Masthead sheave

[alexanick]

Ahoy Mates,
I have a 1970 Cal29. I recently added a Tides bat car system for the mainsail. In doing so, I changed the main halyard from SS wire to rope so that I could extend it to the cockpit. The sheave at the top of the mast was designed for wire or rope but after the changeover, trying to raise the main is very hard. To raise it by hand over hand is next to impossible and that was part of the purpose in making the change. It must be binding in that masthead sheave. How hard is it to install a new one? Suggestions please.

[Jammer]

I had a wire halyard on my 70s era boat.


Many boats from this era have external halyards. If that is the case, you may find that it is a better choice to attach a new block to the masthead fitting somehow (a shackle, wire, rope, maybe a soft shackle) and use the new block. Sheave diameters, widths, and axle sizes weren't standardized and you may trouble finding something that fits the space properly, especially something as low friction as a modern block.


Otherwise if you go to a rigger they can have someone custom-make a sheave, or may offer to replace the entire masthead assembly.

[wholybee]

https://www.zephyrwerks.com/
Will make you a sheave in whatever custom size you need for a reasonable price. Remove your old sheave to take some measurements, and then tell them what size line you want it to work with, and they will cut the sheave to fit that line perfectly.

[Jim Cate]

I've made such a change on my boats in the past and not found any increase in friction. I suspect that your issue is the rope halyard being too large in diameter and dragging on the sides of the sheave box... not the shape of the groove.

The cure is obvious, but pricey!

Jim

[dfelsent]

Originally Posted by Jim Cate

I've made such a change on my boats in the past and not found any increase in friction. I suspect that your issue is the rope halyard being too large in diameter and dragging on the sides of the sheave box... not the shape of the groove.

The cure is obvious, but pricey!

Jim

I think Jim is on a good track. Maybe a dyneema core halyard with a stripped cover to fit in the sheave after the first few feet of hoist. Or just a smaller high tech halyard.

[alexanick]

Thank you for the responses. To Jammer, the halyard is internal so your idea, though a good one, won't work unless I can figure a way to attach it to the mast head or maybe re-rig it so the halyard stays external. In response to Jim, I believe the halyard they gave me with the system is only 3/8 or 7/16. If I remember correctly, which at 75years of age could be a challenge, the sheave was good size and probably could accommodate a larger halyard and it definitely doesn't appear to be rubbing on the sides of the box. If I connect the halyard to a rope and hoist it to the top, it goes up easy-peazy. As soon as I pit some weight on it, it's a struggle. In your respected opinion, do you think having a new combination, wire/rope halyard made, be a better option.

[AKA-None]

Are you certain the trouble isn’t with the sail slides?

[Don C L]

Yeah I bet as Jim says your line is too big. It may be jamming in the groove in the sheave but I doubt that. OR, do you know if those sheaves are the old phenolics? If so you may have done what I did to mine when I switched. The pressure of the halyard in the sheaves popped them apart and they jammed in the box. AND if the box on your old boat is like mine, you may have to order specially sized sheaves to replace the old ones. Contact Ballenger Spars in Watsonville, CA. Great folks and they knew EXACTLY what I was talking about and made me new sheaves. https://ballengerspars.com/contact
I hate to say it, if that is the problem, it is REALLY better to take the mast down to do the work. (YOu may need to do some cleaning inside the box and lining up the bolts and sheaves is more of a hassle when yer 30' up) Not too big a deal for an old boat like ours though

[alexanick]

To AKA,
No, I am not positive the trouble is not with the slides, although I did talk with a rep from Tides Marine and he said that should never be an issue. The slides are made exclusively for their track.
To Don. I do believes the sheave is a metal one. I do intend to repair whatever I have to when the mast is down. Thanks for the contact on Ballenger Spars. I may be needing them

[Dsanduril]

My experience with these are that the sheaves are metal, with something like a 6mm/1/4" groove for the wire at the bottom of a sheave otherwise designed for a 12mm/1/2" rope. Like the "notched" version in the picture below:



We made the exact same conversion at some point in the life of our old boat, from a rope+wire halyard to all rope. If you put any load on it at all the rope can easily get jammed in the groove for the wire. And if the system is old the sheave may not turn easily, causing the rope to jam in there even more.

IIRC when we first swapped over we filled the wire groove with some waxed twine. With the halyard out of the way, just rolled material in there until the groove was full and the sheave presented a reasonable profile for the rope.

The next time the mast was down we changed out the sheave. That shouldn't be a tremendously difficult task, usually complicated by corrosion and finding or making the right size sheave to go back in the masthead. Doing it with the mast up, if you have to drive out an axle pin can be a real challenge.