Mantus Anchor or Rocna ?

[jcapo]

Originally Posted by snort

Rocna and Mantus anchors look so similar. Is there really a difference?

Looks like more fluke area to me.

[Cotemar]

Originally Posted by jcapo

Looks like more fluke area to me.

Great picture. I took that a few years ago.

As Panope said the Mantus do weigh less than advertised.

Also bit rough on the finishes.

You can not beat the Mantus fluke surface area.

If Mantus can iron out those few issues they will be a top contender in my book.

[mikereed100]

We put a Rocna on the boat 6 years ago and, after 18,000 miles and countless nights at anchor in soft mud, sand, rock and weed can say that it is a fantastic anchor. The great majority of the time it set immediately in whatever bottom we were in. A vast improvement over the CQR that it replaced. However, there were a small handful of times when it struggled just a bit in mud and weed. I recall one time in thin weed where I had my wife put out 3:1 scope in 30 ft of water then slowly back down while I watched from in the water. The anchor dragged across the bottom until the fluke had collected enough weed that I felt it was not going to set. A couple other times we had to try 2 or 3 times to get it to set in weed or soft mud. To me, an important feature of an anchor is that it should set quickly on short scope in any substrate. Picture losing power or steering in tight quarters on a windy day. Given this and based on video of anchors setting in weed, we replaced our beloved Rocna with a Mantus in the hopes that it will perform better in those rare cases where the Rocna struggled. I'll try to report back when we have tested it. There will, unfortunately, be no photos as the water is too cold to support life just now.

[Gradient]

Have owned both, the Rocna on a 45ft mono and the Mantus on a 45ft cat. I think the mantus has a slight edge on its ability to set in weed. Granted I've never had them side by side but a few times I had trouble to set the Rocna in weed but never with the Mantus, it just seems to "bite" every time and almost always sets in its own length with a very satisfying bounce on the bridle. Two years of almost daily use and (touch wood) we have never dragged. My vote is Mantus but I don't think you'd go far wrong with Rocna.

[mikereed100]

Side by side of Rocna 33kg and Mantus 35kg. The fluke size is not much different, but the shaft length and hoop diameter of the Mantus are significantly bigger, which may account for it's slightly easier setting.

[DumnMad]

Originally Posted by jcapo

Looks like more fluke area to me.

The Mantus' much larger area of hoop etc would be great for drag resistance in deep soft mud.
However I wonder if the area would reduce the depth into mud it could dive during a storm.

Maybe a better mud anchor in most winds but not better in a storm?? (Capacity goes up with square to cube of depth.)

[Cotemar]

Originally Posted by mikereed100

Side by side of Rocna 33kg and Mantus 35kg. The fluke size is not much different, but the shaft length and hoop diameter of the Mantus are significantly bigger, which may account for it's slightly easier setting.

Great picture.

Nice to see the side by side.

Looks like the Rocna 33kg and Mantus 35kg have about the same surface area

I wonder why the 20kg Rocna and Mantus anchors are so much different.

[malbert73]

Originally Posted by Fortress

We noticed the same during 8 days of pulling anchors off of Solomons, MD aboard the 81-ft Rachel Carson R/V. For whatever reason the Mantus seemed to be able to self right itself better in the soft mud. Based on your experience, you gave a reason for this about the Rocna and you might very well be correct.

However, we bent the much larger Mantus roll bar during one test and I would venture to say that it is not as strong as the Rocna roll bar.

Yes, I agree. Like most Chesapeake based sailors we also carry a fortress which generates the most straight line holding power by far😀

How do you think the strength of the fortress vs mantus shank compare? Both companies offer replacement of this should happen. Both can have shank replaced without replacing whole anchor so a spare on theory for each could be stored on board for far off cruising..


Sent from my iPhone using Cruisers Sailing Forum

[Fortress]

Originally Posted by malbert73

How do you think the strength of the fortress vs mantus shank compare?

While the Mantus is made from steel and the material is typically stronger, aluminum-alloys can be machined and thickened to insure that they can absorb and disperse a load, and in turn compensate for a difference in material strength.

The US Navy noted this in their test report after the Fortress was tested against high strength steel Danforth, NAVMOOR, and STATO anchors. During one pull test, the 45 lb FX-85 held to 10,200 lbs of pull, at which time the test was stopped, and the shank was bent during retrieval. From their conclusions page:

The fact that the FORTRESS anchors incurred no significant structural damage at such high holding ratios suggests that the anchors have been extensive engineered from both the hydrodynamic and structural standpoints.

The bent shank that resulted from retrieving the FX-85 anchor served to illustrate one potential drawback of using aluminum as an anchor material for a "streamlined" anchor, i.e. its relatively low yield strength and elastic modulus (compared to high strength steel) make the anchor susceptible to permanent deformation under concentrated or unanticipated loading conditions. A high strength steel such as HY-130 , for example, has nearly four times the yield and strength and three times the elastic modulus of unwelded 6061 T-6 aluminum alloy (used for FORTRESS anchors.)


Under anticipated loading conditions, NAV-X [Fortress} has compensated for aluminum's susceptibility to deformations through careful structural design of their anchors.

However, in the case of the FX-85 anchor retrieval, only an extremely high-yield material (such as HY-130) or an extremely thick "non-streamlined" shank (such as the STATO anchor has) might have prevented the deformation that occurred.

Alternatively, NAV-X has designed the FORTESS anchors to readily assemble and disassemble (only two bolts are used to hold components together), so that damaged components can be easily repaired or replaced."

[DumnMad]

Under overload conditions bending and yielding is the preferred form of engineering failure.

When I see the shank bent under extreme load I think good engineering. Main points are; you know its been overloaded and it didn't have sudden weld failure

[cortezsailor]

I use a Rocna 33 at around 75 lbs for my main anchor. Its storm size anchor with 300 ft of G40 Chain and 20 feet of 8 plait line. I have chosen the Mantus 65 lb as my back up to the Rocna . For this I have a 100 feet of G40 chain and 250 feet of 8 plait line. The nice thing about the Mantus anchor is I can take it apart so it makes storage a bit easier. Both hold great on a 39 foot 26 000 lb displacement boat.

[Fortress]

Originally Posted by mikereed100

Side by side of Rocna 33kg and Mantus 35kg. The fluke size is not much different, but the shaft length and hoop diameter of the Mantus are significantly bigger, which may account for it's slightly easier setting.

Here's a couple of images from our factory with another comparison of a similarly-weighted Fortress model in between a Mantus and Rocna that we have from the Chesapeake Bay testing.

image hosting 12mb

photo sharing websites

[mikereed100]

Originally Posted by Fortress

Here's a couple of images from our factory with another comparison of a similarly-weighted Fortress model in between a Mantus and Rocna that we have from the Chesapeake Bay testing.

image hosting 12mb

photo sharing websites

Unfortunately, I can't get those links to work on my browser. I'm curious; how did you manage to bend the hoop on the Mantus during testing?

As an aside, we were anchored the other night in a spot that can be a little challenging for anchors. We watched as a 40' sloop came in and tried, unsuccessfully, to set their Delta. They worked at it for 2 hours, then, as it was getting dark, they swapped The Delta for a Fortress that they had on the stern. It set immediately and they were finally able to get some rest.

[Fortress]

Originally Posted by mikereed100

I'm curious; how did you manage to bend the hoop on the Mantus during testing?

We must have gotten it stuck on something in the testing area, possibly a log. Obviously it had to be a good size to engage and load up the huge roll bar, but nothing came up with the anchor.

[groundtackle]

If you're at the Vancouver boat show this week till Sunday (booth 323) or Seattle (booth east 820) January 27 through February 4th come and check our booth. We have samples of all our product line for you to play with and see what all the fuss is about. The EXCEL and SARCA anchors are featured in Steve 'Panope's' videos, thanks again Steve.
Look fwd to meeting a few of you.
Chris, Nick and John.