Regarding Aluminum stern tube

Discussion in 'Boat Design' started by Hunterr, Jan 18, 2017.

  1. Hunterr
    Joined: Jun 2015
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    Hunterr Junior Member

    We are korean Aluminum Shipyard 'Daoyachts'

    Is it possible to make aluminum sterntube?

    actually, we are used to using SUS sterntube -Choke paste-Al tube.

    THE MODEL : http://blog.naver.com/tvgram/220901977400
     
    Last edited: Jan 22, 2017
  2. gonzo
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    gonzo Senior Member

    Sure, many aluminum hulls use aluminum sterntubes. Are you referring to where the rudder post comes into the hull?
     
  3. Ad Hoc
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    Ad Hoc Naval Architect

    Just make sure you use 5083-0 grade and not 6082/6061 grades
     
  4. baeckmo
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    baeckmo Hydrodynamics

    ......and that the position where the cutless bearing is placed, has direct support from the hull structure (i.e. not in a cantilever, or overhung position). This with regard to the relatively low fatigue strength in aluminium.
     
  5. Hunterr
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    Hunterr Junior Member

  6. Tigawave
    Joined: Sep 2007
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    Tigawave Junior Member

    Aluminium bearing carriers

    Yep, many Aluminium boats have Al bearing carriers whether stern tube or P bracket / strut. Some bearing suppliers size the bearings for a glue/epoxy fit of the bearings which has benefits for an Al carrier. From Australia Maritex do many bearings for Al vessels.
     
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  7. JKboat
    Joined: Nov 2020
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    JKboat New Member

    Wondering whether we insert the bearing directly into aluminium stern tube or use an ss316 sleeve between the bearing and the stern tube? Any advice would be greatly appreciated.
     
  8. BMcF
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    BMcF Senior Member

    Using a 316 sleeve sounds like a recipe for trouble. I've seen examples of stainless sleeves in aluminum become smaller in diameter as the powerful galvanic interaction between the aluminum and SS grows thicker. Small marine waterjet pumps are a good example of that...I've had to scrap a few because the stainless inner sleeve had been "collapsed" enough by the corrosion that it caused the jet impeller to seize
     
  9. JKboat
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    JKboat New Member

    Thanks for the reply, but the galvanic corrosion between ss and aluminum always eats aluminum, as it has a higher tendency to give away electrons than SS. According to corrosion experts, the SS becomes thicker and aluminum becomes weaker in this process. What could be the reason for the collapse of the SS sleeve ?, Maybe impurities in the metal, don't know. Any advice or thoughts, please.
     
  10. baeckmo
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    baeckmo Hydrodynamics

    There are corrosion products "growing" in the contact area. They increase the pressure around the periphery of the sleeve, which finally collapses inwards along a generating line.
     
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  11. JKboat
    Joined: Nov 2020
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    JKboat New Member

    Thank you baeckmo and BMcF for your guidance.
     
    BMcF likes this.
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