Photos of Anchors Setting

[noelex 77]

This makes it clearer.

[monte]

I must admit it wasn't a difficult guess with one hanging from our bow

[Wotname]

Originally Posted by noelex 77

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The one area where I think there may be a significant difference in performance is at short scope. The Rocna is very good on a very short scope, but the Mantus seems exceptionally good. It will take more trials to try and quantify the magnitude of improvement, but my confidence in the short scope performance of the Mantus has already proved useful on occasions.
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Hi Noelex,

Just for the record, what is your definition of "short scope" or even "very short scope"

Giv'me numbers man, I need numbers...

[chasfgr]

Originally Posted by Factor

Thanks

I am not suggesting they sent a modified anchor, but one company did do that to me - so it was worth checking. All I am trying to do is remove variables and identify why some sugar scoop anchors are better than others, It appears that, not surprisingly, a large surface area, flatter, sharper anchor is better than smaller surface area, blunter, less curved anchor.

BTW - any chance of trying it without the roll bar? Greg from Mantus suggests that it should work fine, if it did, it would open up its market to a lot more boats.

I'd second trying it without the roll bar. I'd guess the CoG is below the CoE so it should make no difference.
If so my dilemma (finding an anchor, as light as a 25lb CQR, which fits my boat) is solved.

[chasfgr]

V short scope 2:1
Short scope 3:1
???
Re the inverted Kobra - when first I had my boat it had a Sowester plough - that frequently upset. Anchoring was a nerve-wracking business. At that time Sowester were CQR owners.
Fortunately the cast shank broke during a Mallorcan gale and I replaced it with a genuine CQR.
This leads me to believe that those who castigate the CQR only have experience of the generic plough.

[Kenomac]

I know that it's virtually impossible to photograph an anchor set failure on your own boat, but how often do failed attempts come up with the anchors being photographed that appear well set?

I can tell you from first hand experience with the Ultra now in Sadegna, that it' very common for us and others with various anchor types to have to re-anchor after failed attemps sometimes a couple of times. When we hit sand or mud the set is easy, but in many cases what appears to be sand from the surface turns out to be a hard bottom, sometimes rock or a mixture of stones, plant life etc., so the anchor first appears to set, then it pulls out following a good pull in reverse gear. Very common here. I don't fault any of the anchor designs when this happens, seems to be more of an issue of bottom type awareness for the person doing the setting.... Or just bad luck.

Ken

[noelex 77]

Originally Posted by Wotname

Hi Noelex,

Just for the record, what is your definition of "short scope" or even "very short scope"

Giv'me numbers man, I need numbers...

You do need to take into account the anchoring depth. Chain catanery is overrated, but it does reduce the angle of pull of the shank in the initial setting stage and in light and moderate winds. At short scopes the effect of chain catenary needs to be considered.

For the same scope, catenary is greater when anchoring in deep water, as more chain (and therefore chain weight) is used. So anchors will do better at shorter scopes in deep water.

In the sort of depth I usually anchor (6-10m) I would call a short scope as 3.5-3:1 and a very short scope as less than 3:1. I don't suggest my definition is "correct", but it helps clarify what I mean.

However, all anchors lose holding power as you shorten scope. There is no magical fix for this. The important point is that the effect is not equal with all designs. So anchors that have equal performance when both are at 5:1, can be very different when both at 3:1. An ideal anchor would retain as much holding power as possible as the scope is shortened.

In practice, the holding power often tends to drop off very dramatically as a critical scope is reached where the anchor will no longer set. So even a slight drop in scope from say 3:1 to 2.7:1 may produce a severe loss of holding power. This critical value will vary with bottom type as well as anchor design.

[Pete7]

So you think this is a bit short?

Pete

[Pete7]

Back to a more serious post, no one told me I would need a scrubbing brush with a new generation anchor. Spent a night at Studland, Poole Bay, Uk. I thought it was sand with Eel grass patches. Turns out to be a fine layer of sand and grass over mud. What a mess in the morning, the Rocna had a ball of mud on it which took quite a bit of dunking to remove.

The Delta never did this, perhaps the difference between concave and convex anchors.

Pete

[chasfgr]

Originally Posted by Pete7

So you think this is a bit short?

Pete

Nah,

Just needs someone to go onto the sand and use their boot to pound the flukes in!

[noelex 77]

Originally Posted by Kenomac

I know that it's virtually impossible to photograph an anchor set failure on your own boat

Yes that is true. I could chuck my mermaid overboard before I drop the anchor, but she might not come back .
Besides, we work as a team and it much easier with one on the bow and one on the helm with different responsibilities.

However, if our anchor does not set first go I always note the position and dive to find drag marks after we have anchored. I do the same for other boats. I can usually find them and in many cases identify a cause, like some debris (the drag mark will be different if there is debris under the fluke and often the debris is usually left on the bottom at the end of the drag mark where the anchor is picked up. I can also see the substrate and check for problems like a thin layer of sand over rock.

My Mantus is oversized which helps, but so far it has set and held full reverse first time on every drop for over three months now. A great sign.

I also watch boats anchoring and mentally note the anchors that do not hold on the first drop. You need to take into account the technique and substrate. It is also important to understand that reliability of setting is not the same as holding power. However, there is quite a strong correlation between an anchor's overall performance in a particular substrate and its ability to set first time. Of course setting first time is also a desirable quality in its own right.

[noelex 77]

This was the same Kobra after my mermaid told the skipper about the missing bolt. I am not sure if the skipper replaced the bolt correctly. It may have been a substitute bolt that was too small etc. This would have an effect on the geometry so we should not conclude too much about the Kobra's performance from this result.

The anchor was dropped on the edge of a light weed patch, but the set is not very impressive with lots of heaping up.

[noelex 77]

This was a Rocna in light weed.

Unfortunately, they did not put much force on the anchor. The set still looks a bit precarious, but you can see from the substrate on top of the blade it has at least cut through the weed and is into the sand below.

I would have liked to have seen the result after a bit more force.

[Wotname]

Originally Posted by Pete7

So you think this is a bit short?

Pete

Well it isn't dragging so I guess it's OK

[Wotname]

Originally Posted by noelex 77

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In the sort of depth I usually anchor (6-10m) I would call a short scope as 3.5-3:1 and a very short scope as less than 3:1. I don't suggest my definition is "correct", but it helps clarify what I mean.
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Yes, it certainly does - thanks!