Photos of Anchors Setting

[Jim Cate]

Kinda looks like the anchor was assembled incorrectly... maybe! I wonder if the transverse bar on which the flukes are welded went through the lower hole if the fluke angle would have not been correct(er).?

But that does get my prize for being the worst Danforth type ever seen on earth!

Jim

[Don C L]

Originally Posted by noelex 77

This was a Danforth anchor. I usually say at this point it is more correctly called a Danforth copy, but perhaps this particular anchor could be more correctly called a Danforth copy made by a blind man with no concept of geometry . 8m@6:1.

It belonged to a small (about 30 feet) power boat. They dropped a long way in front of us, but were obviously slowly dragging towards us. When they reached within shouting distance I let them know their anchor was not holding. It should have been easy to pick up the anchor, but they could not raise it.

Our conclusion is that they had snagged our anchor. It is worthwhile thinking about the strategies you will employ if this happens. It should be easy to sort out, but it can be a real mess if you are not careful.

To cut a long story short we snorkelled over their anchor expecting to have to release their anchor from our chain, but it was not caught. It turns out they could not get the anchor up because their windless clutch was slipping and they did not have a winch handle . It would be nice if all problems were so easily solved, so I swam back and lent them a winch handle.

I think this anchor gets my vote as the worst Danforth anchor so far. The fluke angle was about 80°. The shank was too short. But it was shiny .

It had a second hole in the crown and it looked like the fluke angle should have been adjustable like the Fortress and FOB anchors, but I could not see how this could be done. Perhaps it was designed to be welded in one of two positions when it was produced.

After a drag of perhaps 500m the anchor managed somehow to get some grip and held the boat in 20 knots with gusts to 25 knots. Even a very poorly performing anchor can hold in these sort of windspeeds.

Oh, by the way, we traced the drag mark and it missed our anchor chain by about 5m.

This was the anchor when we first arrived. It had dragged several hundred meters at this stage and was moving back in each of the gusts. You can see the puffs of sand given off by the moving anchor:






We came back a couple of hours later after seeing some of the other anchors. The anchor looks terrible, but it had piled up some sand and had enough grip to hold the boat in position in 20 knots. This shows how the anchor can be doing a very poor job, but still hold the boat successfully. Fish love shiny anchors:

yikes.
and is that stainless or aluminum?
I can just hear them... "those darn Danforths never work!"

[jongleur]

Unbelievable! Surely someone must
tell the owner that this anchor is
incapable of doing a proper job in
any circumstance.

[noelex 77]

This was a claw (a Bruce copy).

It was dropped by a big, high performance powerboat (50' ?), but it was a very small anchor for the boat size.

They stern tied to the rocks with their back into the wind, so their anchor fortunately did not need to have much holding power. The substrate once again is smooth rock, but this time with a very fine layer of muddy sand on the top.

Smooth rock with a fine sand layer on top is one of the more common of the challenging bottom types and with deeper sand some anchor designs can get a moderate grip, but this sand was too thin for any anchor to hold.

There was a big (3m X 3m ?) abandoned mooring just near the anchor. It still had the riser float intact, but was missing anything going to the surface. Pity, as it would be more reliable than anchoring on rock.

[noelex 77]

The wind picked up to perhaps 25 knots. This is a good time to look at anchors, as the wind provides a nice setting force and providing the scope is adequate and the substrate reasonable, good anchors should set well.

This was a large Delta dropped by a 50 foot cat in 3m @ 6:1. This was a reasonable distance from our anchor, but it looked liked good sand. The performance is a bit dismal if this is the case.

There was a long setting mark and most of the bury is just a large amount of heaped sand rather than the fluke diving down. It was a big mound of sand.

Contrast these pictures with instant dive of the Mantus. Perhaps there is some rock inhibiting the diving of the Delta?

[noelex 77]

This anchorage has both good soft sand and smooth rock.

Often (but not always) with these sort of anchorages there is rock under the sand. If the sand is deep enough the anchors performs normally. If the sand layer is very thin the substrate is much like smooth rock where anchor design does not mean much. The anchor can only cling to small depressions in the rock, as we have seen in the photos.

Between these extremes is where it gets interesting. Here anchor design is important and some models can get enough grip to hold, at least in moderate wind, even if sand layer is reasonably thin. Others fail dismally.

The Ultra was in such a substrate so its performance is interesting. At first glance it does not seem to be doing a great job considering this is an expensive anchor. The setting mark was over 5m long and the fluke was not well buried. Much of the bury was sand heaping up. 6m of water at 3.5:1.

However, this was a very thin sand layer and the anchor was doing a good job holding the boat in 25 knot winds, although perhaps it hooked onto some rock below. I will try and go back to examine the hole left by the anchor when the boat leaves. If the anchor is not hooking onto rock the performance is very good considering the difficult substrate.










Ultra make beautifully finished anchors:

[Opie91]

Originally Posted by noelex/

I think this anchor gets my vote as the worst Danforth anchor so far. The fluke angle was about 80°. The shank was too short. But it was shiny

Set she may, shine she must.

[noelex 77]

There is a lot of debate about the benefits or lack thereof of chain weight and catenary. My view is that the weight of the chain is of some help in setting the anchor, but the benefits of chain weight disappear in strong wind. In the early, critical stages of the anchor setting when the force is just starting to be applied and the anchor is starting to dig in, the catenary keeps the chain angle low and the pull close to parallel with the seabed. So if you have an anchor that is struggling to set, then chain weight helps. It also helps the holding in light/moderate winds, but the benefits are minimal in strong wind.

The wind force here was just at the stage where the catenary was starting to disappear in the gusts. This was about 25 knots of reasonably steady wind with perhaps 30 knots in the gusts. This was in 6m of water at 3.5 : 1.

In this wind strength the chain was still on the seabed during the lulls but nearly all the catenary was lost in the gusts as the photos show. This catenary in the lulls is still of some use. It helps to reduce the snatch loads on the anchor, although a nylon snubber can also be used in this role. The snubber will continue to offer some elasticity long after the catenary is gone.

Despite these slight elasticity benefits, at this stage the main advantage of catenary, which is to reduce the upward pull on the anchor, has been largely lost. If the anchor is going to drag it will do so in the gusts and as you can see, the chain is very close to being a straight line when the gusts hit.

This is only moderate wind. More chain, or heavier chain, could restore the catenary, but the force on the anchor goes up roughly as the square of the windspeed so even a lot of extra weight only increases the windspeed where the catenary is lost by a modest amount.

It is worth remembering that more scope, even if it is rope, will reduce the upward angle of pull you can see on this anchor.

[noelex 77]

This Delta was dropped very close to our Mantus. 8m@5:1

The Delta can do well in soft substrates. The setting distance becomes much shorter and the anchor can bury much more. This substrate was soft enough that the Delta's setting distance while still longer than the best anchors, is reasonable.

Unfortunately, the anchor has still not managed to dive under the substrate, but rather has mostly just piled up a big, and I mean big, mound of sand.

Note this anchor shank is slightly bent which may have effected the results, but it has behaved almost the same as the Delta in post #2330











The drag mark in the bottom of this photo is left over from the Danforth in post #2325:

[noelex 77]

This Rocna was dropped by a 34' charter yacht that stayed the night.

I see a lot of anchors underwater. The boat was holding in 25 knots, but somehow this Rocna did not look right. I could not quite put my finger on what bothered me .

Any suggestions?

[sanibel sailor]

neutral buoyancy? Float snagged on something?

[SailRedemption]

Well it appears the shackle on the anchor to the swivel is on the small side.

Did it dislodge right when you were taking pictures?

See more @ redemptiverepair.com

[malbert73]

Tandem anchors? Would show pitfall of that flawed technique.


Sent from my iPad using Cruisers Sailing Forum

[noelex 77]

You guys are too smart

Here are some more shots of the incredible "Floating Rocna".










I will post some photos of the whole arrangement shortly.

[noelex 77]

These pictures shows better what is happening. The skipper deployed a tandem anchor arrangement. They have not used the correct hole in the Rocna to attach the the second anchor (it should be the lower hole in the shank just above the fluke) but I doubt it would have made much difference in this case.

When tandem anchoring, it is tough to get both anchors to set. It helps to use the same design of anchor, or at least one with a similar setting distance, but the risk is just one anchor will bury. If the end anchor sets, as in this case, the anchor closer to boat will might not even be on the seabed most of the time, as illustrated here. Even when it touches down it is not in any position to dig in. Even a heavy unset anchor will be off the bottom continuously in strong wind in this situation.

The Rocna is therefore just acting as a dead weight or kellet (sometimes called an Angel or Chum). Most experts agree a kellet does little to improve the rode angle and here is the proof. This was only 25 knots but the Kellet (the Rocna) was lifting well off the bottom in the gusts. If you look at the rode angle the weight of the Rocna is helping very little during the gusts. Any slight benefit will disappear when the wind strengthens.

The other lesson here is how such a tiny amount of fluke that the Brittany has buried in the rock can hold the whole boat. It looked very precarious, but did not move the whole time we watched and they had already been anchored for a couple of hours.

It was a charter boat and I think the skipper had just attached the stern anchor to the primary, using the wrong hole and with a very dubious snap shackle. We sometimes see these sort of weird tactics by charter boats. A common one is to deploy a second anchor in a crowded anchorage when everyone else is just using one. The different swing pattern creates mayhem, usually at 2 am .

In this case, the second anchor was hindering the performance of the Rocna, although in the rock where they dropped no anchor can work correctly.

We had a word to skipper, pointed out where the sand substrate lay and suggested they ditch the Brittany. They did not speak much English, but they did reanchor a bit later. They still used both anchors. It is hard for some people to imagine one anchor could be better than two.

They held overnight.