Photos of Anchors Setting

[noelex 77]

Stunning photo

Originally Posted by hoppy

This rocks much more than photographing dumb anchors

Now go and wash your mouth out with soap

[hoppy]

Originally Posted by Kenomac

Hoppy,

Did you end up trying to set your anchor following the photo shoot? Looks like it's just sitting atop a large flat rock, as ours must have been last season, just before we dragged anchor and ended up on the beach. That sort of bottom can fool you, you power back thinking everything is fine....

See thread "Anchors are a drag, Waking up on the Beach."

Ken

So the wreck is your old boat, rusted away pretty quickly 😉

It's a morning after shot but looks exactly the same as it was last night. The tip had dug in to a gap in the rock or something and was holding me when I reversed up hard after going for a swim last night.

After the swim and looking at the proximity of land I actually shortened the scope from 6:1 to 4:1 so that I kept my distance if I didn't drag.

I knew the forecast was for a quiet night so I felt comfortable, but I did halve my normal GPS anchor watch from 200 to 100 feet and had the depth alarm set as well.


Sent from my iPhone using Cruisers Sailing Forum

[noelex 77]

This is generally called an Admiralty Stockless anchor, but there are a number of variations. I think this is a Hall or Union.

This was dropped by a large tourist boat. This yacht only stayed for an hour or so to give people a chance swim at a deserted beach. Consequently, they anchored at a very short scope. This was about 2:1 or maybe a bit less. You can see the chain lifting in only 10 knots or so of wind.

The Admiralty Stockless has a very small fluke area relative to its weight. It manages these short scopes very well. I doubt most modern anchors would do as well with the same scope. However, with the thick profile these anchors never penetrate deep into the substrate. With their small flukes the holding power is very limited even when the scope is increased.

If you panic at the thought of the chain lifting off the seabed have a look at the angle of the chain on this anchor . Note the chain angle is always much higher than the shank angle. Many people think the shank is pulled up at the same angle as the chain and therefore cannot imagine how an anchor can hold when the chain lifts significantly above the seabed.

In reality, as the anchor buries it forces down the shank despite the upwards force of the chain. The holding will always be better at longer scopes, but what happens underwater is not what many people envisage.

[hoppy]

Originally Posted by hoppy

I was not going to take a photo of my anchor today, but something I saw during a swim made me rush back and get the dive camera and mount the 10-18 lens on it. I'm much closer to the Rocna than it looks

Attachment 106510

This rocks much more than photographing dumb anchors
Attachment 106511

Rod Heikell totally misses this in his books. Who cares about a deserted monastery in the next bay

I've now posted more photos from this morning

Just so I don't upset the OP with photos of an UW subject that is far mor interesting than anchors, I've posted it in the DSLR thread
http://www.cruisersforum.com/forums/...ml#post1881992

[kas_1611]

Oh I don't mind the occasional interesting underwater photo that isn't an anchor creeping in here and there. Especially if it has a tenuous link to anchoring like your wreck Hoppy.

Sometimes it's nice to see some of the other stuff our anchors get to see

Keiron

[Kenomac]

Has there been an pictures of the Kobra anchor, anchored in the Mediterranean grassy, weedy bottoms? How do they manage in this sort of bottom?

The reason I'm asking, is my anchorage neighbor just purchased his Nordic Tug 38ft which came with a Kobra, and he's a little dismayed/concerned that it hasn't dug in after four days and nights. I looked at his anchor, and it appears as though only the tip has dug into the hard sand bottom. I'll post a picture later today. When I checked it four days ago, there was a ten foot furrow, then the tip dug in a few inches leaving the anchor on its side.

He will be encountering mostly hard sand bottoms around here covered with grass, and wants an anchor that will let him sleep well when the wind blows 35 plus unexpectedly.

Will the Kobra do a good job?

[noelex 77]

Originally Posted by Kenomac

Will the Kobra do a good job?

The Kobra is a convex plow anchor. It is very similar to a Delta, but has a longer skinnier blade.

Underwater it behaves in a very similar manner to the Delta, but the longer thinner blade and lighter fluke help its performance. It can penetrate harder substrates and weed better than the Delta.

The biggest drawback in weed is the requirement for a longer setting distance that is common for the convex plow anchors in hard to penetrate substrates. The broken and pulled up pieces of weed tend to accumulate as the anchor travels through the weed when it is starting to set. These get squashed under the anchor and make it difficult for the tip to get through to the underlying substrate. The fluke shape is thinner and sharper than the Delta, which is a big help, but the steel ballast in the fluke still creates a reasonably thick profile section that needs to be forced past the weed roots.

However, the Kobra is great value for money and is a good anchor overall. Thick weed is a difficult substrate. It is one of the very rare substrates that can trip up the modern new generation anchors that are otherwise so versatile. So often an anchor will hold the boat just by gripping the weed itself. This will fail in strong wind.

Unfortunately, in thick weed the only way of telling how the anchor has set is by feel, so it is hard to take photos that show the difference between good and bad anchors in this substrate.

There is a very strong correlation between an anchor's performance in hard sand and in weed. An anchor's ability to perpetrate hard sand generally translates to the ability to do the same in weed. Conversely an anchor that does poorly in hard sand will invariably do poorly in weed. Since getting the underwater camera I have not seen a lot of weedy anchorages, so there are not a lot of photographs, but the performance in hard sand will give you a good idea which anchors do better.

[Kenomac]

Here's the neighbor's Kobra. Looks like it eventually set on its own, not quite sure how it would have set fifty feet away in the weeds, root and harder soil.

A couple of more pictures to follow on the next two posts. I'm using an iPad with will only post one picture at a time.

[Kenomac]

Another view of the Kobra after four days.

[Kenomac]

Third view of the Kobra, same day and time.

[noelex 77]

This is another Delta.
This particular example has had very little force so this tells us little about the anchor, but I have promised to post photos of every single anchor we have seen since getting the camera. So here it is:

[monte]

Some kobra info in this thread
http://www.cruisersforum.com/forums/...ts-146901.html

[noelex 77]

This was the result after the Bugel moved.

It is very similar to the first drop, although it was not given quite as much force this time.

The wind had reversed 180° here as you can see from the chain, but it was not strong enough to have any effect on the anchor which was still facing in the original direction. You can see the two holes in the shank I mentioned last time. Drilling these types of holes is not a good idea in my view. It weakens the shank and generally the anchor is better retained with some lashings. However, it is common to see this done on many designs of anchors and it is surprising how rare it is to hear of any problems:




The set looks very good from above, but if you look from the seabed you can see the fluke is not as buried as it first appears. Still an OK result that would likely improve with a bit more force:

[sanibel sailor]

Originally Posted by noelex 77

If you panic at the thought of the chain lifting off the seabed have a look at the angle of the chain on this anchor . Note the chain angle is always much higher than the shank angle. Many people think the shank is pulled up at the same angle as the chain and therefore cannot imagine how an anchor can hold when the chain lifts significantly above the seabed.

In reality, as the anchor buries it forces down the shank despite the upwards force of the chain. The holding will always be better at longer scopes, but what happens underwater is not what many people envisage.

Just my thoughts looking at the pictures.

It seems to me that the chain lines up with the tips of the flukes rather than with the shank. It looks this way on Danforth as well as on the various different convex/concave types photos as well. The force vectors make the chain lineup with the of maximum resistance rather than with the shank.

[noelex 77]

Originally Posted by sanibel sailor

It seems to me that the chain lines up with the tips of the flukes rather than with the shank.

Yes, good observation, but I think this is just coincidental. The chain angle will vary continuously depending on the scope and catenary.

This perhaps illustrates things better. You can see the chain angle to the seabed "X" is much greater than the shank angle "Y". In this case the chain angle "X" was varying with gusts as the catenary was altering, but even with a steady chain angle "X" the shank angle "Y" is always significantly less.

The reason for mentioning this is that skippers think if there is zero catenary at say 5:1 they imagine the shank is angled up at more than 11°. In reality while the chain angle will be more than 11° the shank angle will be less. Thus the anchor works better than would be expected when the chain lifts off the bottom.

Most new anchor breakthroughs have been made by very enterprising individuals. I have a lot of respect for these anchor designers. I would never have the enormous perseverance and patience, but I hope a dissemination of information of how anchors behave on a real seabed when attached to our sized vessels will help develop better anchors in the future.