Help with replating options

Discussion in 'Metal Boat Building' started by Salmoneyes, Sep 9, 2018.

  1. Salmoneyes
    Joined: Sep 2018
    Posts: 89
    Likes: 1, Points: 8
    Location: Southern Oregon

    Salmoneyes Junior Member

    I will attempt to keep it simple and to the point

    I am completely rebuilding a 12m steel pilothouse ketch and I have her stripped to the bare hull (except main engine and genie which is next)

    Hull is built from 4mm Core Ten, using no stringers. The ribs are 2x2x 1/8 inch T-bar, spaced 36 inches and appear to be added after the fact. The pilothouse is amidship with 4mm steel bulkheads and floor. There are two 150 gallon SS tanks welded in up front that I believe contribute to its hull strength.

    Typical electrolysis corrosion at water line. Plan is to weld up the deeper ones and fill the remainder with Belzona XL.

    There are some areas where sea water was trapped and caused corrosion which I would like to replate. It's not as bad as I had expected by any means, but we plan to spend at least the next ten years cruising and for piece of mind, I just want to get her perfect.

    I believe that the construction process was critical to accomplishing the strength required, and I am aware that cutting and welding can potentially have adverse effects. I can do my cutting with a cut off wheel to prevent heat distortion from torching. The question is welding.

    I am willing to buy whatever is best for this project. I have been welding non professionally since the 70s, with gas welding being the first medium. I also used ARC until I got my first wire feed. I have a little experience with TIG which quickly became my favorite.

    The boat is outside so shielding gas is an issue that would need addressed. I have been reading about the DC inverter stick welders but have no experience with one. I keep thinking that gas welding with controlled heat would be my best bet, but really want to get some opinions on this...

    Again, if I do not have what I need, I will purchase it, (within reason) so I am open to all the advice and recommendations.
    Thank you in advance....

  2. John mc b
    Joined: Nov 2018
    Posts: 5
    Likes: 2, Points: 3
    Location: UK and Spain

    John mc b Junior Member

    Hi, I am shipbuilder by trade, first off forget about gas welding, too much heat, use a stick, just practice for a while and you will be OK, weld inside first everywhere and then background outside an weld, the hard bit is to determine where you need to replate, take a very small hammer and tap the plate all over, after a while your ear will tune to the good and bad, without looking at the boat in great detail, it is hard to give you enough advice, if you are going sailing for long trips you have to get this right. I would love to check it over for you, there are lots of things I can tell you but I would need to know more. Also I would not recommend using Belzona on the waterline, I would replate over the bad area or cut it out and replace, there are a couple of ways to do this
    Salmoneyes likes this.
  3. Barry
    Joined: Mar 2002
    Posts: 1,794
    Likes: 456, Points: 83, Legacy Rep: 158

    Barry Senior Member

    I would use a wire feed but as you have identified, you will need to shield the welding in windy conditions. If you went with a spool gun or a standard mig set up, you can get a 6 or 8 inch flexible tip which makes it possible to get into tight places. You can get steel wire down to at least .030 maybe smaller for thin metal. Another advantage is that you can get say a 30 foot connection between the welding machine and the spool gun to make it a little easier to use. If you have a lot of welding to do, then the standard mig set up will work. As John just stated, forget about gas welding,
    tig, too much heat and distortion
    Salmoneyes likes this.

  4. gonzo
    Joined: Aug 2002
    Posts: 16,576
    Likes: 1,560, Points: 123, Legacy Rep: 2031
    Location: Milwaukee, WI

    gonzo Senior Member

    If you are wire welding outside, use flux wire since it does not need gas. However, stick welding is cheaper and faster.
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.