Topic: new masthead halyard sheaves

Hello Everyone,

I just read in Toss's Rigger's Apprentice book that my sheaves at the masthead need to be replaced because I changed the halyards from the steel cable/rope kind to the all rope kind.  The book says that the halyards will experience excessive chafe as they are pulled into the little groove that was meant for the steel cable.  Seems to make sense.  So I'm shopping for new sheaves and having difficulty finding some that are the right size.  The old ones are 2 5/8" outside diameter and 5/8" wide with a 3/8" diameter shaft but all I'm finding for sale at places like Defender are 2" outside diameter sheaves made of delrin, etc.  And when I made a little 2" cardboard sheave to see if I could just go ahead and use a somewhat smaller sheave, it doesn't look like it will work because the rope will chafe on the track on the mast. 

Has anyone faced this issue when they replaced their old halyards with all rope halyards?  And if so, where did you buy 2 5/8" sheaves like the ones that you are replacing (except no groove for steel cable)?

thanks much,

Brian

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Re: new masthead halyard sheaves

Brian

A wild stab in the dark as I have no experience with the first link and have limited experience with the second;
You could try inquiring at;
http://www.riggingonly.com/
and
http://www.hollandmarine.com/

Holland Marine has a reputation for have one off pieces for sale that are hard to find elsewhere.

John

Re: new masthead halyard sheaves

John,

Thanks for the tips.........I'll give 'em a try.

B

Re: new masthead halyard sheaves

Does anyone know what material these original sheaves are made out of?
As you can see from the photo, they are brown in color and look like they are reinforced with a cross pattern of fibers and the edges seem course.  I'm wondering if they are fiberglass?

B

5 (edited by bertinol 2014-02-22 09:09:27)

Re: new masthead halyard sheaves

The brown sheaves are Tufnol, a very good British product made of linen soaked in resin with a brass bushing in the middle. That may sound bizarre but they were - and are-- very good, and they do last forever, far longer than Harken and Ronstan. I've bought a couple of sheaves and blocks at garage sales because they work well and they make the boat look period, but you can also get them new from Gordon Laco  at mainstay@csolve.net.  He's the Canadian importer for a wide range of olde worlde Tufnol, bronze and brass cleats, fairleads, oarlocks and other nifty bits.

You can get aluminum sheaves from any good chandler. Several people still make them. Or just find a friend with a lathe and make your own in five minutes.

If you like industrial history, check out http://ahistoryoftufnol.org/index.html or the company website.

6 (edited by Ian Malcolm 2014-02-22 13:27:51)

Re: new masthead halyard sheaves

Got an edge on view of the sheave?  It *may* just be possible to clean out the wire groove then build it up with epoxy and Kevlar roving to an acceptable profile.   

Otherwise any competent machine shop could duplicate the sheave in Tufnol with a press-fit Oilite bronze bushing.   Unless the pin is in excellent condition, it needs replacing at the same time as if it is worn the new bushing will rapidly degrade due to uneven loading.

Be aware the pin may not be true in the sheave box and this can result in a new or rebushed sheave jamming under load or even the need to increase clearances excessively to get the sheave to turn freely. You may need thin washers cut from UHMWPE sheet (preferably molybdenum disulphide impregnated UHMWPE) to take the side loading and prevent jamming.

Re: new masthead halyard sheaves

Here's a edge view photo of the sheave

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Re: new masthead halyard sheaves

I finally decided to just go for it and see if I could reshape the old sheaves (especially after the $80 a piece quote from Rigrite.com).  I found a small grinding wheel in the bottom of one of my toolboxes that was made to chuck up in a rotozip type rotory tool.  I used a small cardboard cutout with the negative profile of a 1/2" semicircle to shape the grinding wheel carefully until I had it just right.  Then, I chucked the grinding wheel up in my router and laid it on its side and just held the sheave up against the wheel by hand, letting the pull of the wheel spin the sheave slowly as it ground away.  As you can see from the photo, the new sheaves have a rope groove.  One sheave is somewhat smaller than the others because the wire had dug deeper into the Tufnol.  Since the sheaves on the front of the mast don't need as much clearance as the ones on the back, this is where I will install the smaller sheave.  I check and discovered that the clearance is fine.  The only cost to this project are some small cuts on the ends of three of my fingers from edge of the spinning bronze bushing as I held it to the grinding wheel. 

Thanks everyone for all the excellent comments on this thread!

B

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Re: new masthead halyard sheaves

I forgot to mention that I used a small diamond dresser to shape the grinding wheel.

Cheers

B

Re: new masthead halyard sheaves

Hooray!

It's much more rewarding to make your parts than to buy new ones.  Cheaper too!

Re: new masthead halyard sheaves

Bravo!  Nice work!

Re: new masthead halyard sheaves

Has anyone considered making narrower sheaves? 

I was looking into replacing the halyards on my Contessa with high tech ropes and realized that I could come down several sizes and retain both the strength and durability of the ropes.  I think I could squeeze a third set of sheaves at the top of my mast using this approach which would give me a spare halyard or sturdier topping lift.

13 (edited by Ian Malcolm 2014-02-27 07:38:07)

Re: new masthead halyard sheaves

It very much depends on the sheaveboxes.   Mine are welded into the masthead and are constructed of aluminium plate with a divider between the main and genoa halyard sheaves so there is no way of adding a third sheave unless I was to go down to under half width sheaves.   Also you are vastly increasing the risk of a halyard jumping its sheave and jamming not only itself but the adjacent sheave as well.

Your topping lift and spinny halyard ropes blocks and fittings should all be strong enough to go up the mast on if you have to, and if you ever need to be towed off a shoal by a small workboat or a RIB, you will worry a lot less if your spinny halyard and block have the same breaking load as your cap shroud.