Refurbishing a mast box

[Sea Change]

I've been having problems with halyards not running smoothly so with the mast down for winter, I've removed the fabricated box at the top which holds the four sheaves.
The boat is a 1980s Jeanneau and I believe the spars are from Francespar.

The problem was pretty obvious- there's a thin (c.1.5mm) aluminium plate running fore/aft inside the box, and this serves as the divider between the sheaves. Over the years it's been worn away to the point where it was breaking up, and bits of it were bent out of shape and interfering with the halyards.

Obviously I could just replace it with another sheet of thin aluminium, and it would presumably last another 40yrs. But I'm wondering if it would be a better idea to use some sort of hard plastic? It would have less friction for the sheaves, although it might not last as long.

I can't be the only person who has had to do this?

 

[geem]

I've been having problems with halyards not running smoothly so with the mast down for winter, I've removed the fabricated box at the top which holds the four sheaves.
The boat is a 1980s Jeanneau and I believe the spars are from Francespar.

The problem was pretty obvious- there's a thin (c.1.5mm) aluminium plate running fore/aft inside the box, and this serves as the divider between the sheaves. Over the years it's been worn away to the point where it was breaking up, and bits of it were bent out of shape and interfering with the halyards.

Obviously I could just replace it with another sheet of thin aluminium, and it would presumably last another 40yrs. But I'm wondering if it would be a better idea to use some sort of hard plastic? It would have less friction for the sheaves, although it might not last as long.

I can't be the only person who has had to do this?

You would need some plastic that was very UV resistant. I would stick to aluminium

 

[BabaYaga]

But I'm wondering if it would be a better idea to use some sort of hard plastic? It would have less friction for the sheaves, although it might not last as long.

In the box of my Selden mast of similar age the divider is made from what looks like tufnol sheet, maybe 2mm thick. This looked fine when I had the box off to replace the sheaves a couple of years ago.

 

[Sea Change]

You would need some plastic that was very UV resistant. I would stick to aluminium

I mustn't have explained it properly, there is almost no UV exposure. The divider is entirely inside the mast box.

 

[BabaYaga]

I mustn't have explained it properly, there is almost no UV exposure. The divider is entirely inside the mast box.

I should clarify that on my Selden mast box, the divider is indeed exposed to UV, at least the upper part. Also, tufnol is my best guess, the divider is brownish and definitely not metal.

 

[Sea Change]

I should clarify that on my Selden mast box, the divider is indeed exposed to UV, at least the upper part. Also, tufnol is my best guess, the divider is brownish and definitely not metal.

I can't see much if any UV getting inside the mast box on the design I have. Or maybe the plate was originally much bigger and some of it was visible? But what's left of it is sandwiched between the sheaves.

 

[geem]

I can't see much if any UV getting inside the mast box on the design I have. Or maybe the plate was originally much bigger and some of it was visible? But what's left of it is sandwiched between the sheaves.

The dividers on my mast box is 6mm thick and a structural part of the mast. It is exposed where the halyards exit. Front and back.

 

[Sea Change]

This one is only 1.5mm thick. I presume it's only there to stop the halyards from being able to jump on to the wrong sheave if a lateral load is placed on them.