Plating over a steel hull

Discussion in 'Metal Boat Building' started by ljw, May 25, 2007.

  1. ljw
    Joined: May 2007
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    Location: wawa, on

    ljw New Member

    I have a 54 foot 1938 tugboat with pin holes in several places and the remainder of the plating is thin. I am thinking of covering the existing steel with new plating but I am concerned about moisture getting between the plates and rusting out the hull from between. Have any of you had experience doing this and any advice to share? I also wonder if I do this how it may affect the performance of the boat, ie: fuel consumption and speed (go from 8mph to 4??) Thanks, ljw
  2. timgoz
    Joined: Jul 2006
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    Location: SW PA USA

    timgoz Senior Member


    Your concern about both miosture & weight are well founded. Plate over plate is a bad idea. Usually the bad section(s) are cut out and new plate of the same thickness inset.

    To plate over the whole boat would add severally to the weight. Could be catastrophic. I'd consult an NA.

    Good Luck.

  3. Bergalia
    Joined: Aug 2005
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    Location: NSW Australia

    Bergalia Senior Member

    Unfortunately Tim is right. It seems, LJW, you've bought yourself a heap of trouble - expensive trouble. But there are several qualified restoration members who may well weigh in with ideas such as a coating material to prolong her life. Otherwise you could be in for a costly rebuild. Welcome to the forum by the way. And don't give up hope....:)
  4. lazeyjack

    lazeyjack Guest

    sorry mate overplating is not an option, depending on what you paid, seems Bergs is right , you may be better to start agin, judging by your post, you have no experience of steel boatbuilding, so, ripping off plating and replating is hard work, and tricky, old that boat, are you in Canada?, becuz in those years leading up to the ww2, there was a lot of demands on steel, and a lot of poor stuff was produced, In Germany you see fine older boats, tug, barges, and in FR AND Netherlands, but rare to find something of that vintage anywhere else that is any good, Have you some pics to share?
  5. MarkC
    Joined: Oct 2003
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    Location: Germany

    MarkC Senior Member

    Have a look at site and look under 'member boat projects' their is one member 'SteveJ'? who plated over his boat (similar vintage). Plenty of advice there as well.
  6. ljw
    Joined: May 2007
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    Location: wawa, on

    ljw New Member

    I've gone the route of stripping off the old plating and replacing with new. Lots of work but it'll be worth it in the end I believe. I was wondering does anyone know how to trace the history of a commercial boat. I have the previous registration numbers. The boat was made in Erie PA, USA and lived lots of lives over the years. I would appreciate any info. thanks ljw
  7. Bergalia
    Joined: Aug 2005
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    Location: NSW Australia

    Bergalia Senior Member

    ljw - not sure of the system in USA - but in the UK (in my days) Lloyds of London kept a 'shipping register' - and most working boats were listed. There may well be a similar register in your state - or the state of the boat's origin. If you have the registration numbers that will be a great help.
  8. Big H Buck
    Joined: Jan 2008
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    Location: Ontario, Canada

    Big H Buck Junior Member


    Hi ljw

    I live just east of Echo Bay and have a similar problem on my 37'er
    so we could be called neighbors on this site.
    I just now found your thread, and am wondering how your project is going

    I bought my steel boat from a fella in Wawa last March.
    I found the history of my boat through Transport Canada. It is a
    Registered Vessel and was built in 1958. I am owner # 7.

    If your boat was ever registered in Canada, T.C. will have a record of it.
    You can contact them at 1-877-242-8770. 1,2,3.

    I would like to know which path you took in your repairs and how your
    project is proceeding.

  9. Bijit Sarkar
    Joined: Sep 2005
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    Location: Calcutta,India

    Bijit Sarkar Naval Architect

    I do some ship repairs, including patching up riveted hulls, some of which still ply hereabouts.
    What I would do is...
    Get a gauging done. There are agencies doing this. Here they charge about 50cents per point. Get your gauging done for the whole hull, evenly spaced. The areas which are obviously pitted, leave them alone. You need to change them anyway. The areas where plates have corroded to 85% or less of original thickness should be changed.
    Mark the areas you need to replace. place a pastic sheet on top and lift the marking to get the flat plat size.Rememberr to have the corner well rounded, minimum 150-200 mm.
    With thin steel strips/wires ( 3x25 or 5/6 mm rod) bent to shape get the hull curveture at regular intervals.
    Now cut the new plate, and bend it to shape, while checking with your bent strips. If you are careful, you can get an accuracy of 3 to 4 mm this way.
    Once this plate is ready, place it against the hull and mark again. Now release the plate from inside frames by gas cutting ( be careful of oily areas).Cut the plate out and use a grinder to get a smooth edge.
    Now place the new plate, wedge it into place from all sides and make sure you have a gap of 2 to 3 mm all round between old and new plates.
    Tack it into position, hammer it in shape if needed.
    Tack with the internal frames. then weld them.
    Weld the butts from inside first. Do not weld in one run. Do the corners , get to the middles, stagger and rotate your weld runs. That way you reduce distortions.
    Once finished , with a chisel, or a grinder, gauge the weld from outside. You may want to do some dye-penetration tests at this stage. Weld outside following the weld pattern. Paint all welding quickly before they form rust.

    One FRP builder friend of mine challenged me that he could repair the boat of such damaged conditions by coating it with resin putty and glass cloth ( CSM and WR) and he would stand guarantee for 5 to six years.
    I talked to the local ship surveyor. He says why not if he can ensure correct adhesion of resin to steel. The steel has to be shot blasted very clean, I guess. You could try that as an experiment. Should not increase the boat weight much. However, it's still a second choice after renewal.
  10. Brent Swain
    Joined: Mar 2002
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    Location: British Columbia

    Brent Swain Member

    I don't think plating over old plate will save you any time or money over simply removing the plate a bit at a time and replacing it as you go.
    I friend plated over old steel and had his proccess approved by a surveyor. With the surveyor's approval in hand he has been trying to sell the boat for what he has into it for 6 years now with no bites.

  11. welder/fitter
    Joined: Jun 2008
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    Location: Vancouver

    welder/fitter Senior Member

    "List of ships"

    If the vessel was ever registered in Canada, you can find the history on the coast guard website. I don't know if the U.S. coast guard has a similar site, but you could check. In fact, as this publication is worldwide, why not check the Canadian site, you might find it listed & the past names, owners, builders, etc., are also listed. As well, you may be able to find it by entering the reg. number into your search engine. I found info on a friend's ship that way.
    Mike G.
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