Need advice on how to fix crack

Discussion in 'Boat Design' started by Ben Madsen, May 18, 2021.

  1. Ben Madsen
    Joined: May 2021
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    Location: South carolina

    Ben Madsen New Member

    I got a crack in my Jon boat. The crack is right above the bow eye right where the bow stop roller makes contact. Since this is in a high-stress area near the bow eye, I would probably like to reinforce it also. Any ideas on the best way of fixing this? thumbnail_IMG_7772.jpeg thumbnail_IMG_7774.jpeg
     
  2. comfisherman
    Joined: Apr 2009
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    Location: Alaska

    comfisherman Senior Member

    Find a gifted tig welder, that's about the only way to fix that thin of aluminum.

    As to a doubler, have the same welder take some flat bar and make an inner and outer doubler that replicates the angle of the bow. Then thru bolt or rivet the inner and outer parts.

    Thin skin aluminum is tough to reinforce as it usually just pushed the issue to the edge of the reinforcement. In this instance its probably just isolated wear due to the trailer stop so should be an easy fix.
     
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  3. messabout
    Joined: Jan 2006
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    Location: Lakeland Fl USA

    messabout Senior Member

    Do what Comfisherman says. Find a competent welder who is experienced with aluminum. go from there. Not a serious problem to fix.
     
  4. Ad Hoc
    Joined: Oct 2008
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    Location: Japan

    Ad Hoc Naval Architect

    You would need to remove the affected area and replace with new plate.
    Then you'll need a rubbing strake over this region - as a sacrificial surface.
    Internally, you may well need some stiffening to support this localised region better too.

    Without dwgs of the internal structure hard to comment further..
     
  5. comfisherman
    Joined: Apr 2009
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    Location: Alaska

    comfisherman Senior Member

    9 outta 10 times it's a wood step up in the bow that can be unscrewed or drilled out and un riveted. Usually a large chunk of stainless round stock is placed behind the affected areas to control over heating. Then a simple tig setup to seal the seam.

    To reinforce it I'd get 2x chunks of some wide flat bar and tac them together matching the v, do a second set on the outside in the same manner. Then through drill on the corners the inner and outer doubler with some sealant and you should be adequately reinforced for some energetic trailer landings.

    If it's a metal bow step, might be time to consider a burly twist out hatch....
     
  6. Kayakmarathon
    Joined: Sep 2014
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    Location: NewEngland

    Kayakmarathon Junior Member

    I would sand some of the pain away, inside and outside. Cut 6 fiberglass patches that cover 2 inches left and right of the crack. Mix a small batch of epoxy resin thickened with fiberglass spheres. Press the putty into the crack. Mix a plain batch of epoxy resin. Place the first layers (inside and outside) at 45 degrees to the crack. Place the second layers normal to the crack. Place the third layer on just like the first layer. Place wax paper over the exposed fiberglass while curing to get a smoother surface that requires less sand of sharp strands.
     

  7. comfisherman
    Joined: Apr 2009
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    Location: Alaska

    comfisherman Senior Member

    Seems like an odd choice for an aluminum boat, maybe the vinylester would stick well enough.
     
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