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Masthead Sheave (Read 21 times)
Jonathan
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Bromley
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Masthead Sheave
21.06.2020 at 14:05:02
 
I was so pleased that my club decided it was OK to launch our boats for the season with some easing of the Covid regulations only to find once afloat that there is something wrong at the masthead. Only by maximum effort with longest winch handle can I raise the main. Clearly nothing to do with the luff as it comes down easy enough and pulling on the fall both sides it seems the sheave is rotating but feels more like a flat tyre going bump bump. I am going to get alongside the club jetty where I can dry out for a day and lower the mast not in the heatwave and when wind fairly light.

Hopefully I will be able to remove the sheave without too much trouble. The mast, now 40 years, old is the original I think by Procter and from memory there was a stainless plate held by two self tappers and this carried the spindle. I have not been there for 25 years on the if it ain't broke don't fix it principle so hoping it will come out OK - I see an earlier post of an owner having difficulty with this. It looks to me as though the sources for a new sheave will be Selden who took over Proter I think, Barton who are local at Whitstable or Allen. Between them they seem to have a range of sizes but I have no idea yet what size I need. Width and bore seem to be critical though I guess I could drill out a smaller bore if the width is right.

A lot of the sheaves available are Acetal but I am sure the original is metal. Is it OK to use Acetal for the masthead main halyard? I have replaced most of the deck organiser and mast foot organiser sheaves some with metal and others with Acetal and those seem to be OK but would be easy to replace. This masthead sheave has 4mm wire running over it at all times. Will Acetal put up with that?

I will be grateful for any experiences or possibly suggestions of other sheave makers I have missed.  
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Paul
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Re: Masthead Sheave
Reply #1 - Today at 09:00:48
 
Hi Jonathan,
Your diagnosis of worm out sheave seems logical. I recall my old Proctor mast used a fairly small metal sheave. If you are retaining a wire halliard section I would not use Acetal as its resistance to any fretting movement due to mast moving however slight will be inferior to metal. On Nautibuoy I transferred old Dyneema halliards from original mast into new Z Spars unit.This has a metal sheave I think. The Dyneema is 16 years old and appears good as new. Of course either material for sheave would be fine with Dyneema.

Dell Quay decided on launch early june. With restrictions on who could assist (family members ) and same for sailing about half the boats including

myself decided to sit the season out on the Quay. Might have worked out better early July but fairly short season!

Had thought that earlier prep in March for launch would mean boat all set for 2021 launch but recent visit shows new antifoul is 'washed out ' from vivid to pale blue by rain water.
Does anyone know if this would still be effective ( I suspect not!!!) And whether a pressure wash next March and further coatis the way to go?

Anyhow to those able to sail, enjoy the season, with the hopeful expectation that next year will be much better.

Cheers
Paul
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