Rocna- what to buy instead?

[Kelpie]

why should a Rocna hold better than say a Delta with the same blade cross sectional area. In the end, the resistance depends on how much mud / sand etc you have to shift as the anchor drags

I think the idea is that some designs will bury themselves better than others. In the PBO anchor test earlier this year, the new-gen anchors were observed to burrow completely into the sand, shank and all. Other designs remained at the surface. It stands to reason that a deeply burrowing anchor will perform better, not only because the entire fluke area is working, but also because the deeper layers of the seabed will be firmer and offer better holding.

 

[noelex]

The sea bed substrate offers much more resistance as the anchor buries more. The surface material is less compacted and offers less resistance. If the anchor can burry deeper it will hold better.
I think the Delta is a good anchor and very good value for money, but the convex blade offers less resistance than the concave face of the modern anchors such as the Rocna and spade. The Rocna and Manson supreme have also a large blade surface area for their weight.

Combine a concave blade, a deeper setting anchor and some increase in blade surface are and you have a powerful combination that will hold in significantly higher winds. This is the essence of the advantage of the new generation anchors.

I have dived and observed these effects. I have also seen the practical differences when anchored in stronger wind.
A friend only a month or so ago dragged his Delta in only 35K wind (gusting to 50). The anchor was a generous size with appropriate scope and was well set (confirmed by diving )They hit some rocks, but with prompt action managed to sustain no damage.
In the same anchorage my Rocna did not drag. I believe this was not due to any greater skill on my part or even luck, but simply a better anchor. I have seen similar results repeated many times.
There are exceptions, particularly in medium thickness sand or mud, where the anchor type makes less difference, but a better anchor dramatically increases your chances of not dragging. This can seen by diving and looking at the set of anchors and observing those boats that get in trouble and drag.

Some people on this forum have expressed the view that anchor technique is all important.. I wish this was the case. I am at anchor over 300days a year and have been so for the last 4 years, before that I anchored at least 60 days a year going back 15 or 20 years. My wife and I are a good team and we know how to anchor.

The technique needs to be OK, but these skills are easily learned, at the end of the day your safely is in the hands of that lump of steel on the end of the chain. Make it the best you can get.

 

[Sans Bateau]

Second thoughts, I'm not getting into an anchoring debate, just would say, the anchoring we do our Delta works OK.

 

[LadyInBed]

Bent Delta

What size Delta is it?

I note from the Delta Data Sheet that for the 10Kg/22Lb and the 16Kg/35Lb anchor, the shank thickness is the same - 13mm or ½ inch
which surprised me.

 

[macd]

the convex blade offers less resistance than the concave face of the modern anchors such as the Rocna and spade.

This has always struck me, in a layman's way, as inevitable. After all a plough (farming-type), is designed specifically to tear out of the soil, the very opposite of what's desired in an anchor. Clearly there are substantial differences in the geometry, but a plough seems an odd starting point for anchor design.

 

[Sans Bateau]

This has always struck me, in a layman's way, as inevitable. After all a plough (farming-type), is designed specifically to tear out of the soil, the very opposite of what's desired in an anchor. Clearly there are substantial differences in the geometry, but a plough seems an odd starting point for anchor design.

But the anchor has to dig in to start with. I guess a mushroom shape would provide the best holding, but then that would need a lot of help to become effective,

 

[sarabande]

MacD
that's not how an agricultural plough works. Ahead of the board (that's the large shiny curved area) there's a knife or coulter wheel which slices a vertical slot through the ground. At the front of the board, there's a chisel point (a frog) which then slices horizontally through the ground, so that the mouldboard just has to lift the soil, turn it through >90 degrees and tip it over, leaving an empty furrow behind it. This furrow is then filled by the next run.


Any anchor which has sort of mouldboard and keeps turning over the sand or clay like a farm plough, will drag. Anchors need to dig in (so, sharp point at the correct angle to the seabed) and then keep going deep down until the resistance of the seabed / substrate to the share area and angle of presentation is greater than the force on the chain from the boat. Then it stops, and you put the kettle on.


Try putting "anchor" and "test " into youtube and you will see examples of anchors opening a trench and dragging. As well as a variety of anchors doing what they are supposed to do and just digging in.


Mushroom anchors, G, are very different principle. Max area normal to the direction of strain. When they are used on e.g. oil rigs, they have to be dug in, and then allowed to settle for a few days. They are not normally set by dragging.

 

[macd]

MacD
that's not how an agricultural plough works.

I beg to differ. That is how the most primitive ploughs work (and I've used one, pulled by a yak in Tibet). I certainly grant you that there's been a deal of refinement since that design.

My basic point was that any anchor of broadly plough-shaped design seems to me counter-intuitive. That doesn't necessarily make it wrong.

Thanks for the youtube suggestion. Already seen.

 

[sarabande]

my yak driving is distinctly limited in comparison with yours Was yours VSO ?

I do drive a mule about twice a week though. A Kawasaki mule....

 

[macd]

my yak driving is distinctly limited in comparison with yours Was yours VSO ?

'Fraid not so selfless: I was riding a Bullet to Lhasa, like you do. Quicker than a yak (slightly).

Anchors to yak-driving: is this a new pb for Fred Drift?

 

[Liz_I]

No-one has yet mentioned that the modern fast set anchors are more at risk from shaft bend because of their ability to set fast and quick!

Unfortunately Spades are not immune from this phenomenon 2 friends with the same anchor suffered the same problem! Mind you these were aluminium so perhaps there is a world of difference in the strength of the shank between the ally and the steel ones.

We have anchored for years with a CQR, never any problems however with all the talk of the new generation anchors etc the Skipper fancied a change! We do have a steel Spade and it's akin to stepping on the brakes just after they have been serviced!! Obviously we've not tried using it in very varied bottoms yet.

Would agree though anchoring technique is very important it takes a bit of time and patience but if you want to sleep at night....................