Rocna reversal phenomenon

Any pointers on where to buy a swivel-less straightener/bent link/boomerang in the UK would be appreciated. I can only find the swivel versions in my searches.

Our Rocna mostly comes up the wrong way round too, despite a custom made roller which looks though it would make it hard for the chain to turn in it. Motoring backwards often isn't an option in our chosen spots.
 
MikeBz said:
Our Rocna mostly comes up the wrong way round too, despite a custom made roller which looks though it would make it hard for the chain to turn in it. Motoring backwards often isn't an option in our chosen spots.
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Can you say what's preventing the Rocna from righting under its own weight on the bow roller? The width of the roller?
 
NormanS said:
Any blacksmith/metalworker could make one in a few minutes, and then it's worth getting it galvanised.
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+1

Or, scale for strength, and make in stainless - same blacksmith/metalworker.

I made mine Post # 4 with a drill, angle grinder and had it galvanised. It took me more than a few minutes :( - but them I'm not a blacksmith nor metal worker). I'm making another for 8mm chain this week - but its not difficult and it does not take that long.

If you do not want to make - I'd ring Geoff at Knox Anchor - he might be interested.

Jonathan
 
Neeves said:
+1

Or, scale for strength, and make in stainless - same blacksmith/metalworker.

I made mine Post # 4 with a drill, angle grinder and had it galvanised. It took me more than a few minutes :( - but them I'm not a blacksmith nor metal worker). I'm making another for 8mm chain this week - but its not difficult and it does not take that long.

If you do not want to make - I'd ring Geoff at Knox Anchor - he might be interested.

Jonathan
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It can also be laser cut from thick plate, either stainless steel or and grade of carbon steel then galvanised.
 
biscuit said:
Having originated this thread, I will restate: the anchor ALWAYS come up reversed by 180 degrees, not 90 degrees or any angle between, which seems to negate some theories regarding chain twist. (although no doubt someone here could correct me)
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And thus the hydrodynamic explanation is the only one that fits. I know from observations this is also the case for Manson Supreme and Mantus anchors. I've watched people motoring around, trying to stow and anchor and not being able to figure out why so long as they are motoring around it will ALWAYS come up backwards.

With the new anchors, this is sailing 101.
 
Hmmm.... as I have already said (my 2nd post) it happens when the boat is moored in still water and no wind, bringing the anchor up very slowly......
 
biscuit said:
Hmmm.... as I have already said (my 2nd post) it happens when the boat is moored in still water and no wind, bringing the anchor up very slowly......
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Are you completely motionless, or are you still coasting past the anchor, having recovered the chain with the windlass at 5-7 feet per (3-4 knots)? That would be enough. 1 knot is enough. This is likely in still waters, since there is no wind to stop the boat, unless you consciously stopped it with the engine.

There are only two possibilities for it to happen all of the time. Moving forward or a twisted chain. Something must be constantly wrong and it must be something that relates to direction. Otherwise it will be random.
 
Unless you are anchoring with bicycle type chain, which cannot twist, the rest of us mere mortals have chain which has enough clearance in the links to allow twists to form quite easily, and it does.
 
NormanS said:
Unless you are anchoring with bicycle type chain, which cannot twist, the rest of us mere mortals have chain which has enough clearance in the links to allow twists to form quite easily, and it does.
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Of course it twists. The bicyle chain comment was pointlessly silly. But chain also untwists when the anchor clears the bottom. This too is obvious. If there is a twist above the roller, remove it by lowering the anchor a few feet, twisting it with either you hand or a screw driver (not while lifting, both because it is dangerous and because there is more load). Is this not quite easy? Once the chain is aligned, the anchor will come up straight unless the chain is jumping on the windlass.

You can use a swivel or turner. On the other hand, I have done the above countless times, and it is easier for me. This is not myth or internet chatter. If it does not work for you, perhaps there is some subtle difference in your gear. But I'm not playing anyone.
 
thinwater said:
Of course it twists. The bicyle chain comment was pointlessly silly. But chain also untwists when the anchor clears the bottom. This too is obvious. If there is a twist above the roller, remove it by lowering the anchor a few feet, twisting it with either you hand or a screw driver (not while lifting, both because it is dangerous and because there is more load). Is this not quite easy? Once the chain is aligned, the anchor will come up straight unless the chain is jumping on the windlass.

You can use a swivel or turner. On the other hand, I have done the above countless times, and it is easier for me. This is not myth or internet chatter. If it does not work for you, perhaps there is some subtle difference in your gear. But I'm not playing anyone.
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On my previous boat, which had a vertical stem, I had a mark on the chain to tell me that the anchor was just under the stem. At that point, I stopped heaving in, and if I could see the anchor, and if it was facing the wrong way, I did indeed rotate the chain with a "poker". It still wasn't a picnic, as the anchor weighed 140lbs.

My present boat has a raked stem, and the bow rollers are extended forward. Now I can just heave up, slowing a little just when the bent link reaches the roller, when it automatically rotates the 20kg anchor, if required, to the correct orientation. What's not to like?
 
I’m a little confused by the op. Is he saying that with anchor pulled right up to the bow roller, the Rocna is upside down and that the chain, from winch to anchor, has a twist in it? Or there is no twist in the chain, and even unscrewing the shackle and reversing it will not stop it repeating itself the next time the anchor is deployed?
If it’s the former I would suggest a bigger bow roller roller, a banana shackle, a broomstick or to experiment with technique as advised by others here.
If it’s the latter then there is something wrong with the winch, the chain is slipping off the teeth. So the chain could contain a bad section, either a poorly repaired link or corroded link. Or the winch teeth are worn or there is not enough pressure holding the chain against the teeth. Perhaps the winch and chain are of different sizes.
He’s not using a section of rope rode is he?
 
BelleSerene said:
Can you say what's preventing the Rocna from righting under its own weight on the bow roller? The width of the roller?
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In my case the roller has a central slot the width of the anchor shank - this helps to stop the anchor moving when it is stowed. Apart from that the shank is probably too tall to do a 180 in the roller.
 
On hydro-dynamism of anchors.

I confess not to have checked many anchors but it was claimed that a Mantus always deployed correctly if the yacht was moving backwards, so I tested it - and this is correct. Or for a yacht moving forwards, which is not unusual (or not impossible) it will be the wrong way round - but during deployment this really does not matter - as you will eventually reverse and it will then sell align. But this underlines - you cannot take the roll bar off!! because if you do, take the roll bar off, and it arrives back to front and upside down - a Mantus will never, ever, turn the right way up.

I was then intrigued and hung it in air, from a balcony at home, so it was hanging about 3m vertically (or 3m of chain). I hung it in the breeze - and it self aligned in the breeze (which I found quite extraordinary - even if a totally useless piece of information).

But - anchors, or at least one, will self align at the slightest chance - and some may self align with the opposite effect.

But if you have a Mantus and retrieve when moving forward, which would be quite normal - it will arrive at the bow roller, or at least break free of the water, back to front - every time. I'm not sure how this works if your anchor is full of mud :( another common occurrence.

Jonathan
 
Bouba said:
I’m a little confused by the op. Is he saying that with anchor pulled right up to the bow roller, the Rocna is upside down and that the chain, from winch to anchor, has a twist in it? Or there is no twist in the chain, and even unscrewing the shackle and reversing it will not stop it repeating itself the next time the anchor is deployed?
If it’s the former I would suggest a bigger bow roller roller, a banana shackle, a broomstick or to experiment with technique as advised by others here.
If it’s the latter then there is something wrong with the winch, the chain is slipping off the teeth. So the chain could contain a bad section, either a poorly repaired link or corroded link. Or the winch teeth are worn or there is not enough pressure holding the chain against the teeth. Perhaps the winch and chain are of different sizes.
He’s not using a section of rope rode is he?
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In my case it is the latter. There is absolutely nothing wrong with my chain or windlass. Between anchor and windlass is the bow roller, which would seem to prevent any rotation of the chain, but it happens often. The photo shows my original roller, the starboard one being the one over which the chain runs. I would imagine that in most circumstances this would hold the chain in alignment. However, just in case this was not true I had new rollers made with tighter clearances. It made no difference. Photo shows the original roller.
 
After 30 years that good but lots of people think stainless steel does not rust at all. This shows that it can particularly where its welded.
 
Rogershaw said:
After 30 years that good but lots of people think stainless steel does not rust at all. This shows that it can particularly where its welded.
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We have had many discussions about this in the past. Stainless steel for welding should be the low carbon grades, 304L, 316L, etc. For really critical items 347 is best, as this is low carbon and contains niobium, a preferential carbide-forming metal. The electrodes should be selected carefully to give low carbon content, maybe with slightly raised chromium levels. Again, 347 is a good choice, especially in the 19-9 grade.
 
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