Can I change the halyard sheaves with the mast in place? I don't need to Unstep the mast for at least 2 yrs. I've never done this before but have no problem with going up the mast. Thx for any info.
Masthead sheaves replacement
- Thread starter FlightRisk1
- Start date
Mast Head Sheaves
Our P42 has a hinged mast head cap that when opened displays two sheaves that slide into a slot. These sheaves, main and topping lift, lift out of their slot and can be replaced. Whether yours is built this way, you will have to climb the stick to find out. Or, contact the mast maker and perhaps they can tell you how they put it together and/or send you replacement sheaves.
What seems to be the problem with the existing sheaves? Why do you think they need to be replaced?
Our P42 has a hinged mast head cap that when opened displays two sheaves that slide into a slot. These sheaves, main and topping lift, lift out of their slot and can be replaced. Whether yours is built this way, you will have to climb the stick to find out. Or, contact the mast maker and perhaps they can tell you how they put it together and/or send you replacement sheaves.
What seems to be the problem with the existing sheaves? Why do you think they need to be replaced?
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Changing sheaves from a bosun's chair does not sound like a fun event. The first thing you will need to do is to rig up a block and line at the masthead that you will be hoisted on the second time you go up. (You're going to have to remove the axle pin that the jib and main halyard probably both use, so you probably can't use the jib or the main halyards.) If you're in luck, the spinnaker halyard might be on its own crane and you can use that one. Once up there, you will have to rig something that will hold the halyards off the old sheaves and keep them out of the way so you can put in the new ones. You will have to free the pin that the sheaves turn on, of course. Often there are small plates on the outside of the mast, screwed over the holes that the pins are inserted through so that the pins don't come out, even if they lose their cotter pins. (Belt and suspenders) The screws are inevitably stainless, and the masts are aluminum. How long did you say they've been electrolysing together up there? The screws are likely quite small - to reduce weight and windage - so removing them without dropping them, or breaking their heads off because their threads are corroded becomes another hurdle. The plates will also fall just as fast as the screws (Gallileo !) If you can get the pins clear, you will probably be able to drive them out with a hammer and a metal punch. Try not to lose the old sheaves down the mast. They might jam an internal halyard somehow, or simply make a racket riccocheting around the inside of the mast in every rough anchorage for the next five years. If the pin is worn, you can now lower yourself down and head to the store for a new one. The third time you go up the mast, you should be able to install the axle pin and the sheaves. Getting them in past the halyards may be tricky, especially if there's any motion in the harbor. It might be a good idea to have some extras in case any go swimming. Then you can reinstall the cotter pins and the covers over the holes. It shouldn't take more than four or five hours.
PaulK,
Thank you that is the best description of what is involved that I've been able to find. Straightforward, clear, no bs. Ok I get it. I'll have to pull the stick to replace them. There are a lot of sources for sheaves and that's helpful.
The main is very difficult to raise. I've lubricated, cleaned, lubed again, inspected everything I can. I'm replacing the main and jib halyards soon with all rope and would like to change the sheaves IF THEY NEED TO BE REPLACED to make the sails slide better. Sheave replacement is not a definate at this point. I'm getting The List together for when the boat gets hauled for bottom job and new thru hulls in Jan. Guess adding Unstep the mast is now on it. Just trying to limit expenses, whatever that is!
Thanks again, I may go up once just to check out how the sheaves are installed, get a loose spin halyard down and change a light bulb or two.
Barbara Hickson
Thank you that is the best description of what is involved that I've been able to find. Straightforward, clear, no bs. Ok I get it. I'll have to pull the stick to replace them. There are a lot of sources for sheaves and that's helpful.
The main is very difficult to raise. I've lubricated, cleaned, lubed again, inspected everything I can. I'm replacing the main and jib halyards soon with all rope and would like to change the sheaves IF THEY NEED TO BE REPLACED to make the sails slide better. Sheave replacement is not a definate at this point. I'm getting The List together for when the boat gets hauled for bottom job and new thru hulls in Jan. Guess adding Unstep the mast is now on it. Just trying to limit expenses, whatever that is!
Thanks again, I may go up once just to check out how the sheaves are installed, get a loose spin halyard down and change a light bulb or two.
Barbara Hickson
A slip mate has one of these. It seems to work better/easier than a bosun chair.
http://www.mastmate.com/
http://www.mastmate.com/
I think it is a very good idea to replace the sheaves, which are probably approaching 30 years old. If I understand, you have wire or wire/rope halyards now. I would expect the sheaves to be worn and even if not, you probably know, the shape and the size of the groove in the sheave is different for wire and rope. There is also the issue of radius. I don't know if the sheaves have anything to do with the difficulty in raising the main 'though. What kind of luff attachment system is there? Slides, T-track, cars, luff wire/groove?
Also it's the worst-case scenario for every step. People do it all the time. I'd just suggest putting string around the old ones so they do not drop down the mast- or overboard.
Shemandr, I believe the main is attached by slides. Definitely not cars or wire. The slides fit into a track in the mast and are stopped by a stopper before they all fall out. Thy are all in good shape and have been lubed well. I plan on replacing said sheaves with u-shaped sheaves as the old ones are for wire to rope halyards.
hello all
I replaced the sheaves in the masthead of my boat.... there was one large sheave and it went through the entire mast at the top... I replaced it with 2 smaller sheaves.... I then ran the halyards down the inside of the mast... I then cut openings and attached guides for the halyards to exit the mast about 2 ft from the base.... it works great... the old single big sheave was for rope and wire.... the new sheaves are for rope only... now I have 3 halyards and 1 topping lift attached to the top of my mast... before, the mast only held 2 halyards....
this arrangement gives me a much batter configuration for sailing, with more options....
sincerely
Jess
I replaced the sheaves in the masthead of my boat.... there was one large sheave and it went through the entire mast at the top... I replaced it with 2 smaller sheaves.... I then ran the halyards down the inside of the mast... I then cut openings and attached guides for the halyards to exit the mast about 2 ft from the base.... it works great... the old single big sheave was for rope and wire.... the new sheaves are for rope only... now I have 3 halyards and 1 topping lift attached to the top of my mast... before, the mast only held 2 halyards....
this arrangement gives me a much batter configuration for sailing, with more options....
sincerely
Jess