Sheave at Masthead?

[Calypso52]

The sticks are out this year, getting a thorough going over. One project is to replace the running rigging, especially the indeterminate age wire to rope halyards. They are probably fine but I just don't trust them.

The masthead sheave has a smaller groove for the wire and a larger one for the rope. My rigger suggests that the sheave should be removed and machined to remove the groove for the wire. Otherwise the new 1/2" halyard will be trying to lay in that wire groove when tensioned, potentially causing premature failure of the halyard.

So of course, that sheave has not been out of the masthead since 1977. The end that had a little cover plate riveted over it is ground flat to the mast. No sign of the other end on the opposite side. Anyone know how the masthead was constructed back then? Some kind of blind socket on the other end? I suspect I am just going to have to use the sheave as is. The only alternative I can envision is to have a welder put a stud on the end I can see, but that sounds like way too much cost and work and no guarantee of getting it out. Thoughts? Thanks!

[capt-couillon]

A rigger (like any good mechanic) operates on the premise of "If in doubt, throw it out". Prevents customers coming back next year saying "You said it was OK" when a part fails. Not criticizing your rigger, just sayin...

Halyard loads are really not that high... Most halyards are larger diameter than strength requires due to the fact an average human hand has a hard time hauling a line under 3/8". As long as the "rope groove" is of adequate depth and radius for the proposed line size, the narrower slot below will not cause additional wear under normal loads. If one wanted to get real anal, I suppose a piece of line of the appropriate diameter could be glued in the slot for additional support, but in my opinion, unnecessary.

Of course, it is always good practice for any line used with a fixed stress point to be installed with some extra length available. This allows the line to be shortened occasionally, moving the stress point to a new location on the line.

For a 27 Catalina, I would not bother with the cost of a sexy ultra low stretch line. I have been using NovaBraid XLS (Comparable with Samson XLS or Sta-Set) for all my halyards and sheets on a similar class vessel with no real problems from stretch or creep in the halyards.

Hope this helps

[toddedger]

I would drill a hole in the other side just big enough for and punch, and drive it out. It's not going to get any easier as time goes on. The two thick plates hold the pin load, and the pin usually just buts up against the inner wall of the mast. Sometimes the cover plate is welded to the end of the pin so you have something to pry at to get in out. My mast has a hole in both sides with washers and cotter pins holding it in. 1977 would be a long time for not inspecting the bearing surfaces. I just purchased some sheaves from Garhauer for the same reason. They were $53 each.

[Fiveslide]

I would start by spraying with a penatrating oil and lightly tapping the pin to help the oil penetrate, every time I walked by the mast. Did this for a weekend and my pins popped right out with a punch.

Like toddedger, I made the switch to pins with cotter pins, I check the cotter pins and sheaves more often but it will now be a job of just a few minutes to install new sheaves when it is needed.

Considering the age of the sheaves, that they were meant for wire-to-rope and are currently so wonderfully close to the ground, I would try to swap them for new ones before stepping the mast again.

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[Fiveslide]

After some thought, I don't think welding a stud on it is the solution. A few dollars spent on materials and a puller can be made.

If the pin is large enough, and you're carefull, you could drill and tap some threads into it. Screw in about a half a foot of the appropriate size all-thread. Slide a socket or something with a hole large enough for the pin over the all-thread. Then a washer and nut on the all thread. Tighten the nut down against the socket or whatever you used and the force should pull the pin straight out.

Then you could either re-use the old pressed in pin or drill through all the holes for a new pin all the way through the mast with cotter pins.

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[osprey877]

re your original question about what does the sheave/pin arrangement look like: Have you checked out the rigrite website? they have a lot of info, including part numbers and diagrams, for most production masts. if not, google "rigrite".

[Stumble]

You are getting way to complicated with this. Just drive or drill out the sheave and put in a stainless pin with cotter pins.

As for milling out the sheave... That is truly a bizarre and expensive idea. Either buy a new one of the appropriate size, or you can get custom new ones made for about $30 from Zephyrwerks - The Sheave Factory .

For your halyard... Do yourself a favor and switch to a tapered endurabraid halyard. The smaller size will run easier, you will save money, and on a 50' boat the stretch mitigation will be substantial. I appreciate wanting a large enough line for a good hand, but there is no reason to go all the way to 1/2".

[bornyesterday]

A cover plate over only one end of the pin strongly suggests that the other end sits in a blind hole.

If you can borrow or buy a slide hammer (auto body shop tool) you can just drill the exposed pin end for a self-tapping screw which you then pull with the slide hammer.

If it's corroded in place (stainless in alloy) then drill the mast opposite the exposed pin and use a hammer and drift to tap out the pin.

I'd avoid using a hydraulic/screw press or puller on an alloy mast - much rather have to drill the whole pin out than risk squashing the mast.

Wouldn't use heat either...

[Terra Nova]

The sheave and pin must be removed. Cleanup the area around the pin cap to see what is holding it in place and why someone Bubba'd it with a grinder. Soak it with AeroKroil. If possible, remove the pin without drilling the other side.

[Jim Cate]

Here's another vote for replacing the sheave. Not just because of the wire groove, for we have often put rope halyards on such sheaves with no problems, but really because at that age the bushing (almost certainly a bronze bushing for a bearing in that sheave) will be worn and corroded. You will be amazed at how much easier the sail will be to hoist, especially if you spring for a ball or roller bearing sheave as a replacement.

Now is the time... think of trying to do this job hanging up at the masthead in a bosun's chair!

Cheers,

Jim

[roverhi]

Have done more than 10,000 miles sailing with composite rope/wire sheaves with rope halyards. They work just fine.

Looks like the pin does indeed fit into a blind socket on one side as you surmised. Probably is a lot more trouble to remove it than to leave it in place as long as the sheave rotates freely on the axle/pin. If it doesn't, removing it and freeing it up is definitely in order. If you decide to replace the sheave, Garhauer is probably the most reasonable sourc in the US.