Choice of material for anchor roller

[chubby]

What is there to choose between the hard black rubber or the hard white plastic ones in terms of durability and performance? I want to replace old white plastic rollers and can either find the nearest match ready made or find somewhere to machine one, also some have a groove and others a smooth curve, presumably the anchor sits in the groove?

 

[NormanS]

I made one using several layers of some kind of 10mm resin sheet which happened to be lying under the bench. Cut at different diameters, and glued together with epoxy. Not entirely trusting the epoxy, I fitted bolts to hold it all together as well. The groove in the one for chain may help to stop the chain from rotating and twisting. I believe that "Delrin", a hard wearing resin product is sometimes used.

 

[vyv_cox]

The ones that came on my boat were nylon. They were perfectly OK but the shape was concave, allowing the anchor to slide from side to side on tacks. I replaced them with acetal, of which Delrin is a trade name.

 

[AMOREST]

HDPE. I’ve made a few rollers for neighbouring yachts fitting ROCNAS. (Don’t start ?)

It allows the right diameter in the groove to hold the shank snug. (15Kg 90mm) etc.
And the slot guides the chain pretty well stopping rotation.

On one you can see how the shank can be off set - to protect the forestay assembly.

Nylon can absorb water over time.
These have been successful so far.
Cheers
A.

 

[Neeves]

If the slot in the roller is sufficiently large to accept the anchor shank then if the anchor comes up inverted and the shank is in the slot it may not self right. If it does self right the action will chew up the roller.



And/or it may self right at the roller and as it rotates to self right it might belt something that is less strong than the anchor - furler drum, gel coat.
Ideally the slot wants to be marginally bigger than the chain link, and then every alternate links is held in the slot (and forces the chain to untwist (using increased torque and gravity). Anchors around 15kg in weight will have a 16mm shank and held on a 8mm chain (there are exceptions) - so there is a biggish difference.

As mentioned - unslotteds rollers allow the chain to swing/slide from side to side and the chain can abrade the bow roller cheeks and or the cheeks will wear the gal more quickly.

If you can introduce a slot -the slot has a lot of advantages.

Materials for the roller - see above.

Jonathan

 

[NormanS]

If the slot in the roller is sufficiently large to accept the anchor shank then if the anchor comes up inverted and the shank is in the slot it may not self right. If it does self right the action will chew up the roller.

View attachment 128558

And/or it may self right at the roller and as it rotates to self right it might belt something that is less strong than the anchor - furler drum, gel coat.
Ideally the slot wants to be marginally bigger than the chain link, and then every alternate links is held in the slot (and forces the chain to untwist (using increased torque and gravity). Anchors around 15kg in weight will have a 16mm shank and held on a 8mm chain (there are exceptions) - so there is a biggish difference.

As mentioned - unslotteds rollers allow the chain to swing/slide from side to side and the chain can abrade the bow roller cheeks and or the cheeks will wear the gal more quickly.

If you can introduce a slot -the slot has a lot of advantages.

Materials for the roller - see above.

Jonathan

Fred Drift here. I don't know what kind of boat that is, but is that "fairlead" in your pic specially designed to cut whatever line is put in it, at some particular tension, or is that just left to chance? Also, although it's difficult to get a true sense of scale, that anchor looks like something out of a Christmas cracker. ?

 

[Neeves]

Fred Drift here. I don't know what kind of boat that is, but is that "fairlead" in your pic specially designed to cut whatever line is put in it, at some particular tension, or is that just left to chance? Also, although it's difficult to get a true sense of scale, that anchor looks like something out of a Christmas cracker. ?

She is HMAS Dugong, built 2001, and 65' long. She is used as a dive support vessel (as are her 2 sister ships). The anchor is used, I've seen Dugong anchored quite often. She is locally built, from aluminium. She is based at the dive school, HMAS Penguin in Sydney but spends some time at their annexe on Pittwater (which is where the picture was taken). When she was commissioned the anchor choice would have been CQR, Bruce or Danforth. The fact that the anchor 'looks' original suggests - it does what is required.

I cannot comment on the bow arrangement, the fairleads, nor the anchor retrieval practices. I can confirm she has very large, or at least noisy, Diesel engine(s).

Take care, stay safe.

Jonathan

 

[vyv_cox]

If the slot in the roller is sufficiently large to accept the anchor shank then if the anchor comes up inverted and the shank is in the slot it may not self right. If it does self right the action will chew up the roller.

View attachment 128558

And/or it may self right at the roller and as it rotates to self right it might belt something that is less strong than the anchor - furler drum, gel coat.
Ideally the slot wants to be marginally bigger than the chain link, and then every alternate links is held in the slot (and forces the chain to untwist (using increased torque and gravity). Anchors around 15kg in weight will have a 16mm shank and held on a 8mm chain (there are exceptions) - so there is a biggish difference.

As mentioned - unslotteds rollers allow the chain to swing/slide from side to side and the chain can abrade the bow roller cheeks and or the cheeks will wear the gal more quickly.

If you can introduce a slot -the slot has a lot of advantages.

Materials for the roller - see above.

Jonathan

I thought the same but unfortunately the reality is different. My roller groove was sized for the Rocna shank, which fits well, holding the anchor centrally when tacking. But the chain goes wherever it wants, sometimes with links in the groove but often jumping out and forming an X across it.

The hauling speed of my Maxwell (one of the fastest on the market) is such that the anchor rotates as it rises, presumably due to its shape. If I attach the chain with a shackle the twisting is so bad that the anchor will not come aboard. With a swivel no twisting of the chain occurs between roller and windlass.

 

[Neeves]

I have seen double notched rollers. A thin notch for the vertical links and a wider notch for the horizontal links. The over all depth of the 2 notches should be sufficient to stop Vyv's problem with the links jumping out and the small notch will still be too small for the anchor shank and the wide notch not an issue. The roller needs to be quite beefy to accomodate the 2 notches.

In terms of making your own - a double notch will not be more difficult than a single notch.

Vyv is right about the speed of retrieval of a Maxwell windlass - quite extraordinary.

Jonathan