Mixing metals at the mast head

[contessaman]

Hi folks,

Following on from some of my earlier posts regarding metal sheaves at the mast head. Let's just say I'm hell bent on replacing wire halyards and metal sheaves with new wire halyards and new metal sheaves.

I've determined I can't get new metal sheaves so I'm having some machined. Selden Originals were aluminium/alloy of some kind and we're mounted on stainless bolts. I'd say they were prone to seizing a bit as the alloy does it's well known white powder stuff and gripped the stainless bolts.

If I could afford bronze block to make new sheaves I would but price is prohibitive.

Option one is to use aluminium again and get the finished article anodised .

Option two , what about yellow brass? My gut feeling is it will react less with the stainless bolt it spins on? Perhaps it will be softer than aluminium though and wear excessively where the stainless wires run on it?

When I look at my Edison steering , that's stainless wire running on some kind of yellow metal pulley and has managed 40 odd years without trouble. But maybe the pulley is bronze ....

Thoughts please ?

Other option is stainless but where to get stainless block to machine them from and again that could cost a ridiculous amount .

Thanks

 

[Sandy]

Have you considered a non-metal sheaves? If not why not?

 

[thinwater]

Switch to Dyneema halyards. I'm pretty conservative on rigging, but I can't think of an argument in favor of wire, and I have made this conversion before. When you are changing sheaves is the right time. I don't think anyone is installing wire on new boats. Changing to a Dyneema halyard also reduces corrosion by reducing the conductive path to the sheave. No more cable halyards!

I'm betting you can find the sheaves if you broaden your search.
Sheave Sizing — Zephyrwerks, The Sheave Factory

 

[Keith 66]

If your mast is Wooden make them from bronze if you wish, If you have an alloy mast the bronze will react violently with the Alloy as they are far apart on the galvanic scale. I would get some tufnol sheaves or make them from Tufnol or Delrin.

 

[penfold]

Aluminium with nylon top hats to avoid corrosion with the stainless axle; anodising would be nice, but with wire rope running over it the anodising won't last long anyway. If the existing pulley is only worn/corroded at the bearing surface have it bored out and top hats fitted for maximum stinginess.

 

[dunedin]

Hi folks,

Following on from some of my earlier posts regarding metal sheaves at the mast head. Let's just say I'm hell bent on replacing wire halyards and metal sheaves with new wire halyards and new metal sheaves.

Well it takes all sorts, and you clearly must have some reasons - but as you have found, this makes things much more difficult these day, and generally results in missing all the benefits of moving to modern rope halyards - which with dyneema cores, have all the non stretch properties of wire, without most of the drawbacks.
But masochsim is a hobby for some

 

[doug748]

Hi folks,

Following on from some of my earlier posts regarding metal sheaves at the mast head. Let's just say I'm hell bent on replacing wire halyards and metal sheaves with new wire halyards and new metal sheaves.

Use a suitable alloy and you should be ok:

What Aluminum Alloys Are Used in Marine Applications

Some of mine have a pressed in stainless bush but I would not try this if there is any lateral room in the box for it to become detached.

As Keith66 has suggested, I might try plastic but the choice is yours. You might get what you need from an old mast, riggers often have a pile of broken stuff - I am in an area with lots, but you do need to front up in person when begging.

.

 

[geem]

Converted mine to dyneema 10 years ago. There is no merit in keeping wire.

 

[Norman_E]

Aluminium with nylon top hats to avoid corrosion with the stainless axle; anodising would be nice, but with wire rope running over it the anodising won't last long anyway. If the existing pulley is only worn/corroded at the bearing surface have it bored out and top hats fitted for maximum stinginess.

Good solution, though nylon needs to be a slightly sloppy fit on the stainless shaft as it expands when wet. Polyurethane or acetal are IMHO better materials to use for bearings where low speeds but high forces are involved, such as masthead sheaves. Delrin is a commonly available and is suitable, it is a type of acetal homopolymer.

 

[vyv_cox]

I sleeved my mast foot aluminium sheaves with nylon many years ago. As has been said, nylon is not the optimum material but given enough clearance it has proved to be quite OK.

 

[BabaYaga]

Thoughts please ?

Could you not get hold of second hand alu sheaves in good condition?
On my own 40+ yo Seldén mast I have replaced all the original alu sheaves with composite ones – not because they were really worn (only rope running rigging), but because they tend to get sticky on their stainless shafts due of corrosion, as mentioned up thread.

 

[andsarkit]

Good solution, though nylon needs to be a slightly sloppy fit on the stainless shaft as it expands when wet. Polyurethane or acetal are IMHO better materials to use for bearings where low speeds but high forces are involved, such as masthead sheaves. Delrin is a commonly available and is suitable, it is a type of acetal homopolymer.

You can probably find an off the shelf bearing here: IGUS have a huge range of sizes and materials.

 

[Halo]

Best bet is to sleeve with acetal IMHO

 

[Tranona]

The OP did say that he has explained why he wants to keep wire halyards in earlier threads - perhaps he should have repeated his reasons then the replies might have focused on the actual questions which is first whether anodising aluminium would be helpful or is there an alternative metal. The alternatives of dyneema and/or acetal sheaves are just not the answer for him.

 

[robtoujours]

Plain bearing Tufnol sheaves for Wire rope available here:

HYE Spare Sheaves for Wire Rope from 4,45 € buy | SVB

If not wire then normal replacement sheaves are available from Barton, Selden etc in anodised aluminium etc

 

[contessaman]

The OP did say that he has explained why he wants to keep wire halyards in earlier threads - perhaps he should have repeated his reasons then the replies might have focused on the actual questions which is first whether anodising aluminium would be helpful or is there an alternative metal. The alternatives of dyneema and/or acetal sheaves are just not the answer for him.

im glad somebody said it !

im NOT switching to rope because I don’t want to. I sail almost always on my own and the wire halyards on captive winches work very well for me. When hoisting the sail I don’t have masses of rope to gather up. One hand for me and one for the winch that’s it. When dropping the sail rather than letting go a clutch and dumping the entire sail I can ease the brake on the drum to the extent that the sail does not quite Drop under its own weight , but I can pull it down easily And I can flake it as i go. But more than any of this, the thing I like the best is that feeling of the weight Of the sail I get when hoisting . If I switch to rope , change my winches for expensive self tailing Ones like I had on my previous boat , I can hoist away with a powerful geared winch , and when the sail decides to jam on its way up , by the time ive realised and winched against the jam the damned thing is stuck and neither wants to go up or down. Not a problem I’ve ever had with the wire and captive winches. If a system works beautifully for me , over thousands of miles of sailing I’m not going to change it for the sake of it.


so back to the question in hand , it sounds like yellow metal is a no no Then. The original Selden alloy ones appear to bushed in something but this is metal although I’ve no idea what . I’m afraid they are in awful condition they are chipped and corroded hence wanting to replace them. I can forgive them that as they are 40 years old. I’d be happy if their replacements give good service for half that time, I just want to do the best possible job I can of it and hence asking the question of what material to use.

to those that have suggested Tufnoil or composite sheaves, that’s what I can buy off the shelf anyway and selden recommend against it for wire halyards as they will wear through.

i can get replacements made with an acetal or nylon bush but could this crack under load ? Probably the greatest load on it is me if I go up the mast… although being on my own I don’t use the halyard to hoist me . I’ve got a 4:1 block and tackle with a certified climbing rope , I hoist that up to the masthead on the Halyard then pull myself up on the block and tackle . So it’s only my static weight I guess?

 

[DavidMcMullan]

If going to the expense of getting them machined, could you get stainless steel sheeves?