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aluminum hull plating pitting

Discussion in 'General Yachting Discussion' started by 993RSR, Nov 15, 2024 at 2:43 PM.

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  1. 993RSR, Nov 15, 2024 at 2:43 PM
    #1
    993RSR

    993RSR Senior Member

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    What is the formula, if any, for acceptable amount of hull plates interior pitting? Inspecting the interior of the bottom plates (bilge) some areas have pimple size pitting mostly 1/8" or less deep and wide. The largest pit was 1/4" wide and 3/16" deep.
    Is the severity based on the thickness of the plating?
  2. DOCKMASTER, Nov 15, 2024 at 7:27 PM
    #2
    DOCKMASTER

    DOCKMASTER Senior Member

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    ‘In the commercial world it is based on % of loss from original thickness. Anything more than 25% loss in thickness and regulatory bodies will make you replace it. In the case of pitting as you describe you can measure the depth of pits and average the depth to get a loss % over a few square feet. What is the original plate thickness? If you have 3/16” deep pits that doesn’t sound good unless you have unusually thick hull plating.
  3. 993RSR, Nov 15, 2024 at 7:43 PM
    #3
    993RSR

    993RSR Senior Member

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    Location:
    Annapolis/ Palm Harbor
    Thanks for the data point. A surveyor mentioned the 25% to stay in class.
  4. Capt Ralph, Nov 15, 2024 at 8:08 PM
    #4
    Capt Ralph

    Capt Ralph Senior Member

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    Who is measuring the pit depth, plate thickness and area size?
    Guessing by finger touch or real devices?
    Audio or acoustic measurements are really needed here. A surveyor or tech that knows how to really use the equipment is needed also.

    I have witnessed a few false alarms by overnight surveyors.
    In the past on a Striker and Roamer I had worked on, Surveyors had caused false alarms when they found blems/pits in the surface fairing.
    On another Roamer, we thought the fancy equipment was working and still reported bad plates. Again the strange micro balloons fairing was messing up the readings.

    So, before you call out the plasma cutters and order material, really make sure you really have a problem.