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Old 05-13-2013
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Masthead Sheaves

Hello all -

We have a Columbia Challenger, built in 1964, hull #248 that we acquired last year and we are finding lots of small projects.

The current project:

We had some difficulty with the halyards when we first got her, and first I tried a new main halyard. That worked well, but there started to be problems with the jib halyard (now it's "Done"), which was working at first Now the main halyard is also showing signs of "Binding."

I finally got up to the top of the mast and had a good look at the sheaves in the masthead box, and they were all frozen. I took the whole box apart Saturday, and what I found was that there is one bolt that I would call a "Tensioner" bolt, that someone overtightened and that's what caused all the sheaves to be frozen. And, taking it apart ruined all the sheaves that were there, since I pried the two forward ones out before realizing I could release the tension on that through bolt and get them out more easily.

Anyhow, The original rig had wire, but the halyards were converted to rope at some point, though it doesn't appear to me that anybody changed the sheaves. They are plastic, brown in color, like they're made of some fibrous material. We have other blocks on the boat that are made of the same material, though I'd rather go with something stronger - if it will fit. They have a V-shaped groove, that can accommodate at most 1/4" line it looks like to me.

The halyards are both 3/8" line (my newer main is a pretty ordinary Polyester Double Braid Pre-Spliced pre-made Halyard from Jamestown), but the wire that was original was 3/16" (I have a snap shackle from the original jib halyard with a piece of wire still attached). So, I'm wondering if I can find sheaves, like a Harken or Schaefer style, made of stronger plastic, probably without a bushing or bearings though to fit this application?

The dimensions I've measured are:

Diameter of sheaves: 2" (most often referred to as "A")
Width of sheaves: 7/16" (often referred to as "B")
Width of supporting plate in center of masthead box: 3/16"
Diameter of sheave pins: 3/8" (usually referred to as "C")

There are problems. Whoever it was that overtightened the tensioner bolt on the masthead box, cracked the box on one side. The crack runs from the bolt directly upwards, so there is no load bearing on any cracked surfaces, but it's not good, likely the entire box needs replacing at some point. I cannot tell if the box is welded on, but it's corroded on at the very least and will require dropping the mast to replace. Not a big task, but I've not had the opportunity to get the mast down yet.

The total inner width of the masthead sheave box is 17/16" from inside to inside which is adequate to have 3/8" line running through - even with the 3/16" supporting plate in the center. But I don't see any sheaves at all that will fit the 7/16" requirement for width that will run 3/8" line (off-the-shelf) on any of the popular sailing hardware online sites. I may need to get a sheave that actually is more like 1 7/8" diameter to properly support that diameter line for the halyards. I'm not an expert in sailing really, but I understand engineering pretty well (I'm a software engineer by trade, I can read mechanical diagrams and specs).

I think what I need is a sheave that is more flattened on the running surface, rather than V-grooved? I see there are many like that available, but not in smaller sizes, and nothing that will fit that 7/16" width requirement. I'd love to have custom aluminum or steel sheaves in there, but that would be expensive. The other option is to get higher quality line and go with a lesser diameter line, such as dyneema or one of the other more modern and exotic types but those are all so expensive as well. If I don't get some kind of solution, I will keep ruining halyards rather quickly and that's no good either.

If I took the mast down, I could put on a new sheave box and even go so far as to run halyards internally, but that's a ton of work, none of which I am qualified to do, so that looks to be even MORE expensive.

I understand the options, I need something reasonable, and am willing to keep the external halyards for now, and try to keep the existing box functional until I can replace it with an upgrade or a like replacement.

Does anyone know of a place on the Internet that can fit me out with some relatively inexpensive custom sheaves to fit this application?

The problem for us amateur sailors is finding the right resources for the problem at hand. We have a local boat yard of course, but that would be considered likely my most expensive resource at this point. We will be hauling out in the next year or so, and that is likely when the mast will come down as well.

Thanks so much in advance.
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Old 05-13-2013
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Re: Masthead Sheaves

Have you checked at McMaster-Carr?
McMaster-Carr
Hint: if you find a stock sheave that is close to the dimensions you need you can mill most synthetic sheaves (delrin, nylon etc.) to fit your application.
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Old 05-13-2013
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Re: Masthead Sheaves

Zephyrwerks - The Sheave Factory
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Re: Masthead Sheaves

Quote:
Originally Posted by sdebeaubien View Post
Hello all -

We have a Columbia Challenger, built in 1964, hull #248 that we acquired last year and we are finding lots of small projects.

The current project:

We had some difficulty with the halyards when we first got her, and first I tried a new main halyard. That worked well, but there started to be problems with the jib halyard (now it's "Done"), which was working at first Now the main halyard is also showing signs of "Binding."

I finally got up to the top of the mast and had a good look at the sheaves in the masthead box, and they were all frozen. I took the whole box apart Saturday, and what I found was that there is one bolt that I would call a "Tensioner" bolt, that someone overtightened and that's what caused all the sheaves to be frozen. And, taking it apart ruined all the sheaves that were there, since I pried the two forward ones out before realizing I could release the tension on that through bolt and get them out more easily.

Anyhow, The original rig had wire, but the halyards were converted to rope at some point, though it doesn't appear to me that anybody changed the sheaves. They are plastic, brown in color, like they're made of some fibrous material. We have other blocks on the boat that are made of the same material, though I'd rather go with something stronger - if it will fit. They have a V-shaped groove, that can accommodate at most 1/4" line it looks like to me.

The halyards are both 3/8" line (my newer main is a pretty ordinary Polyester Double Braid Pre-Spliced pre-made Halyard from Jamestown), but the wire that was original was 3/16" (I have a snap shackle from the original jib halyard with a piece of wire still attached). So, I'm wondering if I can find sheaves, like a Harken or Schaefer style, made of stronger plastic, probably without a bushing or bearings though to fit this application?

The dimensions I've measured are:

Diameter of sheaves: 2" (most often referred to as "A")
Width of sheaves: 7/16" (often referred to as "B")
Width of supporting plate in center of masthead box: 3/16"
Diameter of sheave pins: 3/8" (usually referred to as "C")

There are problems. Whoever it was that overtightened the tensioner bolt on the masthead box, cracked the box on one side. The crack runs from the bolt directly upwards, so there is no load bearing on any cracked surfaces, but it's not good, likely the entire box needs replacing at some point. I cannot tell if the box is welded on, but it's corroded on at the very least and will require dropping the mast to replace. Not a big task, but I've not had the opportunity to get the mast down yet.

The total inner width of the masthead sheave box is 17/16" from inside to inside which is adequate to have 3/8" line running through - even with the 3/16" supporting plate in the center. But I don't see any sheaves at all that will fit the 7/16" requirement for width that will run 3/8" line (off-the-shelf) on any of the popular sailing hardware online sites. I may need to get a sheave that actually is more like 1 7/8" diameter to properly support that diameter line for the halyards. I'm not an expert in sailing really, but I understand engineering pretty well (I'm a software engineer by trade, I can read mechanical diagrams and specs).

I think what I need is a sheave that is more flattened on the running surface, rather than V-grooved? I see there are many like that available, but not in smaller sizes, and nothing that will fit that 7/16" width requirement. I'd love to have custom aluminum or steel sheaves in there, but that would be expensive. The other option is to get higher quality line and go with a lesser diameter line, such as dyneema or one of the other more modern and exotic types but those are all so expensive as well. If I don't get some kind of solution, I will keep ruining halyards rather quickly and that's no good either.

If I took the mast down, I could put on a new sheave box and even go so far as to run halyards internally, but that's a ton of work, none of which I am qualified to do, so that looks to be even MORE expensive.

I understand the options, I need something reasonable, and am willing to keep the external halyards for now, and try to keep the existing box functional until I can replace it with an upgrade or a like replacement.

Does anyone know of a place on the Internet that can fit me out with some relatively inexpensive custom sheaves to fit this application?

The problem for us amateur sailors is finding the right resources for the problem at hand. We have a local boat yard of course, but that would be considered likely my most expensive resource at this point. We will be hauling out in the next year or so, and that is likely when the mast will come down as well.

Thanks so much in advance.
Zephyrwerks - The Sheave Factory is good but not inexpensive. If you are running 3/8" line, you want sheaves that are U-shaped. The most inexpensive way is to get some plate aluminum and make them yourself. Failing that, a local machine shop could make them up for you. They could also be made from a hard plastic like Delrin or Nylon.

Great first post by the way.
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Old 05-13-2013
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Re: Masthead Sheaves

I have no connection to Zephyrwerks. but it is the way to go you call him and you get the correct sheave made for marine use in less then a week. 2" sheaves are about $ 40. a machine shop is going to charge at least that and you have to do the designing. for most it will cost more for the gas to drive around looking for materials then the sheave cost.
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Re: Masthead Sheaves

Sending an email to Zephyrworks with the dimensions, we will see if they think they can build it to work with 3/8" line inside that box.

I'll post their reply.
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Old 05-13-2013
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Re: Masthead Sheaves

Columbia, '64 vintage, probably machined phenolic. Your new Zephyrworks will be light years ahead. Sail on
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Old 05-14-2013
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Re: Masthead Sheaves

The URL is spelled a little differently Zephyrwerks - The Sheave Factory
Used them 2 years ago to replace all my masthead sheaves for the same reason as sdebeaubien. They could not have given better service, and with a cost of less than half of what stock (almost the right size) sheaves would have cost me.
YES, a big endorsement for them...and NO I am not related to anyone there.
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Old 05-14-2013
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Re: Masthead Sheaves

Thanks all.

Yes indeed, Zephyrwerks got back to me right away, with a very respectable quote, all new sheaves, pins and center supporting plate. They'll build the new plate thin enough to fit sheaves in there for the 3/8" line - which in the long run saves me the most because that halyard line can be had cheaply and is common and completely adequate for the age and type of vessel we're talking about here.

I'm shipping them off the box of old parts today so they have the exact dimensions for the plate and the pins, etc...

Machined phenolic, eh? That's what those old sheaves are. Still have a few blocks on the boat made of that material, I don't see it sold anywhere anymore, must have gone the way of dinosaurs. Many materials out there stronger, lighter, more durable and longer lasting these days.

My one issue remaining is the crack on top of the tensioner bolt in the masthead box which I think for now, I will install a strap across it in case it happens to give out anytime soon... I will get a better look at it when the mast is down when we haul out maybe in the Fall.
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Old 05-19-2013
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Re: Masthead Sheaves

I hope I DON'T need all this info, but I'm glad it's here. My jib halyard has a lot of friction to it right now... thanks.

Barry
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