Mig or Tig

[Paul McCabe]

Hi Guy's

I am currently a non-welder but I have a potential project, houseboat, looming and I need some advice. The boat is in need of some repair and alteration to make it into a pretty decent houseboat. Knowing nothing about welding but keen to learn and take on as much of the work as I can I intend to get myself on an evening course or two. So the first of potentially many questions, as the project progresses, is: which system is going to best for my needs Mig or Tig?

I would think we are looking at a minimum of 1/25 inch steel. Mainly patching here and there and when a bit more proficient a bit of structural work. Anything below the waterline will be left to those who weld for a living… for obvious reasons!

Cheers

Paul

 

[PTvor]

TIG is really a workshop technique, for use on the flat unless you have a lot of skill. It's also more involved with maintaining and choosing tungstens etc and the equipment is quite dear - to get anything any good. It uses a lot of pure argon. It's capable of superb results and you can weld a range of metals apart from steel, titanium, magnesium etc.

MIG is generally used for car bodies and steel less than 3mm thick down to about 0.7mm. You can get MIG welders which will weld thicker steel and do it all day, but they tend to be expensive. The duty cycles of hobby type MIG welders usually drop off rapidly as they are used on their higher power settings. MIG can be used with CO2. A rule of thumb for a MIG welder is 1 Amp per thou of metal thickness.

1/25" is almost exactly 1mm or 40 thou.

With MIG and TIG there's a problem welding outside with the gas shield being blown away, so you often have to arrange some wind shielding. There is gasless MIG wire, but it's expensive and inferior to using ordinary MIG wire and gas.

Arc comes into its own welding steel thicker than 3mm, although you can go down to 1.5mm with practice. It can tolerate a fair amount of rust and dirt (although you should always aim to clean back to bright metal) and it can tolerate a reasonable amount of wind.

From what you say, MIG is what you should be looking at. There are inverter MIGs which can also do arc. They have other advantages such as being much lighter and more efficient, so you can weld to more amps from an ordinary 13A socket. The disadvantage is that they are not as robust and are harder to fix if they go wrong.

 

[BrokenBiker]

I would opt for mig for what you need. could always go down the route of the IFL 3in1 inverter. mig tig and stick all in one unit

 

[penfold]

1/25"(1mm) plating on a boat? Are you sure it's not 1/4"(6mm)? ARC would be usual for boat work, although MIG and TIG can be used with consideration and deep pockets.

 

[BrokenBiker]

1/25"(1mm) plating on a boat? Are you sure it's not 1/4"(6mm)? ARC would be usual for boat work, although MIG and TIG can be used with consideration and deep pockets.

I think he is only going to deal with steelwork above the water line. I know nothing of boats really but I am assuming that any steelwork on the deck wouldn't need to be as thick as the steel that sits under the water

 

[bobw1]

Steel in narrow boats is normally 10mm for the bottom, 6mm for the sides and 4mm for the roof.

Wish I still had mine..
Bob

 

[BrokenBiker]

I stand corrected. I assumed that the roof may be closer to car body work thicknesses. with those thicknesses I would be looking at a decent dc inverter arc welder. 200 amps or higher

 

[PTvor]

The thickness of the steel usually being welded is very important in deciding what sort of welder.

If there's a lot of thicker steel to be welded there's a question of the electricity supply. Being stuck with a 13A socket and extension leads for instance, or having to use a generator, which brings another lot of problems.

 

[bobw1]

Cabin sides and roof are usually 4mm as I said although I'm sure 3mm is not unheard of along with 8mm bottoms. The roof needs to be fairly stiff because people walk on them all the time. It's often the quickest way from bow to stern (look at me all nautical) nice place to sit and get hammered to. As for what welder to buy there are plenty of people better able to advise you on here but thinking back to the kinds of jobs I did on mine an arc welder of some description would be most useful. A plasma cutter would have seen some use. A friend of mine and I once cut a doorway through a bulkhead with a load of 1/8 drillbits and a hammer and chisel. If someone ever invents the cordless paint brush that would be even more use!

Got me thinking about boats now
Bob

 

[Shox Dr]

An R-tech inverter ARC welder would be my choice, more than capable of welding anything on your boat, will run happily on a 60' extention. And might even run on a genny, though I would be asking the question if that is a requirement.




(can be used as a scratch start TIG as well with the bits and gas)

 

[Lawnmowerboy]

You need an avr generator to tun an inverter welder as they can easily go pop if not.

 

[Paul McCabe]

Hi Guy's, thanks for your quick responses. So the deliberate mistake... not 1/25" more like 1/4"! I'll try to engage brain properly from now on
The boat was build in 1943, looks like a mix of rivet and weld depending on where you look. Its 105ft LOA and 21ft in the beam and she displaces about 100 tonnes... pretty substantial. I'll post some pictures when I have sorted through what I took on Friday. If I can get her at a good price and find a mooring down here in Southampton I'll be making an offer on her. She's not in too bad a condition for her age, has a few bits missing and in order to gain a little more space (berths) I have to cut some internal steel away and reconfigure bits here and there. It will all be pretty much the same gauge steel, as I said anything under the waterline and therefore heavier gauge will be welded by someone with considerably more experience.
The R-Tech inverter ARC welder is cheap enough to make it a contender. I'll have a look to see if the local college run an ARC welding course.

 

[PTvor]

'So the deliberate mistake... not 1/25" more like 1/4"'

Arc. Arc all the way. After plenty of practice that is, and I doubt that one course at a local college will deal with positional arc welding which you'll need to be well into before attempting it.

As well as inverters there are oil filled welders which will put up with heavy use, are about second hand for around a ton, and are worth thinking about.

 

[Paul McCabe]

Thanks… I appreciate that one night school course isn't going to give me the skills to take on such jobs as will be required but it will, I hope, give me the confidence to tackle a few of the easier jobs to start with whilst I gain some experience. The beauty of this project is, if it gets of the ground, I can practice to my hearts content as I only have to please myself. Probably the biggest project, of any kind, that I'll have taken on

Paul

 

[bobw1]

105 foot long! That's not a houseboat it's a ship! No idea what thickness they would have used for that but it's going to be thicker than anything I suggested. Can't wait to see the pics.

Bob

 

[Robotstar5]

The beauty of this project is, if it gets of the ground, I can practice to my hearts content as I only have to please myself.

As it's 100 ton be careful working underneath

 

[penfold]

Given it's a large steel vessel I wouldn't be surprised if there's already a chunky arc welder hard-wired into the engine room, and a coil of cable long enough to reach all around.