Grounding a steel hull

Discussion in 'Metal Boat Building' started by LochanOra, Feb 5, 2019.

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  1. LochanOra
    Joined: Feb 2019
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    LochanOra Junior Member

    Hello, embarrassing noob question incoming! Also I’ve searched the forum for this topic, but I apologise if this has come up before. Maybe it’s just that dumb a question!

    Firstly it’s great to find a forum dedicated to metal boat building, this will not be the last silly question I post!

    I have a 35 foot steel boat, which has some deck rust underneath the teak (which was screwed down with stainless screws argh! It’s an ex demonstration yacht).

    I’ve now taken two welding courses, focusing on stick welding - as I’ve been told by my tutor that with stick ‘if it looks good it is good’ - and my beads are starting to look half decent. I’m going to start by welding up some screw holes, but my silly question is: where and how do all you expect welders attach your ground lead?? And is it ok to have current passing through the entire hull? Is it prudent to disconnect electrical systems etc?

    My own thought was to grind some paint off the edge of a cockpit locker and attach the ground lead there?

    Many thanks for any help in advance, thrilled to have found such a treasure trove of info.
     
  2. JamesG123
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    JamesG123 Senior Member

    where and how do all you expect welders attach your ground lead?

    As close to the work as you can get.

    And is it ok to have current passing through the entire hull?

    Not really. Can you? Usually. But...

    Is it prudent to disconnect electrical systems etc?

    Yes.
     
  3. LochanOra
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    LochanOra Junior Member

    Thanks JamesG, much appreciated. Do I need to go beyond just unplugging instruments and transducers etc?
     
  4. JamesG123
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    JamesG123 Senior Member

    It depends on the gear and how they are mounted. If you are sure they are insulated from the hull with rubber/plastic mountings then it should be fine. Don't forget the engine electrics. You can burn up an ignition system just as fast as an electronic gadget with a stray highvoltage flux. Another reason to put the ground clamp as close to what you are working on as you can.
     
  5. LochanOra
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    LochanOra Junior Member

    Thanks very much, really appreciate the advice. Not sure I would have thought to disconnect engine!
     
  6. Blueknarr
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    Blueknarr Senior Member

    Magnets can hold ground to flat steel.
     
  7. LochanOra
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    LochanOra Junior Member

    Great solution! Thanks very much
     
  8. M&M Ovenden
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    M&M Ovenden Senior Member

    Hi,
    As others have said, the return clamp as close as possible to the work, but be practical. This is also a good time to make sure your entire electrical system is isolated from the hull - ideally you will only have a single bond to the hull that you can remove while welding. You should be able to weld on the hull without damaging any equipment if there is no other reference point (shore power), but really disconnecting everything shouldn't take long so it's not worth the risk.

    Cheers,
    Mark
     
  9. LochanOra
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    LochanOra Junior Member

    Cheers Mark, about to get into it this weekend!
     
  10. Barry
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    Barry Senior Member

    Storing and Re-drying Electrodes | Lincoln Electric Canada https://www.lincolnelectric.com/en-ca/support/welding-how-to/Pages/storing-electrodes-detail.aspx
    Many welders, even experienced ones, often store their rods loose in the atmosphere. Once you get an arc, the instant heat through the rod will drive out moisture pretty quick on a sustained pass.

    With stick welding you need to follow the above storage and drying for welding rods. While some of the discourse contained in the article mentions quality of weld, another often overlooked
    aspect is that moist shielding flux coating will often break off when you are attempting to strike the arc, resulting in a random weld arc direction. Additionally, when the coating sluffs off due to it being "punky" due to moisture pick up, you will often stick the electrode to the metal underneath. Especially at the lower amp/voltage that you will be using to weld up small screw holes.

    So unhook the positive and negative side of any battery, unhook the engine to hull grounding wire, and any other corrosion protection wire that may have been hooked to rudder posts, any
    through hulls etc.
    I would purchase an anti zap tool, probably 70 US bucks and hook it between the positive and negative leads that you have taken off the batteries.

    When you inadvertently stick the rod to the hull, and you probably will at low V and Amps, the hull is in essence shorted to the welder and you will easily be able to jump a 1/4 inch gap to any
    wire, instrument that will be close to a grounding opportunity.

    If the thickness of the deck is about say 3/16 ths of an inch you could do the welding with a torch but in thin materials you could run into distortion.

    I would instead borrow a mig welder, 030 wire, argon/co2 mixture, set the cup quite forward of the tip, ( you will have to play with this) to inhibit shorts when starting the weld arc

    Keep the clamp as close as you can to the work and ensure a solid ground, not just laying the clamp on bare metal.

    Note also that while the hull is not supposed to be the completion of the circuit in a metal boat, but a ground wire is necessary back to a dedicated ground bus, hooked to the neg side of the battery for each circuit, there does not appear to be absolute rules that state that the equipment cannot be attached to the metal hull along with the required dedicated ground wire. (At least I could not find this in the ABYC manual??) (I am referring to a comment that the equipment installed in a metal boat is isolated completely from the hull

    With the potential of an arc presenting itself in a piece of equipment when you "stick" a rod to the hull with a poor start of an arc, you really have to be careful

    If you have any fuse/circuit breakers switches in the system, shut them off or pull the fuses to even further mitigate risk
     
    Last edited: Feb 8, 2019
  11. LochanOra
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    LochanOra Junior Member

    Lots to think about there Barry thanks very much.

    When you say ‘not supposed to be used as completion’, you mean it’s inadvisable? From your explanation I can see why, but also it seems like the risk of arcing onto something other than the work piece could be mitigated a lot (by ensuring nothing to arc to)? From what I’d read and people I’ve spoken to, it seems like people do it?

    I also don’t know about ground buses - would you happen to know of any good online resources? The reason I’m asking on this forum (glad I did) is I couldn’t find any surprisingly.
     
  12. Barry
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    Barry Senior Member


    ABYC 12 volt DC requirements state that any equipment will have a power line running to it and a dedicated line back to a formalized ground that is attached to the negative side of a battery.
    Rather than run a hundred small gauge wires back to the negative post, it is easiest to bring a large ground (or positive) wire up to a termination block/busbar which has one large wire from the battery and then attach a quantity of smaller gauge wires to it
    [​IMG]
    For a fibreglass boat (as fibreglass does not conduct electricity) it is physically essential that you have a dedicated wire back to the negative side of the battery ( through terminal blocks /busbars) just to make it easy. With a metal boat, you could just run a hot to the equipment and take the negative side and hook it to somewhere on the hull to connect to ground. But this can cause corrosion, and in the case of a short, a possible source for a fire.
     
  13. JeffreyWH
    Joined: Feb 2019
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    JeffreyWH New Member

    Hello M&M
    This is my first question as a newbie.I am having sleepless night from reading to many Q&A's about ferro boats. When welding on a steel boat would it make a difference whether you put the boat up on a hard stand weld and ground the boat to earth with a separate M.E.N to ground as power lines are?...Jeffrey
     
  14. M&M Ovenden
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    M&M Ovenden Senior Member

    Hi Jeffery,
    I don't really understand your particular scenario , but I assume it means you have a welder connected to one panel with a M.E.N, and the boat is being powered from a separate panel. This is a bit of a strange situation, as I would have expected both would be powered from a panel that is closest to the location. My thoughts in my above comment was that it would allow any equipment to float up or down with the welding supply if needed. When you are welding the "ground" electrode can actually be the positive or negative - depending on welding requirements.

    I can't see how disconnecting ships's equipment could take longer than a few minutes. Battery banks should have a main fuse / circuit breaker (or remove terminals), disconnect shore power and if you have a single ground point disconnect that also. I would do this if I was doing any welding while on shore.

    Cheers,
    Mark
     

  15. Nick.K
    Joined: May 2011
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    Nick.K Senior Member

    We do a lot of this type of repair in the yard where I work. The easiest way to create an earth connection is often to clean a small area of steel close to the repair area and tack on a temporary lug. You can put you foot on the earth clamp against the deck to make the initial earth while you do this. Only weld one side of the lug with a small weld and you'll find it easy to snap off and clean after.

    Assuming that you'll be using a small portable welder, the welder can only short back to itself. In ten years of doing this type of work I haven't yet seen the electrical systems on an boat either being disconnected or damaged during welding work.

    A much greater risk is fire which is quite common. It is very difficult to protect the interior adequately when you are welding up hundreds of these type of holes. Both grinding sparks and weld spatter can cause fires below some distance from where you are welding. It is essential to have extinguishers to hand and very prudent to have someone watching for fire below. I recommend that you grind clean the holes from below as well as above before welding as the burning paint inside is also a fire risk and besides, it leaves a really nasty smell. If you are going to be welding near insulation (or if spatter can drop on to insulation) I strongly recommend that you remove some and do a burn test. I once saw quite new propriety engine sound insulation go up in flames that spread frighteningly fast.

    If the deck is pitted it is likely you won't be able to clean the steel around the holes very well unless you make it a lot thinner. Low amp welding doesn't work well on dirty steel. You may get better results by turning up the amps and doing pulses of weld with one or two seconds between. It takes a bit of practice but you would be less likely to finish with porey welds.
     
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