Rocna reversal phenomenon

[Neeves]

None of this has anything to do with the anchor type, its not special to Rocna. We were in The Harbour 6 months ago and a crewed charter boat went past with a CQR (probably a copy) inverted on the bow roller. We were doing something critical and going the other way - otherwise I'd have taken a photograph. It happened, before Norman introduced the Forum to his bent link, with our Excel - but no more.

Interestingly Rex Francis from Anchor Right said the same thing when he saw my Boomerang as has been said - that anchors are designed to self right. He also sells bow rollers and replacement rollers - so he is in the right place and ought to know what he is doing. He then reviewed his comments in view of the comments he received from customers - copied the design and sells it. He would not have them in his portfolio if it was an easy issue to overcome some other way. It is a common problem.

But even if an anchor does self right on the bow roller - when you get up in size - having a heavy lump of steel self righting on your bow roller is not a good look - aligning it prior is so much more gentle (and will not damage anything on the bow roller) and needs no human intervention.

Jonathan

 

[thinwater]

Because the groove makes it stay upside down?! Seriously, not trying to be thick here - trust me, I do it naturally...

I respect a question worded like that! Often times what seems like a dumb question is just a request for a plainly worded explanation. I also share the same basic question.

I've always felt that that the groove should match the chain, not the anchor shank. My reasoning is that if the anchor shank fits deeply in the groove (or a boomerang) it can hang-up, inhibiting natural righting. On the other hand, if the groove matches the chain, the chain just might stay straight, or at least stay straight after it has been aligned. So long as there is a V to the roller, stowing the anchor just seemed to be a matter of tension and it the groove didn't need to fit the shank.

This may be one of those things that leads people to different conclusions about what is normal behavior; if you have always had a groove that fits X, you expect behavior Y. Rather like how people that anchor with chain in 10 meters of water in 25-30 knots have a different understanding of catenary than those who anchor in 2 meters of water through 50-knot squalls.

 

[Neeves]

Its not quite that simple to choose the roller:

You might have 8mm or 10mm chain, both could be the 'right' size for the same sized yacht in G30 which might be replaced with G70 6mm. The yacht might have been commissioned with a beefy shanked CQR copy, or a Vulcan, Spade or Bruce with a profiled shank. A new anchor might be bought and following current trends - overly large (which means it will have larger/thicker shank). If you match the rebate in the roller to match one of these variables - it will not match any of the others. You could buy a new roller that has a better fit - Bent Link still seems simpler.

Our roller is a simple wide shouldered slot, a very broad and flat 'V'. I have thought of a rebated 'inverted T' to match the chain - but as soon as you retrieve at an angle the chain would pull/slide out of the slot (or it would on our roller) and then might relocate with a 1/4 twist (or more) - negating the whole function of the slot. I fitted cheeks to accomodate retrieval off centre. I know you should retrieve in a straight line - not always possible single handed.

I don't think there is one 'right' answer - there never is (especially if the question has the word anchor in it somewhere). Its a question of eliciting all the options and choosing what is best for you - and best might involve compromises that seem illogical to others (such as you do not want to make, cannot source a bent link and think it the wrong option anyway!)

Jonathan

 

[thinwater]

I don't think there is one 'right' answer - there never is (especially if the question has the word anchor in it somewhere). Its a question of eliciting all the options and choosing what is best for you - and best might involve compromises that seem illogical to others (such as you do not want to make, cannot source a bent link and think it the wrong option anyway!)

Jonathan

Case in point. I was going to try a bent link, but there simply is not room between the chain roller and the chain lock or the chain lock and the windlass without moving something that would be difficult to move. I have tired them on other boats and it seems like an obvious, effective answer if it fits... except for one boat where the roller channel was so narrow the link jammed perfectly. It was several hours getting it out. It's always something.

 

[Neeves]

Bent Links don't need to be as long as 'mine', I made a prototype that was half the length - it still works (and is currently used as paper weight), but I have maybe 2m between bow roller and windlass - so length does not matter to us and my longer version is better. They can also be made from thicker, or thinner plate - you might need to make the link wider if the plate is thinner. We have been using a number of links between link and anchor - these can be reduced - the longer Boomerang and more links simply all allow more time for an anchor being retrieved by a fast moving windlass (from memory our Maxwell operates at 2m/sec) to settle down from an inversion before it reaches the bow roller.

I worked on the basis the plate should be the same, approximate, thickness as the chain link diameter and that no other dimension, round the shackle hole, should (again) not be smaller than diameter. With a 800 MPa steel its then grossly over engineered for a G30 chain. But I preferred that when you are suggesting people make their own - as it increases the safety factor. Theoretically the Boomerang could be much smaller - but there is then the danger of someone, literally, cutting corners (or say making from mild steel).

Anchor Right tested an 8mm version and it failed at 9t vs specification of 3t for a 8mm G30 chain (but commonly 4t UTS) and Grade B 3/8th" shackle (which would fit 8mm chain and many appropriate anchors) with a UTS of 10t/12t.

I have been involved in a number of 'installations' of Boomerangs and certainly they simply will not fit on some yachts as the windlass is so far forward. The answer to the inverted anchor then needs to lie in another direction (and some ideas have been aired on this thread). Commonly simply reducing the number of links between Boomerang and anchor does suffice. For my G80 chain, and a subsequent G100 chain, the slot for the shackle had to be modified to accept an Omega link (and plate thickness had to be compatible with the Omega mouth) but these are exceptional cases - and actually quite easily overcome.

Lateral thinking helps

Jonathan