Replating Questions

Discussion in 'Metal Boat Building' started by Dave Patterson, May 15, 2010.

  1. Dave Patterson
    Joined: Apr 2010
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    Dave Patterson Junior Member

    I have a 28' steel work boat that needs to have plating replaced. The boat is in very good shape except for the steel approx. 30" on either side of the keel and running the length of the boat. I do not weld but will be enrolling in a night school class at a nearby community college. I have been reading everything I can get my hands on to try and get myself up to speed on construction techniques. This website has been great as well as a number of books recommended by other members! I would like to start removing the old plating and am looking for some advice. I don't have a torch or a plasma cutter nor would I feel comfortable using one. Can I use a reciprocating saw to cut the old hull plating as close to the longitudinals and the frames as I can and remove the steel in small sections? I thought I could then use a grinder to remove any remaining material. Is this a good plan or can someone suggest a better approach?
    Also, I will need a welder. I've been thinking about purchasing either a Hobart Stickmate ac/dc or the equivalent Lincoln. From what I am reading, the dc capability is a plus when welding thinner materials. I will be doing all work outdoors so a mig seems like a poor choice. Any suggestions?

  2. hoytedow
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    hoytedow Carbon Based Life Form

    Unplug when it rains?
  3. hoytedow
    Joined: Sep 2009
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    hoytedow Carbon Based Life Form

    Seriously, build a little welder's cart so that you can move it indoors during inclement weather. Shipbuilders have been welding outdoors since the beginning of modern times.
  4. Dave Patterson
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    Dave Patterson Junior Member

    By 'working outdoors' I was referring to wind and shielding gas and not my inability to move a welder into my shop 30' away. Seriously
  5. hoytedow
    Joined: Sep 2009
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    hoytedow Carbon Based Life Form

    Sorry about that. I have found that reciprocating saws are more uncomfortable after extended periods of cutting. Have you any inclination to put a metal cutting blade in a circular saw? Pre-drill alignment holes from backside and mark saw side with crayon or chalk. Straight lines only, of course. Just a thought.
  6. apex1

    apex1 Guest

    I see no advantage in avoiding the torch or plasma cutter.

    Cutting by saw or disc, is more cost and effort and the induced heat can be the same.

  7. Berty
    Joined: Jun 2009
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    Berty Junior Member


    Have a look into using a 7" or 9" angle grinder with 1mm thick cutting discs. It could save you alot of dosh.

  8. SamSam
    Joined: Feb 2005
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    SamSam Senior Member

    Go over to any of the marinas on the Mississippi that have houseboats and ask them who does replating and then get advice from them. Most of the older boats are steel and it's a fairly common thing to have to have done. You might even want to get estimates. Unless you have help and equipment/tools, it's heavy stuff to maneuver around, especially overhead. And then you have overhead welding which is very much not the easiest.

    Most of the people who do it will be portable, as in generator/welder on a truck with tools, a lot of them will be one person operations. Maybe you can work something out with being their "help", getting materials, flexible schedule maybe, as in not in a gigantic marina spring rush hurry. No matter what, you'll find out how people go about it, where to get materials and other advice.
  9. scott hightower
    Joined: Jul 2010
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    scott hightower Junior Member

    Welding Outdoors

    Welding outdoors is OK but don't do it on a windy day. If it it is too windy the breeze will blow away your sheilding gas and you will end up with porosity in the weld.

    Another option is to use flux core MIG wire.

    Fab Manager
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  10. gonzo
    Joined: Aug 2002
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    gonzo Senior Member

    A MiG with flux wire works fine outdoors regardless of wind. You can fill gaps much easier, specially if you are just learning to weld. There is less likelihood of burnig through and making holes in the plating too.
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  11. welder/fitter
    Joined: Jun 2008
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    welder/fitter Senior Member

    Gonzo, I'm confused by this. Because you're suggesting that Dave doesn't need to worry about wind, at all, I'm guessing that you're suggesting he use self-shielding wire? But, in the first sentence you suggest GMAW("MIG") w/ flux-cored wire? All confusion aside, If you are referring to FCAW-SS, that might be a bit of a challenge for a guy who is going to take a welding course, as it has been my experience that self-shielding wire has a pretty narrow "sweet spot" & can be a challenge for welders whom have more experience. Personally, I figure that, as these welds are below the waterline, it might be more prudent for Dave to do the fit & tack, with SMAW(stick), and have a pro do the final welding with whatever process is available. I may have misunderstood your post, however, and look forward to getting a better handle on what you're suggesting.
  12. Ad Hoc
    Joined: Oct 2008
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    Ad Hoc Naval Architect

    It is usual practice to weld the first run from inside the boat when in tricky conditions. Thus the enviornment is more controlled. Then back gouge and do the second run 'outside'...assuming the root has good fusion.

    Then, if you are a stickler for QA...dye-pen the root before you seal outside.

  13. Wynand N
    Joined: Oct 2004
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    Wynand N Retired Steelboatbuilder

    Exactly the way I had built all my steel boats in the past - regardless of the conditions.
    I usually back gouge from the outside with an angle grinder until the blade shows solid steel and then laid down the filler/cap run. Then again, I had built 90% of all my boats upside down which makes the back grinding much easier (safer) and most outside welds in a down hand condition.
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