.

The shank might have actually been buried better than the fluke!

[monte]

Wind has set the Kobra a bit more, but really this loose coral and Rock is one of the worse substrates it's seen.

[noelex 77]

This was a Claw (a Bruce copy).

This boat anchored in thick weed and the anchor did not hold. They re-anchored and almost collided with another boat. Then a very messy third drop produced this result.

You can see the anchor has set incredibly quickly in about the same distance that is seen with the very best anchors. There is some heaping up but the fluke is nicely buried under the substrate, not just covered by the heaped up sand. The shank is still exposed but the Claw/Bruce is a "tall" anchor. The fluke has to buried a long way down before the shank starts to bury.

The anchor is nice and level.

The Bruce/Claw does on occasion produce some very good results. Even when well buried, the unique shape of the fluke does not seem to produce as much holding power as the better anchors though. It needs to be oversized to make up for this difference.

It does very poorly in traditional anchor tests, but it is a very hard anchor to classify well.

[noelex 77]

This is a Kobra.

At this stage it has not been given much force. I would expect it to do better with a longer setting distance.

The Kobra usually sets a little quicker than the Delta and you can see that this one has started to set after moving about 4 feet, but the better anchors would be completely set in this distance.

[noelex 77]

This was a "mooring" rather than a boat's anchor.

A lot of these are set up by the local fisherman so they have a spot to sleep for the night. They often use anchors rather than the normal heavy weights we associate with moorings.

These moorings are not very good at revealing anchor performance because the sand marks get smoothed over after a period of time so it is very difficult to know the history, or if the anchor has moved. This anchor could have been just dropped in this position with very little force subsequently applied, although that is unlikely.

This was a Danforth (or more accurately a Danforth copy).

You can see it has such a high list it is almost at 90°. The flukes had very little grip. Unfortunately Danforth style anchors do sometimes adopt the this attitude in hard substrates. In some circumstances they can drag for large distances seemingly stable in this orientation. The Guardian in post #1713 and post #1732 showed some of this behaviour so you can see it is a problem not just confined to crudely made Danforth style anchors like this one.

BTW note the seabed behind the anchor. Many people falsely imagine the seabed is always flat.

[noelex 77]

It is always interesting to see an anchor responding to wind force alone. Watching how the anchor reacts to just the pressure of the wind on the boat removes operator error out of the equation.

The anchor should set by itself in a reasonable substrate with an adequate scope.

This Delta was not doing a good job.

It had been set under engine force and had a long drag mark. The wind then switched almost 180° and the Delta started to drag back almost in the direction it had come from (later photos will make this clearer).

Given long enough, I think it would have made it back to the drop point . If your anchor cannot hold, at least arrange the wind so that the anchor drags back and forth and never really goes far .

We arrived just as the anchor had rotated around. Over the next 45 minutes we watched it drag back a few inches with each gust. These slow drags are far more common than people realise.

I will show the progression in the next few posts.

The rock is a good reference point. At this stage we had already seen the anchor slide back, but were a bit too slow getting the camera ready.

This is the start after the anchor reversed direction. It was dragging at this stage. You can see the clouds of sand that are given off as the anchor moves:

[noelex 77]

It then paused:

[noelex 77]

Here it has moved back a bit more. More puffs of sand. A lot of the bury is heaping up of sand, but it is at least starting to rotate upright. The Delta does rotate upright quite early, not long after it has started to dig in:

[noelex 77]

It has moved back a bit more here. Unfortunately, here it lost a bit of grip and fell back on its side. In this distance the better anchors would have set completely, but the Delta looks no better than when it started.

[arsenelupiga]

thanks to your pics, i replaced 20kg delta with 25 kg rocna.

Had 2 interesting nights with delta. Luckily no serious damage.

See if this "new generation anchors" are of any value.

However, I also upgraded chain grabber to protect my anchor winch, i hope even in storm conditions. So far, pulling anchor up in 30 kn wind I managed zero force on anchor winch except for weight of anchor gear itself.

Sudden pulls were handled by chain grabber on dyneema rope.