aluminum Hull repaired issue

Discussion in 'Metal Boat Building' started by Brian.Lin, Jun 28, 2018.

  1. Brian.Lin
    Joined: Aug 2006
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    Brian.Lin Junior Member

    dear all,
    we found small crack(abt. 5~10cm) in way of bottom hull.
    kindly refer to attached photos.

    we intend to use stop hole to carry out the repaired job.
    but, we can't find any document to support us.
    kindly provide us your professional suggestion.
     

    Attached Files:

  2. rwatson
    Joined: Aug 2007
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    rwatson Senior Member

    Just from memory, isn't this process where you insert pins and bolts and joiners, and grind them down ?

    That would work well on heavy gauge aluminium like engine blocks etc, but for 4-6 mm plate, , it sounds like a bad idea, as the amount of metal to grab would be pretty small.

    For the bottom of a boat with flexing, potentially high pressure, grinding the crack out and welding would be the only way I would treat it.

    The other issue is, what caused the crack ? If it is an area prone to flex and pressure, you would be advised to weld it thicker and longer to provide some obviously needed extra strength in that area.
     
  3. Brian.Lin
    Joined: Aug 2006
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    Brian.Lin Junior Member

    Dear rwatson,

    thx for your opinion.

    end holes are stopped hole, we also use grinder/welding the crack.

    our strategy is as follows.
    1.grinder the crack position and clean the surface
    2.identify the tip of the fracture(PT)
    3.decide size and location of stop-drilling
    4.Drill Hole
    5.gauging both sides of the crack and clean the surface.
    6.filling the hole by welding
    7.welding the crack seam.
    8.Verify by PT
     
  4. Barry
    Joined: Mar 2002
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    Barry Senior Member


    Are you able to get access to weld both sides of the crack

    And you are not clear on 1. grind the crack position, the crack should be ground to make a V about 1/2 way through, from the side that you are first welding.
    then the backside of the weld opened up with zip cut blade to sound weld and the opposite side welded to complete

    If access allows, and the crack is horizontal put the V on the side that you will down hand weld, back cut and finish overhead on the second, if that is the orientation
     
  5. rwatson
    Joined: Aug 2007
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    rwatson Senior Member

    That sounds like a good plan.

    I thought you were referring to "stop hole", the commercial product.

    It sounds like you have thought it through very carefully, and that should work fine.
     
  6. Brian.Lin
    Joined: Aug 2006
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    Location: TW

    Brian.Lin Junior Member

    dear Barry and rwatson,

    thx for your comments.

    do you have any document to state the repaired job as this?

    if the vessel is registered as classification society, the surveyor will ask us to renew the plate (min. 300mmx300mm).-follow IACS No.47

    they can't accept the method as we discussions.
    their opinion is there is no rule/document can support this way.
     

  7. Ad Hoc
    Joined: Oct 2008
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    Ad Hoc Naval Architect

    Need to establish why it cracked first - otherwise any repair will most like follow the same fate.
     
    Brian.Lin and rwatson like this.
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