Mantus Anchor or Rocna ?

[Celestialsailor]

Originally Posted by EighthWonder

I keep hearing this kind of experience with the Rocna. That's fantastic! I can't wait to try mine. ;-)

I have not had mine do anything weird this entire trip south. Even in La Paz, where they call the anchorage..."the La Paz waltz", due to it's powerful ebb and floods.
This is sort of a strange thread since the Rocna, Manson and Matus are virtually the same. Owners of all of them report satisfied results, that I have talked to. My personal choice was based on quality of welds and the reasoning behind bolting together of the Mantus. Which seemed to me to be more of a shipping solution for them than any anchoring feature.
While in Dan Point, I was warned of the hard clay bottom. But I managed to even pull a chunk of that bottom up the next morning as I weighed anchor.

[JPA Cate]

The other day, during a wind burst which happened as we were anchoring just as the front was arriving, we watched a boat of around 50 ft. drag. It struck two boats, then stopped when it came head to wind alongside the second one.

After aid came--its crew were ashore--we saw that the anchor that had dragged was a Rocna, which Jim judged too small for the boat, which had its bimini and awning up, so a lot of sail area.

From what I saw, I do not think the Rocna kept on diving as people here sometimes suggest; it just pulled out. Our maximum gust was only 35 knots. We did not drag at all with our Manson 60 lb. Have never drug in that anchorage. The holding is excellent. We suspect there was too little scope out, but did not ask.

Ann

[Celestialsailor]

Yes....more critical than anchor design will be and has always been proper deployment. This also includes proper sizing of all the ground tackle...amchor size, chain size, scope and setting.

[Uncle Bob]

Originally Posted by Ann T. Cate

The other day, during a wind burst which happened as we were anchoring just as the front was arriving, we watched a boat of around 50 ft. drag. It struck two boats, then stopped when it came head to wind alongside the second one.

After aid came--its crew were ashore--we saw that the anchor that had dragged was a Rocna, which Jim judged too small for the boat, which had its bimini and awning up, so a lot of sail area.

From what I saw, I do not think the Rocna kept on diving as people here sometimes suggest; it just pulled out. Our maximum gust was only 35 knots. We did not drag at all with our Manson 60 lb. Have never drug in that anchorage. The holding is excellent. We suspect there was too little scope out, but did not ask.

Ann

Ann this was the experience that I had with my rocna, I found that it was not well suited to the mud of one of my favourite anchorages.
I always had at least 5:1 scope but there were a number of times that it did not hold very well, even in moderate winds.
To be fair to rocna I feel that the size recommended by the rep at the sydney boat show (15 kg) and purchased was too small for the boat.
Rex"s excell, 5 kg heavier, holds first time and comes up clean every time.

[DoubleWhisky]

Originally Posted by Uncle Bob

Ann this was the experience that I had with my rocna, I found that it was not well suited to the mud of one of my favourite anchorages.
I always had at least 5:1 scope but there were a number of times that it did not hold very well, even in moderate winds.
To be fair to rocna I feel that the size recommended by the rep at the sydney boat show (15 kg) and purchased was too small for the boat.
Rex"s excell, 5 kg heavier, holds first time and comes up clean every time.

From Rocna sizing chart for Your (quite heavy and high windage boat) Rocna 20 kg is the bare minimum. 15 kg have a lot to small fluke area to keep You in the mud, especially not very thick one.
Rex's own recommendations for Excel sizing are exactly the same for my boat as Rocna's. Probably You need the same weight for Excel and for Rocna.

[DoubleWhisky]

Originally Posted by Ann T. Cate

The other day, during a wind burst which happened as we were anchoring just as the front was arriving, we watched a boat of around 50 ft. drag. It struck two boats, then stopped when it came head to wind alongside the second one.

After aid came--its crew were ashore--we saw that the anchor that had dragged was a Rocna, which Jim judged too small for the boat, which had its bimini and awning up, so a lot of sail area.

From what I saw, I do not think the Rocna kept on diving as people here sometimes suggest; it just pulled out. Our maximum gust was only 35 knots. We did not drag at all with our Manson 60 lb. Have never drug in that anchorage. The holding is excellent. We suspect there was too little scope out, but did not ask.

Ann

Ann, my Rocna dives deep, I can assure You. I checked it many times.
It need something hard under to stop it diving before it would be buried for several feets down.
On the other hand I do believe the undersized one will drag slowly, not dive deep.
Apparently (from others experience) it is "weight sensitive", You shouldn't try undersized one.
From my own experience it is sensitive to proper setting procedurę.
I described it in detail somewhere earlier.
Last thing (probably biggest disadvantage of Rocna) it is "scope sensitive".
I know that the scope should be 6:1 or more, and I do believe that all-chain rode is much advisable. I would not compare Your Mason to the dragging Rocna by the way. I'm sure You had properly sized, well set anchor, on proper scope and good rode. What to compare???

Best regards to You and Jim

Tomasz

[EighthWonder]

Originally Posted by DoubleWhisky

Ann, my Rocna dives deep, I can assure You. I checked it many times.
It need something hard under to stop it diving before it would be buried for several feet...

From my own experience it is sensitive to proper setting procedurę.

Last thing (probably biggest disadvantage of Rocna) it is "scope sensitive".
I know that the scope should be 6:1 or more, and I do believe that all-chain rode is much advisable.

Tomasz

May I ask:
If you shorten your scope after your Rocna has set will it will continue to dive, or will it pull out?

[DoubleWhisky]

Originally Posted by EighthWonder

May I ask:
If you shorten your scope after your Rocna has set will it will continue to dive, or will it pull out?

When Med mooring (what I do most of the time) it is no option to shorten the scope.
When anchored already, I sometime shorten a scope after considerable time given to the anchor to dive initially and after some additional power setting. It is just to allow some more place around for others.
On the other hand I do not dare to enter the anchorage with limited space and several boats around and anchor at 4 : 1.
And yes, I remember I tried shortening to 3 : 1 once and it dragged. I didn't try to reset, as I was anyway about to leave. It was only lunch/bathing stop

You probably may well call me overcautious about anchoring, but I really do like very well set hook on as long rode as possible

I do not think Rocna dive more than several feet on average bottom. It just holds. Of course, if You stay in place for long time (many days) it would bury deeper and deeper, but not so much. However extracting her from the seabed is somewhat more time consuming after a five days, than after two days

Best regards

Tomasz

[noelex 77]

The best anchors in mud is the Fortress, particularly when set at the 45 degree fluke angle setting. The only precaution to consider is if there is likely to be a change in the direction of pull, but the risk of problems resetting are less in a softer substrate.

Danforth anchors can also be very good, but make sure the geometry and design is correct.

New generation concave anchors are next best. The large projected fluke area provides high resistance.

Convex anchors can work well, but if there is not a firmer substrate under the softer mud the lower resistance of the convex shape offers less resistance. A slow drag is quite common in strong wind conditions. At least this slow drag is easier to manage, but it can create problems.

Overall in soft substates careful anchor design is less critical. All anchors will set and burry. A large projected surface area tends to be the most important factor in staying put.

If anchoring in shallow water the deep penetration of the anchor in a soft substrate can increase the angle of pull on the anchor shank. More scope than normal may be needed to compensate.

[EighthWonder]

Originally Posted by DoubleWhisky

You probably may well call me overcautious about anchoring, but I really do like very well set hook on as long rode as possible

Best regards

Tomasz

Thank you...

It's scary how many have been ready to drop anchor within my swing when I have proper rode out. When I ask them to move if the don't want me berthed in their stateroom through the night they look at me like I have two heads.

I realize why they react that way when they move over...set their anchor...then pull in their rode until they're sitting right over top of their anchor!!!!! Amazing how more aren't waking up on the rocks...

[DoubleWhisky]

Originally Posted by noelex 77

Convex anchors can work well, but if there is not a firmer substrate under the softer mud the lower resistance of the convex shape offers less resistance. A slow drag is quite common in strong wind conditions. At least this slow drag is easier to manage, but it can create problems.

I think that the weakest point of convex shape is the bottom with soft substrate over really hard layer two, three or four feet below.
Mud, sand/gravel over hard chalk, hard pressed clay, flat rock. A lot of such a places in Ionian for example, less in Dodecanese, but they are here and there. Concave of the same fluke area will probably held earlier (less buried) than convex. On the other hand I believe that convex may be easier in working the hook through the weed or grass, especially if we compare with rollbar concaves.

Best regards

Tomasz

[malbert73]

I think hairs can be split certainly between the next gen concave anchors. I bought a mantus because the roll bar is hollow, and the shank is slightly lighter, than a manson or rocna. Therefore for the same weight of anchor, it seems to have larger fluke area. I also like the wider spaced roll bar which is less likely to clog perhaps. A big perhaps.
I anchor more in mud/sand/grass than coral or rock.
If I anchored more in firm or rocky bottoms, I would have bought a manson perhaps because the shank seems bulletproof and heavy, perhaps at the cost of the fluke area. Just don't like the rock slot- seems like waste of weight. Also like rocnas. No need to be ridiculously militant and passionate. All would be fine for me I think. in reality it probably is a small window of difference in performance in different substrates for these.

The old 35 lb genuine bruce I have is bulletproof in construction, and sets instantly, but I've had slow drag in 25-30 knot squalls because so much more weight is elsewhere but in the flukes.

My danforth HT 20 lb anchor probably has the highest holding potential if set correctly, but I've had drag suddenyly when fouled with weeds, sticks, or resetting.

[Cotemar]

Originally Posted by malbert73

I bought a mantus because the roll bar is hollow, and the shank is slightly lighter, than a manson or rocna.

Ah. Um. Mantus, Manson and Rocna all have hollow roll bars, but we will keep this between you and me.

[malbert73]

Originally Posted by Cotemar

Ah. Um. Mantus, Manson and Rocna all have hollow roll bars, but we will keep this beween you and me.

Thanks for the info. I was misinformed by a pro rocna person who insisted that the roll bar was stronger because it was solid.

Always appreciate the snarky tone in the reply!

[Cotemar]

Originally Posted by malbert73

Thanks for the info. I was misinformed by a pro rocna person who insisted that the roll bar was stronger because it was solid.

Always appreciate the snarky tone in the reply!

It's all fun, mate. No worries