Photos of Anchors Setting

[noelex 77]

We are still at the same anchorage.

The wind has been switching direction, which unfortunately means an anchorage with close to 360 degree protection is needed unless we want to move at 2am, which quickly loses its appeal.

The wind has not been strong, although it has been 30 knots most days and there have been constant forecasts of 40 knots+ (not eventuated). To give you some idea of the problems this time of year, one of our favourite forecast sites (UGrib) says tomorrow will have 17 knots NE. The other one, Windfinder, says 38 knots SE with 46 knot gusts.

The water has been very cloudy and although I have managed a couple of photos from the surface they didn't show much with the anchor looking unchanged.

Yesterday my mermaid went for swim and took a better photo. The anchor has settled a little deeper with the shank and fluke well below the surface. All that can be seen is the top of the roll bar. The Mantus has quite a tall roll bar. Even the slightly lower Rocna roll bar would probably not be tall enough to seen at this same level of bury.

There are a couple of reference marks and the anchor has not moved at all. Unfortunately with this sort of softer substrate any marks caused by rotation get filled in. Most of the strong wind has been from the north and I suspect the anchor has not rotated anyway.

The Xmas decoration has slid down the roll bar and it has been removed so we are not leaving any rubbish behind if it falls off.

BTW I forgot to add we have extended our scope. It is now about 7:1.

[kas_1611]

Blimey Noelex if it digs in any deeper you might hit magma :-)

Have you ever had the Rocna or Mantus move/drag when it is set this deeply or are they pretty much bomb proof once that well embedded?

Keiron

[noelex 77]

I hope we don't hit magma . We are not very far from the volcanic island of Santorini, which supposedly lead to the demise of the Minoan civilisation when it exploded 3000 years ago. The main population centre was over a 100km away from the island so it must have been an enormous eruption.

This is close to the easiest substrate. There is not the tough hard sand layer that is present in many of the anchorages that I have photographed in this thread. Almost all anchors do well and look good in this sort of bottom. It is soft enough that any design of anchor will penetrate, but firm enough to still provide reasonable holding.

In high winds those anchors with only a small blade area can struggle to generate enough resistance, but it takes a lot of force before you see this. Watch for slow drags in this sort of substrate. An anchor struggling will often remain set, but slowly work its way backwards in the stronger gusts. Usually the owner is unaware.

The roll bar is the last part of the anchor to bury. It only starts to get buried when the fluke and almost all the shank are under the substrate. The Mantus has a big roll bar so the fluke is currently buried a long way down.

I took the photo below simply by placing the Mantus roll bar on the almost identical weight Rocna (57 and 55 kg respectively). It gives an impression of the relative size difference of the roll bars on these two anchors.

Let's hope the magma layer is a bit deeper .

[kas_1611]

Yes the Santorini eruption was a massive one. Actually 4 times the volume of rock was ejected than Krakatoa and it did destroy the Minoan civilisation. It was what Geologists (like me) call a Plinian type eruption, which are the most violent type, and erupted 60 cubic km or 14 cubic miles of material high into the Stratosphere. Including all the material erupted the total mass may have exceeded 100 cubic km or 24 cubic miles!! it also created a tsunami 150m or ~500ft high that devastated Crete over 100km or 60miles away. The central bay remaining in modern Santorini gives an idea of the size of the original caldera and an idea of just how much rock was ejected.

If you want a little more info check the Wiki page Minoan eruption - Wikipedia, the free encyclopedia for more details of the impact the eruption had, or may have had, around the globe.

Finally that is a BIG roll bar and a great comparison between the two different models. Mantus aren't made in Texas are they? As everyone knows everything is bigger in Texas ;-)

Keiron

[Jim Cate]

G'Day Nolex,

That's an interesting picture! Just curious... now that you have used both, do you think that the much wider roll bar has a positive, negative or no influence on the anchor performance? If I understand the purpose of the RB, it is to turn the anchor over ensuring that the tip engages the sea bed no matter how the anchor settles initially. I've not heard of Rocnas (or any other roll bar anchor) failing to do that, so the big difference in design is interesting to me.

Jim

[downunder]

Originally Posted by noelex 77

I hope we don't hit magma . We are not very far from the volcanic island of Santorini, which supposedly lead to the demise of the Minoan civilisation when it exploded 3000 years ago. The main population centre was over a 100km away from the island so it must have been an enormous eruption.

This is close to the easiest substrate. There is not the tough hard sand layer that is present in many of the anchorages that I have photographed in this thread. Almost all anchors do well and look good in this sort of bottom. It is soft enough that any design of anchor will penetrate, but firm enough to still provide reasonable holding.

In high winds those anchors with only a small blade area can struggle to generate enough resistance, but it takes a lot of force before you see this. Watch for slow drags in this sort of substrate. An anchor struggling will often remain set, but slowly work its way backwards in the stronger gusts. Usually the owner is unaware.

The roll bar is the last part of the anchor to bury. It only starts to get buried when the fluke and almost all the shank are under the substrate. The Mantus has a big roll bar so the fluke is currently buried a long way down.

I took the photo below simply by placing the Mantus roll bar on the almost identical weight Rocna (57 and 55 kg respectively). It gives an impression of the relative size difference of the roll bars on these two anchors.

Let's hope the magma layer is a bit deeper .

Great comparative picture and does point the way if one was in the market for a roll bar anchor.

cheers

[JPA Cate]

downunder,

Forgive me for not understanding, please, but which roll bar would you prefer? and if you would be so kind, could you explain why?

My reason for asking is that we have a Manson Supreme (giant roll bar); and yet Noelex has had great results with his way oversize Mantus.

Ann

[downunder]

Anne,

Firstly let me say I do like the Manson Supreme and much prefer it to the Rocna particually after they changed the quality of their shaft steel.

It suggests to me that the Mantus with the thinner roll bar looks like it will penetrate and bury more readily than the Rocna and on that basis if I was purchasing a roll bar anchor I would certainly consider a Mantus.

Nolex would perhaps be much better able to comment with his actual experience but I note he is in no rush to go back to his ROCNA in those winter storms in the Med.

However if I do purchase a vessel in Australia I do favour the SARCA Excel without a rollbar.

Cheers

[Wotname]

Originally Posted by noelex 77

We are still at the same anchorage.

The wind has been switching direction, which unfortunately means an anchorage with close to 360 degree protection is needed unless we want to move at 2am, which quickly loses its appeal.

The wind has not been strong, although it has been 30 knots most days and there have been constant forecasts of 40 knots+ (not eventuated). To give you some idea of the problems this time of year, one of our favourite forecast sites (UGrib) says tomorrow will have 17 knots NE. The other one, Windfinder, says 38 knots SE with 46 knot gusts.

The water has been very cloudy and although I have managed a couple of photos from the surface they didn't show much with the anchor looking unchanged.

Yesterday my mermaid went for swim and took a better photo. The anchor has settled a little deeper with the shank and fluke well below the surface. All that can be seen is the top of the roll bar. The Mantus has quite a tall roll bar. Even the slightly lower Rocna roll bar would probably not be tall enough to seen at this same level of bury.

There are a couple of reference marks and the anchor has not moved at all. Unfortunately with this sort of softer substrate any marks caused by rotation get filled in. Most of the strong wind has been from the north and I suspect the anchor has not rotated anyway.

The Xmas decoration has slid down the roll bar and it has been removed so we are not leaving any rubbish behind if it falls off.

BTW I forgot to add we have extended our scope. It is now about 7:1.

Gosh, don't worry about the magma, worry about getting that anchor back on board!!!

[noelex 77]

Originally Posted by Jim Cate

G'Day Nolex,

That's an interesting picture! Just curious... now that you have used both, do you think that the much wider roll bar has a positive, negative or no influence on the anchor performance?

The Mantus has some "wings" attached to the rear of the fluke. This widens the back of the fluke and results in a larger roll bar. The major advantage is that when resting on the wider roll bar, it forces the tip into a more aggressive setting position. This places more pressure on the toe which allows the anchor to cut into difficult substrate like hard sand and (hopefully) weed better. I also suspect it is the major reason for the excellent short scope performance.

The Rocna and Manson Supreme have some skids on the underside of the fluke designed to achieve the same objective, but the resulting setting position of the anchor is less aggressive as you can see in the photos. The drawback of the wings is that it makes the anchor wider. Together with the longer more tapered fluke it is a big anchor.

These photos show the Rocna and Mantus in their setting position and you can see the difference in the setting attitude and the angle of attack of the toe as a result of the wider roll bar.

This is the Mantus:





The Rocna:

[Jim Cate]

Thanks for those pix, Nolex. they make a graphic image of the differences between the two designs. One question I'm left with: the Mantus RB is of a smaller cross section than the Rocna, but of a larger span. Can you estimate the projected area of the two systems? That might give an idea of how much drag the RB adds... drag that inhibits burying. That's again just my curiosity showing, for the Mantus certainly has shown itself capable of deep burying in your photos.

All good stuff... again thanks for providing some reasonably objective data in the anchoring wars.

Jim

[noelex 77]

Originally Posted by Jim Cate

One question I'm left with: the Mantus RB is of a smaller cross section than the Rocna, but of a larger span. Can you estimate the projected area of the two systems?

No problems. I will measure the Rocna and the Mantus roll bar (next time it is up).

[noelex 77]

I did some measurements while hanging over the bow .

The 57kg Mantus roll bar is 32.5mm in diameter with a length of 1.33m.

The 55 Kg Rocna has a roll bar is 42.5mm in diameter with a length of 0.92m to the fluke. It extends under the rollbar by a further 6.3 cm on each side.

The total cross sectional area of the roll bar is almost the same for the two anchors.

The Mantus at 0.043 m2 and Rocna at 0.045 m2. The Mantus roll bar is thinner and taller so if the roll bar is partially buried the drag from the Mantus will be significantly less.

Take into account the measurements for the Mantus were done leaning over the bow roller while the thunderstorms and ligtning made life interesting, so take these results as reasonably rough.

The roll bar does not start to bury until the fluke is completely covered and the shank is almost totally buried so in most sets the drag of the roll bar will be minimal.

[Jim Cate]

Originally Posted by noelex 77

I did some measurements while hanging over the bow .

The 57kg Mantus roll bar is 32.5mm in diameter with a length of 1.33m.

The 55 Kg Rocna has a roll bar is 42.5mm in diameter with a length of 0.92m to the fluke. It extends under the rollbar by a further 6.3 cm on each side.

The total cross sectional area of the roll bar is almost the same for the two anchors.

The Mantus at 0.043 m2 and Rocna at 0.045 m2. The Mantus roll bar is thinner and taller so if the roll bar is partially buried the drag from the Mantus will be significantly less.

Take into account the measurements for the Mantus were done leaning over the bow roller while the thunderstorms and ligtning made life interesting, so take these results as reasonably rough.

The roll bar does not start to bury until the fluke is completely covered and the shank is almost totally buried so in most sets the drag of the roll bar will be minimal.

Interesting... thank you for making the effort, especially with Jove hurling bolts at you! Sounds like there is no significant difference in frontal area between the two, but possibly in when the roll bar starts to impede burying.

Some of Mantus's choices in the design are becoming more clear to me (I think), and my overall impression of the anchor are improving.

Thanks again, mate!

Jim

[noelex 77]

We finally escaped the anchorage with a reasonable forecast for a couple of days. There was a good deal of thunderstorm activity around when we left.

We arrived at our chosen anchorage to find a local fishing boat also anchored there. The anchorage is tight and with our neighbour occupying the prime spot, a scope of only 3:1 was possible in 4.5m of water.

As we were setting a large thunderstorm came through and shifted the wind about 40 degrees. Unfortunately the shift was same direction as our prop walk which meant the anchor was pulled over a wide arc while it was digging in.

Anchors hate setting with a change in direction of pull and with the shortish scope I was expecting a poor set.

This was the very impressive result. The Mantus has taken slightly longer to set than normal. It normally sets in a remarkably short 2-3 feet and this was about 4 feet. Surprisingly it is completely level and well buried. It has managed to bury the fluke and shank completely.