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Author Topic: Mast Head Sheave Plate - necessary?  (Read 1994 times)

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C Martinson

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Mast Head Sheave Plate - necessary?
« on: April 27, 2009, 04:11:21 PM »

Before I start....I took the mast head off my mast to clean it and try to get the sheaves to work better.  My masthead has a sheave, plate that separates the sheaves and then the other sheave.

Has anyone had an issue with the sheaves in the mast head binding against the plate?  I took the sheaves and plates out and cleaned them and without the plate in the sheaves move easily.  However - once I put the plate in they seem to bind.  I found a shop to plane these plates down - he didn't have the thinner material in stock and I go in May 4th....hopefully the thinning of the plates will fix the problem.  I briefly thought of leaving the plate out but am concerned about the halyards jumping the sheave or getting jambed in between the sheaves.....any thoughts on this?

Thanks

Chris Martinson
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1989 Hull 945
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waterdog

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Re: Mast Head Sheave Plate - necessary?
« Reply #1 on: April 27, 2009, 05:15:36 PM »

You need the plate or halyards will jump and bind - and at that point it will be hard to get up the mast to fix it. 

Did you put the same sheaves back in the same spots?   I ran into exactly the problem you are having.   It turned out that they weren't all the same thickness.   Try swapping them around until you get a non binding combination front and back and left and right.   Make sure you have no wobble on the pins.   They should turn freely without any wobble.   If they wobble, you need new bushings.   

It's almost as though they built the box too tight and machined down sheaves on one side to make it work.   Put a caliper on them if you want to be sure...




« Last Edit: April 27, 2009, 10:36:08 PM by waterdog »
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Steve Dolling
Former 1988 #804, BlackDragon - Vancouver BC
Now 1999 Manta 40 cat

Ron Hill

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Re: Mast Head Sheave Plate - necessary?
« Reply #2 on: April 27, 2009, 05:38:42 PM »

Chris : Hope that you contacted Gaurhauer Marine and got ball bearing sheaves to replace your old ones. That would take care of any bushing wear that has been mentioned.   A thought.
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Mike and Joanne Stimmler

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Re: Mast Head Sheave Plate - necessary?
« Reply #3 on: April 27, 2009, 08:38:08 PM »


       I think we should all sing:

                              "Bringing in the Sheaves"       :party

                     
                                 Sorry, I just couldn't help myself
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Mike and Joanne Stimmler
Former owner of Calerpitter
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waterdog

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Re: Mast Head Sheave Plate - necessary?
« Reply #4 on: April 27, 2009, 10:33:30 PM »

Chris : Hope that you contacted Gaurhauer Marine and got ball bearing sheaves to replace your old ones. That would take care of any bushing wear that has been mentioned.   A thought.

Bushings can be good for a long time.   They can get wobbly over 20 years causing some friction between the sheaves and the walls of the mast box.   Easily maintained (with the mast out).   Graceful, long term failure.  Exactly what you want at the top of your mast.

 What is the failure mode on the bearings and how long do they last?   
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Steve Dolling
Former 1988 #804, BlackDragon - Vancouver BC
Now 1999 Manta 40 cat
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