steel hull restoration

Discussion in 'Materials' started by cptmac, Mar 14, 2014.

  1. cptmac
    Joined: Mar 2014
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    Location: florida

    cptmac New Member

    I just purchased a 24 ft steel ketch which i believe to be 50 years old.i would like to see her through another 50 and plan on restoring her. she was maintained by the previous owner for quite some time but not very professionally. i see rust streaks coming up from under paint in places. there is rust along edges where bulkheads meet the deck. i cannot have her hauled out and must do much of the repairs on the water unfortunately.any suggestions on paint for the inside and outside? where do i start? i understand Ospho is my best friend right now to prevent and slow the rust
     
  2. PAR
    Joined: Nov 2003
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    Location: Eustis, FL

    PAR Yacht Designer/Builder

    Welcome to the forum.

    A steel boat of that age, you just have to have surveyed. The plating can be half the thickness it was designed to be and a host of other issues, many corrosion related. Maybe you can post some pictures, we might be able to ID the old lass and get a clue about her condition.
     
  3. Jacques B.
    Joined: Oct 2013
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    Location: Florida

    Jacques B. Junior Member

    Although the Neeltje was built in 1902 (ten years before the Titanic, but using the same riveted 1/4" iron plate design), she only had her first partial re-plate in the mid-1990s, but was so pock-marked when I bought her last year that a full (up-to-the-waterline) hull re-plate turned out to be the most cost-effective remedy.

    The new 1/4" steel over-plating was hand formed, seamed, and button-welded to the existing hull every 15" on center, so while it was the most "cost-effective" solution, it certainly wasn't a cheap one.

    That got me to thinking that something must have changed over the past 111 years to make a metal hull rot faster in the past 18 years than it had in the previous 93, so I did a little research and learned all about galvanic corrosion as it applies to boats.

    First off, it turns out that the boat had spent most of it's life without any kind of electrical power on board whatsoever, and was only "motorized" (I believe) in the 1980s.

    Secondly, she didn't cruise from one marina to the next and hook-up to shore power until she came to the States about 30 years ago, and thus was never exposed to vagrant electrical currents until then.

    I've since had her equipped with the mother of all galvanic isolators, but only time (and a dozen new 20-lb. zincs) will tell if she's being sufficiently protected.

    Granted, your boat is considerably younger, and may already be equipped with some sort of galvanic protection, but I'd keep an eye on that just the same if I were you.

    Jacques
     
  4. Jacques B.
    Joined: Oct 2013
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    Location: Florida

    Jacques B. Junior Member

    Addendum:

    Rust on a steel boat is like milk on Cheerios, you can't have one without the other. You find it, you scrape it, you paint it. And if you've done it properly, you probably won't have to repaint the same spot for a year or so...:mad:
     

  5. michael pierzga
    Joined: Dec 2008
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    Location: spain

    michael pierzga Senior Member


    Look into surface tolerant industrial paints. The stuff they paint bridges and tanks with.

    The proper way to coat a steel boat is to sandblast then epoxy prime.

    This is impractical for you so grinders, needle guns, chipping hammers and wire brushes are the way to go .

    For rust to form you need moisture...use best craftsmanship whenever attaching a component....watertight. Everything, even interior components. No water allowed.

    For a paint film to act as a water barrier it must be the correct thickness.

    Follow the instructions.....Several thin coats of primer.
     
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