seized mast sheeves

[pmorris]

Has anyone got any tips on how to free my mast sheeves.
I'ved tried plusgas and hot water with little satisfaction.
They are aluminium on a press in stainless bush, so I can't dismantle them.

Thanks in advance Paul.

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[Hardley]

The normal fitting is held to the mast by two pop rivets, which you drill out, you can then remove the complete fitting and take it to your workshop. But tie up haliyards first, don't want to loose them down the mast.
You should then be able to knock out the centre pin that holds the shreeve, they are usually worn and need replacing.
Hope this helps.

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[AndrewB]

Once again stainless steel and aluminium in combination: the boat manufacturers sure recipe for built-in obsolescence. It's high time we punters boycotted fittings like this.

The trick is to dissolve the aluminium oxide that has formed between them. It occupies a larger volume than the aluminium, and so grips tightly. A mild acid, e.g. vinegar is best, I've even found alternate dosings of vinegar and Coca Cola occasionally works. Others here have sworn by careful application of a blow-torch.

But you'll probably need brute force to crack them apart. A rope Spanish windlass might work if you get access right round the sheave. Even a plumber's chain wrench - it will mark the surface of the sheeve but that can be filed and sanded smooth after. A screw tapped into the side of the sheeve could be used to provide a purchase, cut off flush afterwards.

The danger with brute force is that instead of turning the sheeve on the bush, you turn the bush in its mast fitting (assuming the bush is pressed through the mast). Or, if the sheeve is weakened by electrolysis, that it cracks. If either happens then you'll have no option but to hacksaw the whole fitting out and replace, taking great care not to damage the mast.

Incidentally, once this has happened, it will happen again fairly quickly, so either keep the sheeve in use or replace.

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[chas]

I cleared one with lots of WD40 and a "boa constrictor" (I think they are called) - shaped plastic handle and rubber bit which you put round the sheave and then in a channel in the handle. This gives lots of leverage. You can get them in B&Q.

 

[pmorris]

SUCCESS!
I've found the answer, for anyone with the same problem.

I left them in coca cola for a day. No difference.
I left them in vinegar for a day. No difference.
I gave them to a friend who put them through his sonic cleaner (amazing thing for cleaning carb etc.) three times. NO DIFFERENCE!

I was stumped, didn't know what to do.
So I stuck them in a pot of boiling water on the hob, left them for 15 minutes, took them out and ran them under the cold tap and hey presto they now turn freely.

Water its wonderful stuff.


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