Rocna reversal phenomenon

I'm amazed that so many have the same issue.

I do see slotted rollers (for bow rollers). The slot ensures that each alternate link falls into the slot - or that is the theory. I would have thought if you had a lot of twist in your chain that modern windlass are so fast - the links might jump. I've only ever seen these slotted rollers on older yachts and the rollers are bronze (?) and must hammer the galvanising. It would not be difficult to machine a polymer roller with a slot - instead of a wedge.

The Oscalluti bent links are a poor design - the swivel is a weak point (as with any swivel) and they are prone to locking up - Viv had a photo some time ago where his locked up at right angles to his shank - perfectly designed to make any anchor drag

Anchor Right make Flip Links, a direct copy of the Boomerang. I believe there are, similar design, available in America (where I have heard them called bananas). They are easy to make, all you need is the steel, a decent drill and an angle grinder. If you speak to a galvaniser nicely - they would galvanise for you. I made mine, I have a few as the design developed, Norman and Roger made theirs - its not difficult - and given the number of people with the exact same issue - a small commercial opportunity for someone in the UK (Knox Anchor?). Norman and Roger both used rod, which thenythen bent - not sure how you make a bend?? they then welded attachment points (and I agree with Norman about using a fork direct onto a shank (very observant!).

However I suspect some of the problem is that the anchors are not connected correctly. The first thing to check - have you induced any twists into the chain or attached the anchor to the wrong link (every link is at 90 degrees to the links on either side, use the 'wrong' link and your anchor will ALWAYS come up sideways).

Jonathan
 
My interpretation is that there is two grooves. The narrow deep groove for the vertical links and a wider shallow groove for the horizontal links. This should help keep the chain running true
 
Sorry Bouba, I did not understand your first post '2 grooves' - I think you are correct its a 'sort of' rebated 'T' a deep narrow groove and a wide groove superimposed on each other.

If you do not have a new windlass you might be surprised how quick they are - far too quick to allow any twists to fall out - the twists need to go somewhere - and I suspect they would jump the grooves. Better to stop the windlass when the anchor is hanging about 2 metres below the bow roller and let any twists fall our with torque and gravity. But that needs patience - sometimes not available at the precise moment :(. But even with the grooves if you have attached the anchor to the wrong link, one at 90 degrees to the right link - the anchor will ALWAYS arrive sideways.

If your anchor is correctly attached and you cut off the first link, because with time it corrodes, your anchor will now come to the bow roller sideways. If you cut off 3 links, or any number of odd links, it will come up sideways - easily done (and easily remedied).

Jonathan
 
I wouldn't worry. A Rocna backwards is an ancor which sounds so much more useful. Adding an ananab should help.
 
My (nylon?) bow roller has a groove for the vertical links, but the chain still occasionally rotates. I wouldn't cut off the end link to get the anchor facing the right way. It's surely easier just to lift the chain off the gypsy, and put it back on to suit the anchor.
 
NormanS said:
My (nylon?) bow roller has a groove for the vertical links, but the chain still occasionally rotates. I wouldn't cut off the end link to get the anchor facing the right way. It's surely easier just to lift the chain off the gypsy, and put it back on to suit the anchor.
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Possibly, or probably.

When I installed our new chain I fed it though the gypsy. As far as I am aware the chain in the chain locker is untwisted. I'd like to keep it that way. I also made sure when I attached the anchor that it was aligned correctly. So, for us, the situation does not arise. its impossible for twists to 'get through the gypsy'.

I have to assume everyone else has untwisted chain in their locker, though that's possibly unrealistic, and I would not want to introduce twists. If I was helping someone with this very issue - I'd arrive with bolt croppers and I'd hope they did not have 12mm G70 chain :(. It would then be easier, for me, to simply chop one link off but I don't know anyone with 12mm chain (nor 6mm) and chopping off one 8mm or 10mm link is not difficult. Never having done it I don't know how easy/difficult it is to lift the chain off the gypsy and put it back, correctly.

Either option will be much easier with 6mm rather than 12mm chain!

But then I'm constantly swapping anchors - so my option is second nature.

I think this query came up previously - and I have not altered my practice!

Jonathan
 
Well, bully for you. It doesn't for me. The post is self-evident( I thought). Naturally I have tried such "simple solutions" such as untwisting the chain, winching up and down, trying it on the next link, etc to no avail.
once, in the past, the anchor has "uncapsized" itself as it came over the roller, and taken a chunk of G.R.P. adjacent to the bow fitting with it! As stated, the deep rectangular section of the shank of the Rocna makes this possible.
I wanted, and hope I have now found (thanks guys) a solution that will stop this happening, particularly with a relatively inexperienced crew member working the windlass.
 
NormanS said:
Well, I'm sure it works the same way, but for obvious reasons, I don't like his fork end direct on to the anchor, and I see no reason to fit a swivel. The basic idea is similar. When the bend in the link reaches the bow roller, it automatically rotates the anchor into the correct orientation.

It helps if the bow roller is extended forward, so that the rotating anchor doesn't ding the bow. It also requires sufficient length between the windlass gypsy and the end of the anchor, to accommodate the link.
Click to expand...

Yes the Fork on the anchor could/should be replaced with a short length of chain or shackle.

Just been having a PM conversation with Neeves about that.
 
Neeves said:
Norman and Roger both used rod, which they then bent - not sure how you make a bend?? they then welded attachment points (and I agree with Norman about using a fork direct onto a shank (very observant!).


Jonathan
Click to expand...


To bend 25 mm solid steel bar I used an oxy acetylene cutting torch and 2 25mm solid bars clamped vertically in a large vice. Heated until red hot the bent using a long sched 40 tube over the end of the solid bar.

A LPG gas torch may also do the job.

I will be modifying the connection to my anchors in due cause as discussed.


This is my bow roller arrangement with just a single depth wide groove to take the chain.

35696532360_9b08fa232e_b.jpg


View from the top

35246297674_e96f89551e_b.jpg


Yes I know I have 2 swivels
 
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Neeves said:
I do see slotted rollers (for bow rollers). The slot ensures that each alternate link falls into the slot - or that is the theory. I would have thought if you had a lot of twist in your chain that modern windlass are so fast - the links might jump. I've only ever seen these slotted rollers on older yachts and the rollers are bronze (?) and must hammer the galvanising. It would not be difficult to machine a polymer roller with a slot - instead of a wedge.
Click to expand...

Plastic rollers with a slot are very common here.
 
Rogershaw said:
To bend 25 mm solid steel bar I used an oxy acetylene cutting torch and 2 25mm solid bars clamped vertically in a large vice. Heated until red hot the bent using a long sched 40 tube over the end of the solid bar.

A LPG gas torch may also do the job.



I will be modifying the connection to my anchors in due cause as discussed.
Click to expand...

Sounds sufficiently robust!

It merits note

Anchor makers have gone out of their way to produce thin shanks, because thicker shanks (think the 'I' section of the CQR) reduce the ability of the anchor to set deeply. This is why Peter Smith went to Bis 80 - its a high tensile steel and allows a thinner shank. Knox have gone further with strength, I think they use 900 Mpa steel - though I'm not sure the shanks are any thinner (than the equivalent Rocna). But though the shanks are thin I have not heard of anyone with a 800 MPa shank that has bent (so Peter Smith got it right) - but I stand to be corrected. There has been lots of research on the effects of shank thickness - its a real and accepted problem (not something Peter Smith dreamt up as a marketing gimmick) and if you check oil rig anchors they have gone for a ladder construction (2 shanks joined by 'rungs').

A Flip Link, Boomerang, Banana that is thicker than the chain will also act as an obstruction to setting. At the back of my mind I believe it is possible to source HT steel rod and this could then be thinner, as thin (or thinner) as the chain. Again this is not something I have dreamt up there is plenty of research on the resistance chain contributes to the setting of anchors - and thinner chain (upto 1000 MPa, equivalent to G100) is quite accepted - and used - despite others saying otherwise).

Just an idea :)

I went with steel plate, because I wanted my device easy to make (angle grinder and drill) - by chance (I take no credit) an 8mm steel plate of an 800 Mpa steel is thinner but can be (much) stronger than the chain (assuming 8mm chain).

A bent HT round rod would be 'better' than my plate (because it is rounded) but It would need welded ends, not something you can do in you kitchen - or not if you are married.

But, as usual, I might be being a bit pedantic :)

Jonathan
 
biscuit said:
. Naturally I have tried such "simple solutions" such as untwisting the chain, winching up and down, trying it on the next link, etc to no avail..
Click to expand...
I've untwisted the chain between windlass and bow roller then watched it like a hawk before and still somehow the chain can retwist itself invisibly . Luckily with my bow roller it's quite easy to give the remote a few stabs so the anchor spins round again as it comes over.
 
Roger - That's a decent bow roller - I simply do not understand why boat builders have economised on bow rollers. On new yachts a double bow roller is a real exception and any bow roller on a recent yacht that is robust is unusual. On a smaller yacht a single bow roller is probably sensible as you can deploy a second anchor by hand - bur once you get to 20kgs and then add its chain - 2 rollers seems more realistic.

I love the chain locks - and am envious.

But I cringe at that second, stainless, swivel - it looks the sort that are on Vyv's website notorious for failing and is in contradiction to the size (and strength) of the galvanised swivel. I might suggest simply replacing the stainless swivel for a decent Grade B shackle (Crosby G209A) - unless there is some other reason to use the swivel??

Jonathan
 
My chain is 10mm. My bent link is made of 12.5mm round bar. I doubt if the difference in pulling it through the mud, compared to pulling the length of chain it replaces, could be measured. It's holding us right now :D
 
GHA said:
I've untwisted the chain between windlass and bow roller then watched it like a hawk before and still somehow the chain can retwist itself invisibly . Luckily with my bow roller it's quite easy to give the remote a few stabs so the anchor spins round again as it comes over.
Click to expand...

I can second that. Even with my slotted bow roller it still twists itself again even after letting the whole lot out in deep water to untwist it. :confused:

Rihard
 
RichardS said:
I can second that. Even with my slotted bow roller it still twists itself again even after letting the whole lot out in deep water to untwist it. :confused:

Rihard
Click to expand...
Have you gone over every link to see if there are any bent, corroded or stuck
 
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