Need help on masthead sheave replacement information - SailNet Community
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post #1 of 14 Old 11-13-2015 Thread Starter
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Need help on masthead sheave replacement information

The main halyard sheave in my masthead assembly needs replacement and I'd like to find out information on its size and best sources of such sheaves. My boat is a 1984 Pacific Seacraft Orion. Can anybody help? I've got a question in on the Orion Users group website but would like to reach out to a broader audience and experience set. I welcome suggestions on best sheave materials or any other advice - before I head up the mast. Thanks in advance!
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post #2 of 14 Old 11-13-2015
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Re: Need help on masthead sheave replacement information

You can remove the faulty sheave from the masthead and have a new one custom made to size. In this article I provide the details on how I did this on my boat, Oystercatcher.

Ericson 25, Oystercatcher: Rigging, Running, Wire-Rope Halyard to All-Rope Halyard Conversion

Roscoe

Roscoe
Ericson 25, #226
Oystercatcher

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post #3 of 14 Old 11-13-2015
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Re: Need help on masthead sheave replacement information

The procedure and the ease of which this can be done depends greatly on the design of the masthead fittings and the pin holding the sheaves.

Having a new sheave machined should not be complicated, esp if you have an old one out for comparison. However changing it aloft will be a challenge, and obviously you can't do it hanging on that particular halyard.

I'd imagine that PSC used a standard mast supplier - if you're luck they are still in business and might advise/even have parts.

Some pictures of your setup would be very helpful.

Ron

1984 Fast/Nicholson 345 "FastForward"

".. there is much you could do at sea with common sense.. and very little you could do without it.."
Capt G E Ericson (from "The Cruel Sea" by Nicholas Monsarrat)
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post #4 of 14 Old 11-15-2015
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Re: Need help on masthead sheave replacement information

Sorry, can't lead you to the correct parts, but will mention that when I replaced the sheaves on my Catalina 28 I used plain bearings for the halyards that don't get used often, and used a ball bearing sheave for the main, which gets used a lot. Very smooth.

Good luck.
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Re: Need help on masthead sheave replacement information

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Re: Need help on masthead sheave replacement information

Thanks everybody for the information so far. I'm attaching some pictures of the masthead assembly when the mast was down a year ago. A ball bearing sheave would certainly be nice.
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P1030979.jpg   P1030980.jpg   P1030977.jpg  
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post #7 of 14 Old 11-15-2015
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Re: Need help on masthead sheave replacement information

The photos look quite similar to my masthead sheaves. Mine is a LeFiell mast, and they're still in business. The sheaves look like aluminum, as are mine. Yours, too, are cut for wire-and-rope halyards (ditto).
My sheaves are aluminum with bronze bushings. They're bullet-proof. If still in good shape, they're better than new plastic ones. New aluminum sheaves are very costly. The bushings are really the only parts that are likely to wear much, and they can be replaced easily by a machine shop if necessary. Mine, in use since '79, didn't require that.
I'd prefer bushings to bearings. Simpler, more robust, fewer parts to wear, corrode or stick. Remember that most of the time they're stationary, and under stress.
I suggest you do as I did and pull them before you decide whether to replace them. May just look a little ugly on the surface.
Your larger problem may be the secondary groove, if you use all-rope halyards. The small inner groove will damage your rope halyards in time. I found my sheave diameters to be large enough that I could have the grooves re-cut to round profiles at a local machine shop for all-rope use for about $10 each. They had to shave about 1/4 inch from the original diameters. They were like new when I re-mounted them with a little silicone grease.
You may find, as I did, that you're actually lucky to have the ones that are there now.
If your mast is still up, be very careful not to lose the sheaves or the aluminum plates between them when you pull the pins out.
JV

Last edited by VallelyJ; 11-15-2015 at 02:56 PM.
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Re: Need help on masthead sheave replacement information

I replaced my sheaves last summer. On my 1980 Hunter it required dropping the mast, so I took the opportunity to replace all 4 sheaves, standing rigging, and in mast wiring (including switching to LED lighting). A small marine machine shop made the sheaves for me for a very reasonable price. A local rigger made the shrouds using the old shrouds as a template, and I did all of the assembly and adjustment. All told, total costs including yard charges for crane and yard time, and miscellaneous supplies, were less than $2,000.
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Re: Need help on masthead sheave replacement information

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Originally Posted by rhs View Post
Thanks everybody for the information so far. I'm attaching some pictures of the masthead assembly when the mast was down a year ago. A ball bearing sheave would certainly be nice.
Looks like your sheave shafts are easily accessible and removeable, that helps. However it looks tricky to do aloft, if that's your intention, and also looks like some pins need to come out besides to actually pull the sheaves out.

This would be a lot easier to do with the mast down.. esp if you tend to drop things like I do....

Ron

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Re: Need help on masthead sheave replacement information

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and also looks like some pins need to come out besides to actually pull the sheaves out.
This would be a lot easier to do with the mast down.. esp if you tend to drop things like I do....
Ditto that.
The pins are a tight fit and I had to drive them out. Put a long screwdriver through them before you push them out. That will keep the sheaves and dividers from falling into the mast. Tie a string or wire around each sheave before you pull the pins so you don't need a 3rd hand to grip them. It was a bigger PIA than it looks.
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