Carbon rudder posts

Discussion in 'Materials' started by SeaJay, May 23, 2009.

  1. SeaJay
    Joined: Jun 2007
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    SeaJay Senior Member

    Does anyone know if a carbon rudder stock can be used directly against an UHMWPE bearing, or should a stainless sleeve be attached to the stock? I thought I read somewhere that the SS needed to be used as a wearing surface, but that may have been in conjunction with roller bearings. The SS seems somewhat problematic as I suspect there may be some electrolysis occuring between it and the carbon. Thoughts?
     
  2. apex1

    apex1 Guest

    One thought was : use more acro┬┤s and get more replies!!! Naturally YWNUWIM?
    at the end..............
     
  3. nero
    Joined: Aug 2003
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    nero Senior Member

    You will need a sleeve for a wearing surface. Or you can machine the bearing on to the stock and use a bearing surface in the rudder tube.

    Or maybe someone can say if UHMW-PE can rub against UHMW-PE and survive.
     
  4. mark775

    mark775 Guest

    And no, UHMW cannot ride well against UHMW.
     
  5. SeaJay
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    SeaJay Senior Member

    Mark, Nero, Thanks.

    Apex,

    Ultra High Molecular Weight Polyetheylene
     
  6. Eric Sponberg
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    Eric Sponberg Senior Member

    In my carbon fiber rudder designs, I always specify stainless steel sleeves. This is because, in a composite laminate, the determining factor, really, is the resin, and epoxy resins wear down really fast. You have to have a hard wearing surface. I have had on occasion specified other plastice bearing surfaces to be bonded to the carbon fiber part--the point is, you need a bearing surface on the stock to take the bearing pressure and wear. Do not let the bearing ride directly against the carbon fiber stock.

    Eric
     
  7. apex1

    apex1 Guest

    SeaJay
    thanks, I know that as "High modulus PE"

    Richard
     
  8. SeaJay
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    SeaJay Senior Member

    Thanks Eric,

    Actually, I thought it was one of your articles that had mentioned the SS surface but I couldn't find it again (or was too lazy to continue my search!). What is the best method to attach the SS to the carbon stock? Set screws don't seem like a good idea, but does epoxy or similar (EasiChock http://www.tigerpropellers.com/orca_grease.htm ) provide enough adhearance between the SS and carbon? I saw a couple of rudders where it looked like this was the method used so I guess this is the way it is done.

    Regards,

    Doug
     
  9. Eric Sponberg
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    Eric Sponberg Senior Member

    SeaJay,

    Yes, epoxy is fine for bonding. Sand the mating surfaces first to a good roughness with coarse grit sandpaper before gluing.

    The article you probably saw was "Keels and Rudders: Engineering and Construction" in Professional Boatbuilder #96, Aug/Sep 2005, page72. Here is a link to the on-line digital version: http://www.proboat-digital.com/proboat/200508/

    Eric
     

  10. SeaJay
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    SeaJay Senior Member

    Thanks Eric. I was looking in that particular article but missed the notation in the drawings. That was exactly what I was looking for. SS it is!

    Doug
     
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