Best Lubricant for Rudder post

Discussion in 'Boatbuilding' started by Charly, Jul 31, 2015.

  1. Charly
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    Charly Senior Member

    My rudders go through some hand laid bushings out of epoxy and graphite mixed, that were wrapped around the pipe when the rudders were built. The idea is that the graphite should lube it. Mine are pretty tight in there, and I was thinking I might need to grease them up for less effort when turning.

    My question: is Petroleum base grease OK to use? Is there any kind of grease that should not be used? Posts are 316 SS. Bushing layup is 10 oz cloth and epoxy with contact surface mixed resin and graphite powder.

    THanks
     
  2. Jamie Kennedy
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    Jamie Kennedy Senior Member

    Interesting. Maybe a homemade mix of Vaseline and graphite powder.
     
  3. sdowney717
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    sdowney717 Senior Member

    I would probably use some moly auto chassis grease.
    Did the epoxy absorb water and swell up?
    SS and graphite are fine together.
     
  4. Charlyipad
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    Charlyipad Senior Member


    I don't know, could be. They are kick-up rudders though, so they dry out, when not in use, and they are still a little stiff, after nine months and several hundred miles. When I did the lay-up I put a couple of sheets of wax paper over the pipe, but I still almost couldn't get it off. I finally had to hook the pickup truck to it:D I didn't want any slop.

    last boat ride I squirted some joy on it just to see. I couldn't tell any difference. I am just worried about the chemistry of petroleum and epoxy, which I know very little about.

    I will google moly auto chassis grease thanks.
     
  5. PAR
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    PAR Yacht Designer/Builder

    Epoxy stands up well to the usual lubrication suspects, including petroleum. What you really need is a bushing of UHMPE, which is self lubricating. Tap out for a zerk and pump in some heavy grease.
     
  6. SukiSolo
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    SukiSolo Senior Member

    Along with PAR's suggestion, acetal (Delrin is a common brand) is a good bushing material. Be aware that drilling long holes in it does get some 'springback' in the material so it can end up unintentionally tapered, sometimes a parallel reamer is required to get a true hole.

    One other short term 'lubricant' is a couple of coats of a release wax especially carnauba based ones. These are 'dry' and unlike a real grease do not attract sand, salt and other dirt into the mix creating more abrasion.
     
  7. PAR
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    PAR Yacht Designer/Builder

    They do sell some dry lubricants and the teflon based ones work well, but these dry lubes, including the waxes tend to wash off pretty easily.

    There are a number of these high density plastics available, most a derivative of polyethylene. Lots of acronym laden prospects: UHMWPE, UHMW, HMPE, HPPE just to name a few. Each have a few "brand" names like Dyneema and Spectra. Polyacetal is another form of these (POM) and this is what Delrin is.

    Bushings of these plastics work better in many regards for what you need.
     
  8. Charlyipad
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    Charlyipad Senior Member

    Thanks guys for the input.

    The bearings are integral to the cassettes, so replacing them means rebuilding the whole shebang. The problem isn't big enough to justify that. I just didn't want to degrade anything chemically. If petroleum is Ok then I have plenty of options there to try.

    I did make the thrust bearings (I guess thats what you call them- those washers that separate the tiller heads from contacting the top part of the cassette where they bear down by force of gravity) by cutting up a commercial kitchen cutting board with my hole saw. They are working great. I have found several other good uses for this material.
     
  9. PAR
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    PAR Yacht Designer/Builder

    Cutting boards are a favorite of mine and I've stolen a couple from the other half. These are typically HDPE which is less dense than UHMW, but still self lubricating and make good modest load bearings and bushings.
     
  10. AndySGray
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    AndySGray Senior Member

    The SS may not be as 'mechanically' smooth as you imagine - a light polish to remove high spots might work wonders too.
     
  11. sdowney717
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    sdowney717 Senior Member

    If it is really tight, then how about using a grinding paste to loosen the fit?
    Lap the parts together. the epoxy will yield before the SS.
    Although if you cant get the parts separated to get the paste into the space or rinse it out... dont bother.

    Maybe a grease fitting to pump grease in could help with maintenance.
     
  12. Charlyipad
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    Charlyipad Senior Member

    No, its not that tight. I can pull the post out easy enough. Its just that when I laid up the bushings I left a very close tolerance, thinking that it would be better to have it too tight since is would probably abrade over time.

    The rudders turn OK, I just want them to turn a little easier. I have this rube goldberg steering setup and just trying to eliminate as much friction at each contact point as I can.

    I like the idea of buffing -that would probably do a lot of good, since the pipe was just stock schedule 80 SS. Next time, I would do it different...
     
  13. JSL
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    JSL Senior Member

    On the galvanic series, graphite is quite noble .. SS less so. Could cause surface pitting on the SS, make it rough, & wear down the bushings.
     
  14. Charlyipad
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    Charlyipad Senior Member

    Wow. Now that's interesting I never even thought of that.

    Anybody have any direct experience with that kind of galvanic action?

    and if that is so, I also have some of the same kind of bushings contacting aluminum pipe at the cassette kick ups and at the tiller post... should be even worse
     

  15. SukiSolo
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    SukiSolo Senior Member

    There is quite a reasonable amount of data on galvanic reaction between steel(s) and carbon (graphite), mainly from research for aircraft uses. Also the racing car fraternity have done some work, and made a few observations. One easy way to minimise or obviate a reaction is to put a layer (or 2) of plain glass in the laminate on the surface contacting the steel.

    It also depends on the steel structure, pearlite/austenite etc and composition. One easy way to remind oneself, is to check the electrical conductivity of the material, now carbon in many forms ie graphene etc is pretty good.... though diamond is poor, but excellent with heat. Carbon masts are pretty good lightning conductors....;)
     
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