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Old 17-03-2016, 15:49   #1
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Removing Masthead Sheaves

I am trying to replace my tired wire to rope halyards and sheaves, but so far have not been able to get them out. there are covers secured by 2 self tapping screws that are over the pin, one cover on each side of the mast, but I cant get them to budge. I was able to get a chisel under one side of the cover, but when I started to pry, the metal started to bend. any ideas of how to proceed would be greatly appreciated.
Thanks in advance.

Tom
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Old 17-03-2016, 17:09   #2
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Re: Removing Masthead Sheaves

I guess you meant that the mast section was bending, not the cap. From now on, i'd consider the cap replaceable, since you have to get it off to continue the job. You're going to have to wedge it off, once you get a corner loose, you'll have a better chance. It doesn't look like you have a lot of dissimilar metal corrosion under it, which is good. Maybe if you start with small screwdrivers, their leading edge narrower than the chisel, and shift to the chisel after you've started it up? Fwiw, my sense of it is that you're gonna have to use fair means or foul to pry it off.

Since we don't know what's holding it on (was it put on with sealant for the galvanic corrosion barrier?, it is hard to recommend a product that might help.

Hope it turns loose fast.

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Old 17-03-2016, 17:41   #3
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Re: Removing Masthead Sheaves

Tom, do you mean that there is a plate on each end of a single pin, or that there are two pins, each with a cover plate?

If the latter, I seem to recall that on a mast owned long-ago, the cover plate was welded to the pin, and was used to both locate it and to withdraw it from the mast. If yours is that sort, it would indicate that the pin is seized internally, possibly where it passes through the central web. And if that is the case, it may be a bitch to get out! Heat and force are required and heating such a big chunk of aluminium will be hard.

Another approach might be to try and use an adjustable wrench on the sides of the plate and rotate it around the pin. Or sometimes there will be an access hole on the opposite side of the masthead, and you can use a drift and a hammer to drive the pin out.

At any rate, I wish you luck in getting it apart. Aluminium can be treacherous!

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Old 17-03-2016, 17:41   #4
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Re: Removing Masthead Sheaves

On mine that is the Head for the axel pin...not just a cover...try rotation...spray pb blaster, wd-40 repeat


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Old 17-03-2016, 18:04   #5
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Re: Removing Masthead Sheaves

Kroil penetrant, spray the sheaves through the line slot and behind the plates, which are welded to pins inserted through the mast head into the inner body of the masthead.
Yes they should turn, they are stuck.


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Old 17-03-2016, 18:49   #6
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Re: Removing Masthead Sheaves

Thanks everyone. I thought they may be part of the pin, and since they are on both sides of the mast, they are probably 2 pins, one for each sheave. I did manage to get under one of the covers, and as I worked the chisel around under it it just bent. Since the halyards are still in place I don't want to try heat, but I will try Kroll or PB blaster. using an adjustable wrench to twist them may help.
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Old 19-03-2016, 17:05   #7
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Re: Removing Masthead Sheaves

Quote:
Originally Posted by tsell View Post
Thanks everyone. I thought they may be part of the pin, and since they are on both sides of the mast, they are probably 2 pins, one for each sheave. I did manage to get under one of the covers, and as I worked the chisel around under it it just bent. Since the halyards are still in place I don't want to try heat, but I will try Kroll or PB blaster. using an adjustable wrench to twist them may help.

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Old 19-03-2016, 18:27   #8
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Re: Removing Masthead Sheaves

Post more photos around and on top. Thanks
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Old 19-03-2016, 20:52   #9
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Re: Removing Masthead Sheaves

Since you're tossing the sheaves anyway, my vote is to:
- Yank out the halyards. And perhaps replace them with some wire for the moment (to use later as leaders). So that you have more room to...
- Ginsu (cut) the sheaves in half, in place. Followed by yanking out, & tossing said scrap metal.

Then you'll have more room to work, & a much clearer picture, Literally, of what it is that you're up against. With the pin(s) that is.
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Old 19-03-2016, 23:46   #10
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Re: Removing Masthead Sheaves

You just need to hit them harder. The only thing holding them on at this point is aluminum oxide and they will come off. They may bend, but they are easy to bend back.
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Old 20-03-2016, 08:22   #11
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Re: Removing Masthead Sheaves

Tsell,
Do you have access through your masthead cap? If it is removable, you can add penetrating oil from both the inside and outside. Good luck and safe sailing.
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Old 20-03-2016, 09:23   #12
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Re: Removing Masthead Sheaves

First I'd protect the surface of the mast while working - it's already marked up a little bit.
Cut rectangular holes to fit around the plates from 2 sheets cut from big Coke bottles & tape them in place. Coke bottle plastic is thin and tough.

With two crescent wrenches I'd try turning the plates as you would a nut seized on a bolt. Twist both ways a little at a time & hope eventually it starts to free off.
Any penetrating fluid you can get in there has more chance of helping with time and raised temperature.

If one plate is welded to the pin the other plate may have a sleeve welded on its reverse side which the pin fits into - that would probably seize.

Lots of options but wiggling them back & forth with wrenches is the least destructive first attempt. Just a mm or two each way or a corner will dig into the mast surface and leave a mark.

Next least destructive would be vibration from an air chisel with a blunt end.
Another piece of stainless between the chisel and your plate to protect it and the mast.
Got to let the vibration do the work, no weight on the chisel at all - that could damage the mast.
Thick gloves to avoid vibration white finger, or pay somebody else to do it.

Lots of other options with drills, saws, heat, welding etc. but more destructive.
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Old 20-03-2016, 15:27   #13
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Re: Removing Masthead Sheaves

Unfortunately, I do not have acces through the masthead cap, it is solid. Great suggestion to make plastic covers to protect the mast, I don't want to mark it up more than it already is.

I had to leave town for work,so won't be able to try to get them out until I get back home next week. Luckily the boat is in the yard, making it easy to spend a little time each day working on it.
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Old 30-03-2016, 17:52   #14
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Re: Removing Masthead Sheaves- Update

Well, thanks everyone, I got the pins out. One of them came out quite easily using an open end wrench to twist the cover and welded pin back and forth. The other one was not as cooperative, and trying to twist it just broke the cover plate off the end of the pin. I drilled a hole in the pin, using progressively bigger bits until I could tap it for a 1/4 x 20 bolt, which I then used to twist that on out.

New sheaves and pins on order from Zephyrworks.
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Old 31-03-2016, 01:15   #15
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Re: Removing Masthead Sheaves

tsell, glad to hear of a successful outcome: well done! And slather those pins with lanolin or Tefgel when you replace them!

Jim
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