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Old 30-08-2019, 02:41   #16
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Re: Rocna roll bar

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The Rocna shank is not that much different from a Delta etc, it just has wider flukes. Why would a roll bar right an anchor?
The Delta primarily uses ballast to orientate the anchor in the correct setting position and make the anchor unstable in positions where it will not set.

The Rocna uses the roll bar instead of the high amounts of ballast. Without the requirement for a large ballast chamber, the fluke, especially the leading part can be much thinner, assisting penetration in hard substrates and weed. The absence of the large amount of ballast weight means the Rocna fluke area can be made larger compared to same weight Delta anchor. This larger fluke area improves holding in softer substrates.

The Rocna fluke is concave rather than convex.

The above is very simplistic, there are many other refinements, but the Delta and Rocna are very different despite similar shaped shanks. They use a different primary mechanism for adopting the correct setting position.

The Rocna is a much better anchor than the Delta. Trying to make a Rocna more like a Delta is going backwards in my view.
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Old 30-08-2019, 03:26   #17
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Re: Rocna roll bar

So, OP, you posed a question about removing the roll bar from your Rocna. Several knowledgeable folks, sailors who have personally investigated the behavior of roll bar anchors in action, have advised that it isn't a good idea.

You disagree and dismiss their opinions. OK, your mind is made up, and you are gonna do it. Fine... we all hope that you get the results that you wanted. I just wonder why you bothered to post the question if you ain't gonna listen to the answers?

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Old 30-08-2019, 03:29   #18
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Re: Rocna roll bar

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I get it with the Mantus, it's very wide and needs help. The Rocna shank is not that much different from a Delta etc, it just has wider flukes. Why would a roll bar right an anchor? You are not not pulling it sideways. The angles in the shank are such that it has tendency to pull the leading edge down, not up anyway.
We have a Canadian Rocna (25kg, ser #125), and it never lands upside down.
You are pulling it sideways. A Rocna, and even a Bruce will always land on their side. As you pull them the tip digs in and the anchor rights itself. The Rocna with the help of the roll bar.

Why anyone would think they know much better than the designer of the best anchors around is lost on me.
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Old 30-08-2019, 04:07   #19
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Re: Rocna roll bar

I see the complaint about a Rocna filling with grass or mud.

IMHO one of the advantages of a Mantus is that it has a significantly larger toll bar. The Mantus roll bar bolts to ears that extend out from the flukes adding to the diameter. The downside is that it’s a BIG anchor and difficult to fit in many boats. The upside is it is less prone to plug with grass, the hole is bigger and it can just pass through, if it does plug it will do so less frequently.

But also, if you wanted to experiment with the bar on a Mantus you could just unbolt it and see how it works. Don’t like it? Bolt it back in!

Mantus also packs flat for shipping, some additional upnfront cost saving.
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Old 30-08-2019, 04:30   #20
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Re: Rocna roll bar

Mantus now has the M2, a spade-type anchor with heavy ballast and no roll bar. It is a relatively heavy anchor, similar to the Vulcan in weight, and both are significantly heavier than the equivalent Spade, based on their respective sizing guides.

We’re looking to upgrade our current S140 (30kg) anchor to an S180 (45kg and 1800 sqcm area). The equivalent M2 is 57kg and 2400 sqcm area. The equivalent Vulcan is 55kg and 2360 sqcm area.

Does Spade exaggerate their holding power with less weight and less surface area than their newer competitors? Or is it really more efficient?
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Old 30-08-2019, 04:56   #21
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Re: Rocna roll bar

For any given weight, the reliability and effectiveness of an anchor's design is determined by the way that material is distributed and shaped.

Say the aim is to produce the best possible anchor out of 10 kg of steel. The worst possible shape, I expect, is a sphere.

A 10 kg cube is a little better, though still useless. There is now some friction from the edges.

As the shapes get ever more elaborate, there is also robustness to consider. The anchor cannot have its material distributed so thinly that it is in danger of being bent or ripped off by the expected load.

The Rocna dedicates a comparatively small amount of material - the rollbar - to ensure correct orientation. It can thus afford to have more surface area in the fluke, and/or a stronger shank.

Delta-type designs must concentrate more weight in a ballasted tip, which actually makes the fluke area smaller. For a given weight, more of the Delta's material is given up to the mechanism that ensures orientation.

Chopping off a Rocna's rollbar does not improve the design. On the contrary, it results in something that is almost certainly less likely to dig in, perhaps less structurally sound, and overall less safe and effective.

I expect that anchors have now reached a point where further massive gains won't come from a human designer, but perhaps from the application of machine learning or AI. There may be as-yet-unexplored fantastic shapes that are asymmetric or simply weird to the point where they do not even look like what we consider to be an anchor. Whether they will be adopted will presumably depend on whether they're much better than the current designs.

EDIT: It also occurs to me that protein-folding recursive algorithms have things in common with the kind of CAD approach that might produce a leap in anchor design. Soon it might be possible to download a screensaver that will utilise your PCs idling horsepower to come up with an open-source superanchor
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Old 30-08-2019, 05:20   #22
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Re: Rocna roll bar

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Does Spade exaggerate their holding power with less weight and less surface area than their newer competitors? Or is it really more efficient?
Unfortunately, many anchor companies try and recommend an anchor as small as possible. Many people assume that if the manufacturer recommends a smaller anchor, the anchor must be a better and more effective design.

In reality the opposite is true with companies such as Lewmar with their Delta and Plastimo with their Kobra recommending anchors much smaller than more capable (in my view) anchors such as Mantus, Rocna and Spade.

The other factor driving these smaller than sensible recommendations is that it helps convince large boatbuilding companies such as Beneteau to use their anchor as original equipment. Boatbuilders prefer a company that will endorse small anchors, as this saves money not only on the anchor, but also importantly on associated equipment such as the windlass.

The Mantus M2 and Rocna Vulcan are new anchors and it is difficult to gauge their effectiveness. If a roll bar anchor will not fit your vessel, the steel Spade is a proven performer and is going to be tough to beat. Don’t be afraid to use Rocna or Mantus tables when choosing the size of your Spade. Even better for a cruising sailor, the philosophy of fitting the largest anchor the vessel and crew can comfortably manage is perhaps an even better sizing starting point.
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Old 30-08-2019, 06:37   #23
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Re: Rocna roll bar

I have a galvanized steel Mantus dinghy anchor from the first commercial batch sold. It has no roll bar. It generally lands right side up. When dropped in the water as a stern anchor before tying the dinghy to a dock, it fails to set about one time out of ten. In the Bahamas I can frequently see it on the bottom, and when it fails to set, it is upside down. No amount of dragging it about will make the upside down anchor re-set. It has to come up and go down a second time.

The newer stainless steel version of the Mantus dinghy anchor has a roll bar. Today, I don't see the "roll bar-less" galvanized dinghy anchor on their web site https://www.mantusmarine.com/product...inghy-anchors/ .

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Old 30-08-2019, 07:24   #24
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Re: Rocna roll bar

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So, OP, you posed a question about removing the roll bar from your Rocna. Several knowledgeable folks, sailors who have personally investigated the behavior of roll bar anchors in action, have advised that it isn't a good idea.
You disagree and dismiss their opinions. OK, your mind is made up, and you are gonna do it. Fine... we all hope that you get the results that you wanted. I just wonder why you bothered to post the question if you ain't gonna listen to the answers?Jim

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Old 30-08-2019, 13:38   #25
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Re: Rocna roll bar

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Originally Posted by noelex 77 View Post
Unfortunately, many anchor companies try and recommend an anchor as small as possible. Many people assume that if the manufacturer recommends a smaller anchor, the anchor must be a better and more effective design.

In reality the opposite is true with companies such as Lewmar with their Delta and Plastimo with their Kobra recommending anchors much smaller than more capable (in my view) anchors such as Mantus, Rocna and Spade.

The other factor driving these smaller than sensible recommendations is that it helps convince large boatbuilding companies such as Beneteau to use their anchor as original equipment. Boatbuilders prefer a company that will endorse small anchors, as this saves money not only on the anchor, but also importantly on associated equipment such as the windlass.

The Mantus M2 and Rocna Vulcan are new anchors and it is difficult to gauge their effectiveness. If a roll bar anchor will not fit your vessel, the steel Spade is a proven performer and is going to be tough to beat. Don’t be afraid to use Rocna or Mantus tables when choosing the size of your Spade. Even better for a cruising sailor, the philosophy of fitting the largest anchor the vessel and crew can comfortably manage is perhaps an even better sizing starting point.
As always: somebody who REALLY knows what he is writing about
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Old 30-08-2019, 13:55   #26
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Re: Rocna roll bar

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If you don't like my thoughts, mind your own business Your opinion means nothing.
Come on Ecos...cool it man. Jim had a good point.
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Old 30-08-2019, 14:00   #27
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Re: Rocna roll bar

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Look at the videos of anchors setting that are posted elsewhere on CF.


The "roll bar" contributes to the anchor resetting after a change in the direction of pull, particularly in some types of bottom conditions.


Difference between a 99% anchor and a 99.9% anchor
Whoa whoa whoa. It's waaaay more than a .9% difference in my experience.

The anchor setting videos are good for relative performance observations in what are pretty benign and unchallenging conditions. They don't test an anchors ability to perform day in and day out in widely varying conditions.

For example, I have anchored with my 25kg Rocna in areas with switching strong currents and subject to brief squalls of 40+ knots where the anchor's ability to reset in various substrates is extremely important.

I would no sooner cut the roller off my Rocna than I would cut the tip off.

If you think the rollbar is just marketing I suggest you look at Peter Smith's (the designer) personal website at https://www.petersmith.net.nz. He's not some corporate schmoe.

The Rocna Vulcan was designed for boats that cannot accommodate the rollbar in their anchor roller. It's significantly different, particularly in the shape of it's tip, the weight in it, and the shape of the shank. Is it as effective as the original? Probably moreso in grassy anchorages I expect. Elsewhere? Who knows.

Looking right now at my Rocna and I'm pretty sure that if I cut the rollbar off and dumped it into sand and it landed (or got flipped) on it's back that it would not function well at all, or at least not reliably.

Does the rollbar catch weeds? Absolutely. It's a weakness of the design, there's no doubt about that. But it's important to it's basic function.
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Old 30-08-2019, 14:15   #28
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Re: Rocna roll bar

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Come on Ecos...cool it man. Jim had a good point.

Quite so. And then there is the be nice rule as well.
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Old 30-08-2019, 15:24   #29
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Re: Rocna roll bar

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Come on Ecos...cool it man. Jim had a good point.

I don't think so. I have been using this anchor since 2007. I have the creds to talk about it's warts. I've not run across a 12 year, real world test yet, only my own.
I don't need any psychobabble on how I should think about my anchor.
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Old 30-08-2019, 17:55   #30
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Re: Rocna roll bar

There is the older video "Does Mantus Need a Roll Bar" where the anchor hits the bottom right side up twelve out of twelve times. Like I said, my experience with my little roll-bar-less Mantus dinghy anchor is right side up nine out of ten and once on the bottom upside down there is no chance of it righting itself.

If you have not seen the video, you might enjoy it.

Bill
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