What causes anchor chain to turn ?

[OldBawley]

If I lower the anchor say 3 meter, the chain twists already as a corkscrew. It turns the anchor with it. Turning it strait with hand power is to no use, it simply returns to a twisted form.
The twisting has to do with wear, simply because the chain was strait for some years. Only recently it started twisting. I know, the solution is simple, buy new.
As mentioned in my former post, some new chains twist also.
I will make a new bow roller, the fact that the chain twists in two !!!!! opposite ways on each side of the roller is inexplicable.
The answer for the twisting is known by the manufacturers, and they do not read this forum.

 

[SHUG]

So------this is still one of Life's Great Mysteries.
If its not the anchor and not the windlass then it could be the bow roller. If the chain is biased to one side or the other this could induce a twist in the chain as it passes through....but what do I know, I'm making this up as I go along!!!!!!!!

 

[RAI]

If the links were of perfect circular cross section then they would meet at a point with no bias to twist left or right. But under load, this point would Brinell and the mutual stress point could well develop an asymmetry leading to a slight twist in each link pair. Hence old well used chain could develop a preferred direction of twist.

Since the gipsy prevents the twist passing over it, it would have to reverse the accumulated twist. The bow roller provides a suitable point for the reversal.

I'm guessing.

 

[binch]

cable twisting

I've never had this problem. Use only best cable., fit good quality swivels at anchor and at bitter end.
Now that Simpson-Lawrence has packed up, I have got chain from a man in Birmingham, who once made S-L chain. He also made hand-forged swivels to order.
Don't buy important fittings from chandlers who sell feathers on sticks for dinghy sailors.

 

[SHUG]

If the links were of perfect circular cross section then they would meet at a point with no bias to twist left or right. But under load, this point would Brinell and the mutual stress point could well develop an asymmetry leading to a slight twist in each link pair. Hence old well used chain could develop a preferred direction of twist.

Since the gipsy prevents the twist passing over it, it would have to reverse the accumulated twist. The bow roller provides a suitable point for the reversal.

I'm guessing.

I think you are beginning to make sense!!!!
The contact point between the links when new is inherently instable as its almost a point contact, so that there can easily be a small bias one way or the other which then influences the next link and so on.. As the chain wears, this bias becomes more established and......TWIST!

 

[penfold]

I have seen bow rollers with grooves made to handle only chain, rather like a gypsy only with no meshing teeth. Perhaps that would delay or prevent the bias wear and thus the twisting?

Depending on the diameter of your bow roller Oldbawley there may be enough 'meat' on it to have the worn surface turned off rather than obtain an entirely new roller.

 

[OldBawley]

I am afraid the given answers are to complicated for me to understand. Think Mr Rai and Shug are going in the right direction. Also the more rust, the stronger the twist. It is going fast now, once the galva is gone, in this volcanic area ( Poros Methana Greece ) and with non stop strong winds. The chain is in the water all the time, working and grinding 24/24h.
To Mr Penfold, I do not think a grooved bow roller is a good idea. A half circular roller is better for the sometimes big sideways forces put on the roller by the chain. Making a new roller is no problem, I have a model making lathe on board, the dimensions just fit.

 

[penfold]

A groove won't make much difference to the forces put into the fairlead/bowroller structure, that's down to how your boat sits to the anchor and how much windage she has; does she shear about a lot?

If you have a lathe and steel to spare you could make one to try it out; the groove should be deep enough to allow the chain to wrap around, so about 1/3 the width of the link(exact depth depends on the radius of the roller) and the groove width perhaps double the gauge of the chain.

 

[OldBawley]

Shearing is not the problem. The boat sits as a rock in the water. Low windage, long deep keel, 7 tons ( Empty ) for 28 feet, and the anchor chain snubber comes in at the tip of the bowsprit, so reducing shearing and pitching at anchor. More modern yachts anchor often to close, not realising we do not move as they are.
Some extreme loads have been on the bow roller and its fixing some weeks ago. Anchored on the lee shore of the Poros lake. A squall hits us, we have no instruments, think 7 Bf, it is time to go to the other side. I winch the 50 meters of chain in, ( Manual ) Swimbo is at the helm and try s to steer in the good direction. Wind increases, communication is difficult, hand signs, dark of course. The boat passes the anchor at high speed at 90 degrees. It is at that moment that huge loads come on to that roller.
I will give the grooved roller a try. Made one out of olive wood for the stern anchor. Now 10 years and good as new. The Imam of the community where we moored saw me and my toy lathe, came back one hour later with a fine dry branch of an olive tree and of an fig tree. I “Had” to make a roll for his boat to, and some pump parts out of the fig wood. He said fig was the best for under water parts. He always found new jobs for me, the last one was a wooden oil filler plug for his chainsaw.
We became good friends, he paid with fresh eggs.

 

[penfold]

Excellent! Wood is nature's own composite after all, and slow growing woods like fig and olive are tough and very hard wearing; not quite in the league of lignum vitae or ebony but durable.

 

[pampas]

for Penfold

Further to my post. I have a groved bow roller and a horizontal gypsy, bow roller to gypsy chain is straight ie no twist. but the chain gets twisted in the locker,the last 3ft ie. the bitter end. 90% of the time there is always a fair weight of chain sitting on the end but somehow it gets mangles up and takes a fair while to un-twist.
Must be Gremlins at work