Photos of Anchors Setting

[kas_1611]

Great series of photos Noelex. Very valuable insight to how an anchor behaves in the real world and I am sure an eyeopener to many.

Keiron

[arsenelupiga]

Originally Posted by kas_1611

Great series of photos Noelex. Very valuable insight to how an anchor behaves in the real world and I am sure an eyeopener to many.

Keiron

looked at your pics...

Plastic Waste - Plastic waste seen in a small embayment off a nice anchorage in Croatia Cruisers & Sailing Photo Gallery

this is yuk! Is this somewhere in asia/india ?

i see where it is now from your description.

[noelex 77]

This is how it looked when we left it:

[noelex 77]

This is from near the surface where you can see the total drag marks including the long initial drag mark that occurred as the anchor was set under engine power before we snorkelled over.

Notice the rock was pushed back by the anchor. You can see the mark in the sand if you look closely. I wonder if the drag from the rock caused them to believe the anchor was holding?

Anyway, the skipper would not have realised anything was amiss, but this was not a good performance. The anchor has dragged 5m or so. When the wind turned around it broke out again and dragged a metre back in the direction that it had come from. After all this distance it still not set, or at least very poorly set.

The photos all show the anchor responding to wind pressure. So anchoring technique is not a factor.

[noelex 77]

This was a Brittany anchor.

It was a stern rather than a primary anchor. In this case the stern anchor was employed to keep the bow pointed into the swell.

This is a great, and under-utilised technique. Make sure you take into account though that you will swing differently from your neighbours.

In this case the anchor does not need high holding power. In fact if the wind shifts and picks up, in this application, a stern anchor that drags is better as it prevents the boat adopting a beam on aspect to the wind which can put a lot of force on the primary anchor. So a low holding power creates a "fuse" of sorts.


A Brittany anchor is not a bad stern anchor for this sort of application. It has a lot of the properties of the Danforth, but the absence of a stock means the anchor is easy to store.

This anchor was set on a very short scope with just a rope rode. This is fine in this application, but the anchor had dragged and caught a mooring chain. This was providing all the holding power. At times the Brittany was lifting off the seabed !

We offered to free the anchor for the skipper, but it was only in shallow water and he indicated that he would do so himself.

[noelex 77]

Later the skipper did re drop the Brittany. Still at a very short scope just on rope. Remember this is just a stern anchor to keep the bow pointed into the swell.

The Brittany was obviously severely struggling with a long drag mark, lots of heaping up and a high list. I did not watch it for long, but I suspect it was slowly dragging.

The anchor was dropped in shallow water close to the beach where the sand is nice and soft. Ideal for almost any design of anchor to set well. However, considering the scope (that you can see for yourself) what a gutsy performance by this anchor.

The maximimium holding ability will always be with the rode pulled as parallel to the seabed as possible. However, anchors can hang on, bury and provide some grip even when the rode is pulled up, as this very extreme example shows.

[noelex 77]

This was the same anchor as the "octopus" Delta shown in post#1794.

The anchor is essentially unchanged (possibly buried just a smidgin more?). I posted this to show that in anchors with any weed nearby, broken strands tend to accumulate in the depressions over time. From the surface this can give the anchor quite a different appearance.

Also be aware that the sand tends to gradually collapse filling in the gaps behind the fluke. Unfortunately any heaped up substrate in front of the fluke also tends to gradually fall away. If the anchor relies on heaping up the sand in front of the fluke for much of its grip, this means a gradual drop in holding power when this sand levels out.

Anchors that dive the fluke below the substrate with minimal heaping up are not effected in the same way. With time the substrate regains some of its shear strength so the holding power will if anything improve.

The sand here tends to be very stable. It takes a long time for drag marks to disappear, for example, but in softer sand like I see in Australia this collapse and filling in of sand occur much more rapidly.

This is a reminder of how the anchor looked:




This was later:

[noelex 77]

These are grapnel type anchors. The smaller models are sometimes made from re-bar. These were reasonably large and I think made from pipe and solid rod. They are sold cheaply in chandleries here in a multitude of sizes and used a lot by professional fishermen.

They at least dig through weed well and also stand a better chance of gripping in rock. The fluke area is very small particularly in this design, which seems popular. Only two of the flukes have a plate welded on. The other two are just round rod. On the other hand they use large anchors considering the small size of their vessels.

The local fishing boats are only small (most are a one man operation), and have a very low freeboard so they don't venture out in any sort of weather.

Notice the weed bed towering away in the background. These sort of local elevations can reduce the effective scope:







This is another one that looked like it had been in place for a while:

[noelex 77]

This was a Delta.

It had been dragged a long way and was still only very tenuously set:




From above the anchor does not look too bad, especially from the surface where the elevation associated with the heaping up cannot be seen. If you don't want to dive down try to at least view the anchor from the rear. As you can see looking at the first photo from above and in front it is difficult to know what is really happening.






The following photos from in front and behind show the set much better. Notice how the fluke has barely penetrated below the layer of the substrate surrounding the anchor. The front of the fluke is reasonably covered in sand, but this is not the fluke diving down below the substrate, but rather the fluke pushing a big pile of sand in front of itself.

Sets like this look OK from the surface, but the heaped up sand is very soft. It has very poor shear properties and minimal grip. An anchor that can dig under the substrate will have much more grip even if the fluke area covered is similar.

In addition, if the wind changes and the anchor rotates an anchor that does not bury the fluke under the substrate no longer has this mound of sand in front of the fluke. If the fluke is barely below the surface of the substrate, as is the case with this anchor, there is very little to hold the boat.

Anchors pile up sand in front of themselves like this when the fluke is struggling to penetrate. If you look back on the photos you can see which anchors often simply heap up sand and those that do a much better job and dig the fluke down into the substrate. You will also find there is strong correlation between anchors that heap up the substrate and those that take a long distance to set. Anchors that hold primarily by heaping up the substrate need to travel a long distance before enough sand is accumulated in front of the fluke.

These photos in front and behind from close to the seabed show the heaping up of the substrate and how little of the fluke has actually penetrated below the level of the sea floor.

[noelex 77]

This was a small CQR. It was dropped close to the beach in softish sand in 5m @ 6:1.

There was a very shallow drag mark extending a long way ( it can be seen extending to the top right of the last photo). From the scrape marks in sand it can be seen the wind has rotated around 90°. The CQR has not dragged backwards only rotated. However, it is still not well set with only one side of the fluke buried and a list of 90°.

From this attitude to set properly it will need to rotate upright. The CQR has a very heavy shank and is slow to do this. In hard substrates it often remains on its side like it is here.

The sand marks don't show any sign of a deeper set so I suspect it was it always on its side and just scraped its way around rather than fell over as it turned.

[Kenomac]

For the first season on our present boat when we successfully used a Lewmar 75 pound CQR, we utilized a completely different setting technique than the anchors shown, and from the way we do things today using our Ultra anchor.

I would always let the CQR freefall by releasing the windlass maually and allowing it to crash into the bottom as the boat was drifting back with the wind, or idling in reverse. It always seemed to bite quite well this way. But when we let it down gently using the windlass motor... no bite.

Ken

[monte]

Here's a few dodgy pics from this afternoons snorkel. Horrible seabed here but good for checking anchor performance I guess. There was a rocna I didn't photograph that was also just tip in. Here's a spade (I think) followed by a couple of cqr's that are just laying in their side scraping the surface, and a delta. Hopefully the cqr's won't be upwind if the wind backs..
Lastly a pic of our kobra. The delta and cqr's looked about 20 kg, the spade around 35kg and ours is 25kg.

[noelex 77]

A Delta.

These numerous Delta anchors are so similar in performance that they start to blur into one another.

Another long drag mark, this one filled with tiny broken strands of weed, almost like dust. These tend to swirl around the bottom and collect in low points.

[noelex 77]

This is a FOB HP anchor.

It is a Brittany variation. They are popular on French yachts. The anchors are well made. They even produce a model in aluminium and titanium with an adjustable fluke angle!

This model had been dropped with little force placed on the anchor so it tells us little about the performance.

The shank was slightly bent:

[noelex 77]

This was an atypically good result by a CQR (genuine I think).

It was dropped by a large yacht (70 feet?) in very deep water on a long scope. The puffs of sand are indicate an anchor that has moved recently. In this case the anchor was not dragging. The puffs of sand were as a result of the setting. The photo was taken just after the drop.

It is one of the best results I have photographed from a CQR in a long time. The anchor has rotated upright and 3/4 of the fluke is buried. There is still a fair bit of heaping up and the anchor took a long distance to set, but still a good solid and reliable set.

If you can find a patch of medium soft substrate the CQR, or any of the plow anchors will set very well generally. Owners that use these anchors in these so called "Goldilocks" substrates (not too hard & not too soft) cannot understand why everyone does not love this anchor.