Best Value For Money New Generation Anchor

[snowleopard]

Excellent

And lucky for us these days days the better ones will take good care of you in a wide variety of locations and conditions.

But, however good, no anchor suits all types of bottom. Having a second anchor of a different type is good seamanship. I have anchored in a lot of different bottoms and 90+% of the time my Delta has served me well. The only times it has dragged have been:

Liquid mud bottom (Caribbean hurricane holes) - used Fortress successfully

Kelp, shallow sand over rock - give up and go elsewhere.

 

[Neeves]

But, however good, no anchor suits all types of bottom. Having a second anchor of a different type is good seamanship. I have anchored in a lot of different bottoms and 90+% of the time my Delta has served me well. The only times it has dragged have been:

Liquid mud bottom (Caribbean hurricane holes) - used Fortress successfully



Kelp, shallow sand over rock - give up and go elsewhere.

+1

different location, identical issues

 

[NormanS]

Here are 3 very popular anchorages with not a lot of swinging room, and where the wind can blow a hooligan. ( totally inverting a Dragonfly 8m. tri anchored in the second )

I'm interested in which, where and how the assembled panel would deploy anchor(s) in each.

I know nothing about Dandy Hole, but regarding the other two, Puilladobhrain, and Loch na Cuilce, I have anchored innumerable times in each over the past 60 years. Puilladobhrain suffers from its own popularity, and frequently there are too many boats anchored there, for it to be safe if severe weather is likely. In normal weather, it is a very pleasant sheltered anchorage, and should present no great challenge. If, however, it's busy, and bad weather is on the cards, avoid it like the plague. There are plenty of other good anchorages nearby.

Loch na Cuilce, the inner part of Loch Scavaig, is a wild and dramatic place. Being surrounded by high steep cliffs, which can generate fantastic vertical downdrafts, means that it can be an exciting, and sometimes scary place to be at anchor. From many years of observation, I would say that a SW F6 out clear of the land, tends to come into the inner anchorage as a SE F8. Not the best recommendation for an anchorage. On the other hand, in genuinely quiet conditions, it can be idyllic, with the sun's heat reflected from the dark rock, making it really warm.

In both these anchorages, normal anchoring techniques should be adequate, assuming your ground tackle is appropriate for the size of boat. Loch na Cuilce is less likely to be crowded overnight, as many people pay a short visit, and go elsewhere for the night. Again, if I felt that there were too many boats there, for the often erratic winds, I would clear out. Again, there are other places not far away.

 

[GHA]

Interesting stuff. You would have thought this would have been perfected 150 years ago, but apparently not.

View attachment 69822

:encouragement:

Thanks for posting, really interesting.

 

[AngusMcDoon]

...with the sun's heat reflected from the dark rock, making it really warm.

Radiated

 

[thinwater]

:encouragement:

Thanks for posting, really interesting.

You are welcome.

The interesting corollary is that the one way I am most likely to guess the type of anchor is during recovery. In general, an anchor that is good at short scope is a bugger to break out and an anchor that is easy to break out is poor at short scope. It is a matter of how it reacts to up-lift.

 

[Neeves]

If I interpret correctly Thinwater has set his various anchors and measured the tension used to set, the holding capacity. He has then increased the rode angle and measured the break out loads.

Correct me if I'm wrong.

So if you have 40hp of auxiliary diesel and can develop a tension in the rode of 400kg then for what Thinwater describes as Scoop anchors the reduction in breakout load does not vary much with 'design? or size?. Basically at Thinwater's extreme of short scope the breakout load is half the setting load. It does not matter how big the anchor is, the setting tension (and thus hold) is defined by the engine and setting rode scope - not by the size of the anchor. So - as both the large and small anchor would both be set to 400kg - their breakout loads, if same design, will be similar (at around 200kg).

My conclusion is that if you want to anchor at short scope then you need to be using, what looks to be, a Fortress or Guardian - not a Scoop style. The size of your Scoop style makes not an iota of difference (except for the weight of the anchor itself). But at short scope you are sacrificing a significant amount of hold - and consequently it does not appear to be a very sensible practice (no matter which anchor you use).

I have to question why some have been advocating anchoring at short scope and using this as justification for carrying large anchors. Basically the whole concept, constantly repeated, is (or was) untested nonsense. Now its been tested it is definitely dangerous nonsense. Its encouraging to have some data to contradict the gut feel.

Jonathan

edit

The large anchor theory has not be shown to develop more hold, for an anchor of the same design in the same seabed as hold is defined by engine capacity or windage. The large anchor is no safer at short scope than a small anchor. The large anchor adds little weight to the bow, but does make a bigger hole in your wallet.

I wonder which other factors are still be be argued as the reason to buy an anchor bigger than that recommended by the anchor maker? and especially carrying an anchor twice the size recommended?

Thinwater's simple graph illustrates that design is a much greater factor should you want to anchor at short scope and Fortress tests in the Chesapeake underline that an anchor that is good in sand maybe a complete disaster in thin mud. Slowly this idea that size matters is being slowly but surely hit on the head - if you want certainty carry a cross section of designs - and be prepared to use them.

There may be factors that make a bigger anchor better - but no-one has mentioned them, yet, and no-one has certainly produced any evidence, apart from questionable gut feel, to support their ideas.

close edit

 

[thinwater]

If I interpret correctly Thinwater has set his various anchors and measured the tension used to set, the holding capacity. He has then increased the rode angle and measured the break out loads.

Correct me if I'm wrong....

Slightly.

I set the anchors at long scope, just enough to engage the fluke up to the shank. I believe this is typical of an anchor set with some chain even at short scope. This was never more than a small fraction of the holding capacity, even at short scope, and represented no more than a mild power set. Except for very short scope, they all buit more holding capacity. The chain will keep the pull low enough that the initial set is similar at all but very short scope. I did not test below 3:1 scope because I was not sure this would be true and because the spread in data gets ridiculous at scope less than 3:1.

These tests were run using fiber rode, so the angle at the bottom is directly related to scope with no catenary. Obviously, all-chain always modifies the angle, but that is different math.

After setting the anchors, the scope was reduced to the require angle and we pulled.

This is how the large stockless data was described as well. I also compared data from others, and it matched up pretty well.

I normalized the data for size and type and disguised the brands because that just complicated matters. In fact, the anchor that showed the poorest shorts scope % was NOT the weakest, since it had a higher long-scope starting value. Variables like thinner metal can lead to greater fluke area.

Like most anchor testing, the results were all over the place. The relation between scope and holding capacity, however, was robust.

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What happens if you set HARD at long scope, and then shorten up? I did not study that directly. I'm sure the result depend very strongly on how cohesive the soil is. In loose coral sand, the deep set will only help a little. In sticky mud... If you've ever tried to recover a Fortress after hitting it with over 1000 pounds you know what I mean.

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Some test protecoles pull anchors at constant scope. Others start at long scope and pull the anchor to the boat or winch platform. If the test is run in this latter way, the farther the anchor drags, the lower the scope, until they all fail.
* The first method often uses a tug boat. They have trouble pulling at a controlled rate and can produce terrible numbers if not careful. This is a terrible approach, IMHO. I have run tests at constant scope, but I do it by winching the boat forward against a big anchor, so I can control the pull rate. More time consuming, but the data is MUCH better.
* The second method really favors an anchor that goes deep, quickly, since scope is diminishing. So long as it is started at long scope, it's OK, but it is not reliable at short scope.