questioning my sanity!

Discussion in 'Boat Design' started by Bod, Nov 19, 2015.

  1. fredrosse
    Joined: Jan 2005
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    Location: Philadelphia PA

    fredrosse USACE Steam

    Steel hull, repairs are relatively easy, provided the basic structure is in good shape. The marine survey is a must!. Ultrasonic steel thickness gauges can be bought new for about $50.

    Beyond that, and assuming the hull plates and frames are OK thickness, then a serious sandblasting project is needed to clear all the surfaces (at least below the waterline) down to bare steel. At that point there are many reliable coating systems that, IFF applied correctly, can give many years of service.

    Please forgive the use of a mathematical term in this reply, but it is appropriate here.
     
  2. Bod
    Joined: Aug 2012
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    Location: Leicester

    Bod Junior Member

    Miraculously understood the maths reference :)
    im informed the orginal paint was done properly and looks good on the outside, but the cranelift will tell the full story.... iv not budgetted for shotblasting but I want peace of mind under the waterline and a proper job. Is there a cheaper more labour intensive alternative to shotblasting? A wire brush attachment on a drill?
     
  3. Rumars
    Joined: Mar 2013
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    Location: Germany

    Rumars Senior Member

    A needle scaler would work. Wire brush only massages the rust. Sandblast if you can.
     
  4. fredrosse
    Joined: Jan 2005
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    Location: Philadelphia PA

    fredrosse USACE Steam

    Sandblasting

    This is not so expensive, you just need a compressor, a blasting nozzle, and protective clothing/mask/gloves. Sandblasting to white metal is so much better than any other option. It gets right down to the root of welds, where scaling devices, as well as rotary sanding/grinding wheels will usually leave some old paint and rust.
     
  5. kapnD
    Joined: Jan 2003
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    Location: hawaii, usa

    kapnD Senior Member

    Even sandblasting will not get all the rust off. The problem lies between the plating and the structural members, and all interface and inaccessible areas.
    Your best tool at this point is still a careful assessment of the reality of ever getting rid of the rust.
    There are plenty of derelict FRP hulls laying around!
     
  6. Bod
    Joined: Aug 2012
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    Location: Leicester

    Bod Junior Member

    ok so im sold on the idea of sandblasting the outside and epoxy paint...

    the inside will be less crucial but more difficult due to nooks and crannies where rust gets trapped. Now im a big fan of rust removal solutions. iv used 2 types- one a rust removal gel that makes the rust flake off and the other turns the rust black. both leave no rust and have worked brilliantly in my own experience.... a few have critisiced this as an idea but didnt back it up with anything, so why not?! as part of the method after mechanical means have done there bit... is there any reason why this wont work on a boat? im all ears :) :)
     
  7. kerosene
    Joined: Jul 2006
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    Location: finland

    kerosene Senior Member

    why is the inside less crucial?

    The stuff often used for rust treatments (like evaporust and many others) are basically phosphoric acid if I recall right.
     

  8. Bod
    Joined: Aug 2012
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    Location: Leicester

    Bod Junior Member

    The outside is exposed to the elements, salt, water, scrapes ect...

    The inside is exposed to none of these and will be sealed and insulated from condensation...
     
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