masthead sheaves

[BenM]

The sheaves on my masthead of my new to me CP-16 are lock up.  Neither of them turn at all.  It appears they have been that way for a while because they are worn and are no longer round.  I have contacted hutchins and they suggest I contact dwyer. dwyer has the sheaves and the whole mast head assembly.  I am not sure what the best way to go on the repair.  It would be cheaper to buy the sheaves.  I am not sure why they locked up so I am trying to decide if it is better to replace the whole thing.  Has anyone else had the same problem.

If I replace the sheaves it looks like I have to drill out the pins holding then on and replace them.  The diagram on dwyer website shows clevis pins holding the sheaves on.  Is this the best options? How do I prevent the problem from happening again? 

Thank You.


 

[MacGyver]

Ben,

Salt water or fresh water?

Salt water will cause more of a degradation than the fresh water would. If that is the case, replace the parts.

Fresh water usage typically causes a small amount of seizing due to dissimilar metals, not a big deal. On my 19, I hammered apart the pieces as best I could, then filed the inside sheave hole to better smoothly run on the sleeve, which then had a pin through it. I then used a grease to lube it all up after I was happy with the rolling ability without the grease. Clean the parts off each time before test fitting to one another as grit will cause them to run bad as well.

I think I used like 400 grit...... maybe even 600 on the aluminum as the fit still needs to be snug, just not so snug to not allow grease in it (or a lubricant that will hang around.)

What happens is these parts age with no one taking care of them..... They do require a slight bit of attention now and then, perhaps once a year?

If your sheaves are worn somehow, but by rope or wire, etc, then replace them. This is integral to making raising and lowering the sails easier, so make it as smooth as possible, it will make sailing the boat more enjoyable, trust me.

Mac

[sailen69]

Ben,

I recently ordered replacement sheaves for my 83' CP-16 from Dwyer Mast Co.  I also ordered the pins and rings for the sheaves along with some cheek blocks.  My original masthead sheaves still work well but are showing signs of age from the sun.  I will change mine out this winter or sooner.  I just wanted to have the parts on hand for when I get the time, or if the original sheaves give out.  I can't imagine your sheaves bound up, but things happen.  I would think you should be able to easily change your sheaves as long as you; 1 Will have a clean, round hole for the pin.   2 The inside clearance for the sheaves is good.   3 No damage to the masthead.

As far as grease for your sheaves, and many other things, I would recommend using something like Sailkote.  I have been happy with using it on sheaves, blocks, mast / boom tracks, and just about anything that moves on a sailboat.  It is easy to use and it is a dry lubricant so it will not collect dirt or grime, nor leave greasy oil stains.  I usually wash my boat down and lube things up in the spring when I get my boat out of winter hibernation.

Good luck with your project and good sailing,
Rich

[BenM]

I order the sheaves and pins from dwyer.  The current ones are held in place with rivets.  I will  drill them out, and hopefully everything will work.  The pins and rings will make them easier to pull out in the future. 

thanks for the help.   

[skip1930]

Put the mast down on the ground and remove the cotter pins running through the pins that the sheaves ride on.

Next grab a bottle torch, I like butane. Not propane. Heat red hot and beat out the pin with a drift.

Do the next pin. If this fails spray on your favorite penetrating oil. I like KROLL. Works on my 82 year old Ford, and come back tomorrow.

Take the pin and sand it smooth. Or wire brush on the bench grinder. Or chuck it into a 1/2 drill motor and spin it, one end at a time.

Wire brush the holes in the sheaves with a steel bottle brush, a rolled piece of emery cloth chucked in a drill motor or chase the hole with a drill.

Put it all back together with new cotter pins and slather everything that moves with Permatex Neverseaze.

skip.

[MacGyver]

"Next grab a bottle torch, I like butane. Not propane. Heat red hot and beat out the pin with a drift."

Whoa Skip. Not to be a jerk, but that is not a good idea, Aluminum by nature cannot take much heat and it is brittle. I am not sure how much you have messed with it, but if you take a piece and heat it up, the exterior acts like a bag holding liquid aluminum inside. When the alloy cools back down, the situation is left with a lot of porosity and it is very brittle.

If those pins are SS, the Chromium and Nickle alloys (depending squarely on what exactly is in the mix, and the ratios, etc) take a lot of heat as well, more than enough to make that aluminum mast head toast.

If it was all steel, or several of the steel alloys I would say heat is a friend..... but not with aluminum........ aluminum is a temperamental beast to work with..... hell, you can only weld it maybe 2 times before the crystallization sets in..........

Just my 2 cents.
Some of the other info you give is a good start. But I haven't found a penetrate yet that really did good with aluminum's corrosion which is typically the issue on mast heads.

Mac

[skip1930]

"Aluminum ain't nothing but compressed mud"

Well Mac your right. I had no plans on melting a thing. I misspoke when I said 'Red Hot'. The hotter the flame the less time it takes to warm thing up.

I meant 'get the bugger hot'. We heat the pins and aluminum [the coefficient of expansion for aluminum is 0.24 while steel, doesn't matter if it's black iron or stainless steel, is 0.12. This dissimilar expansion is the magic that is needed to open things up and to expand them. That 'fuzz' around corroded aluminum won't stop movement.

That tiny space created then allows for a drift pin to R&R them or to squirt some P~oil in there if need be.

As far as aluminum hull fitting and tac welding 4, 6, 8, and 10 mm beveled aluminum 6061 T6 and 6018 [?] hull plates between frames, I think the assignment was from frame 17 to frame 27 on this baby here. Both port and starboard.

Although it seams like a small number of plates it took months. Welded aluminum shrinks like a mother. So we measure, Saws-All, jack back out, measure and tac her again. Then the welders come back and shrink her again. We build the boat three times at least. Boat building with aluminium is truly a joy.

No cold tacs! Then it needs to be ground out and re done.

skip.

[Salty19]

I've always used ice when delicate pins, bearings, etc are involved.  Ice will shrink the pin and enlarge holes (they will contract away from an opening).
An old dirt-biker wheel/suspension bearing trick. Put bearing races in the freezer overnight to tap them more easily into the steel/alum frame.

You're going to have get the sheaves off and see what's going on-rust, debris, damage, etc.

This part has evolved a little over time (rivets then pins). You can either drill out the rivets on the sheaves to see what's going on with them-replace or repair as needed, convert them to pins or buy the new assembly.

Could just be a bird has made a nest inside the mast too and sticks are fouling them. When I brought our 19 home it was full of little sticks from an industrious bird preventing operation.

[skip1930]

Shades of Boeing Airliners ... Mystery Metal.

On Marvelous Inventions on the Discovery Channel there was an episode about this metal.
It expands when cooled and contracts at room temperature. Boeing uses it for no heat, no solder hydraulic connections.

And in Japan, it's used because it has a memory and retains a given shape once heated to body temperature for underwires.

skip.

[BenM]

Thanks all.  I drilled out the old pins or rivets or whatever they are called.  Replaced them with clevis pins so I can pull them out easier next time.  There was a lot of crude inside the housing.  I scrapped it all out sanded it down starting with 120 going to 320.  Everything works now.  planing on doing a little driveway sailing today.  Weather is great so I may end up taking it out to the lake.