Sunday, March 20, 2011

Welding stuff for your boat

Chainplates with SS inserts and edging
The of the best boat refitting skills I have is welding, It took me an adult education course and two years at night school classes to get really confident, (I have dreams of building my own metal boat one day..) So far all the pieces I have welded onto Snow Petrel have stayed put... (touch wood - metal?). And some of them are important like the tabernacle, and chainplates. My metalwork is not like the classy shiny stuff that you see coming from a fancy workshop with their TIG welders and polishers, it is more industrial, without the mirror polish and delicate weld beads but still does it's job just fine.

In fact I ended up replacing all Snow Petrel's deck fittings with (much better) welded on homemade stainless steel fittings. Now the only holes in the boat are the windows, hatches and winch bolts. I now have no deck leaks! (an incredible luxury), less rust traps and better designed gear.

My complete kit fits into a small suitcase, (except for the helmet), and can easily live onboard. At the moment I am welding up a little wood heater to replace my smelly diesel heater. I get alot of satisfaction from welding and I really think that If you plan to go to high latitudes a metal boat is a pretty good idea, and if you have a steel boat learning some basic welding skills makes sense. Welding aluminium as a different ball game, much harder, and expensive bigger welders are needed.
My incomplete fireplace door, Special fire glass is needed
It always surprises me that most budget sailors are happy to do their own woodwork, canvas work and rigging but bulk at even the most basic metalwork... If an uncoordinated numpty like me can do it, then most of the budget sailor population should be capable of learning and with some pretty basic skills, and a small amount of equipment some useful gear can be knocked up quickly and permanently from stainless steel. Even If you aren't happy welding you can always save alot of money by cutting out the parts and getting them welded up professionally (or by that mate for a 6 pack or two of beers....). If you take a few pieces of metal into any shop and ask them hust to weld them together it is normally pretty cheap, and they can often do it while you wait. Much of the cost is in designing, cutting and polishing the job.

Some basic tools needed -

A small DC inverter stick welder,  much better than the my old AC welder because it is way smaller lighter and has a much better duty cycle (It can run at 100 amps for 25% of the time, enough for most welding on a yacht), and it will happily run off any crappy power source, even what you might get at the end of an old wharf, or up a mast (I have chucked it over my shoulder and welded at the masthead). Get one that can run off a generator. Or alternately an onboard alternator welder can be used if desperate.

A welding helmet with an auto darkening lens is much easier to use.. also good quality respirator that fits under the helmet is essential to keep the worst of the nasty welding fumes away from your delicate lungs.

Welding Rods: I use 316L for welding SS to SS, 309L for welding SS to mild steel, and 6013 or 6012 rods for mild steel. Keep them very dry, humidity can effect the flux coating. 

A 5 inch angle grinder, I went though a few cheapies until I bought an expensive one. Make sure its a 5 inch with the big stud, taking discs with a 22.2 mm centre hole, not the toy 4 inch ones. I normally don't bother with a 9 inch grinder (even though I have one..) the 5 inch can do almost everything much better and is safer.

A heap of skinny 1mm cutting disks for the 5 inch grinder. (sorry about the mixed units, blame the french or the yanks... ) These things are magic, They cut through SS like its butter and leave a nice clean cut. I also assume they cut though fingers and other body parts just as well so be very careful to secure the work well (Like in a vice), always use the guards, and wear leather gloves and really good quality eye and ear protection... If you can't work out what the fuss about safety gear is, please never go to sea and preferably don't go very far from a well equipped hospital...
The most Important gear.. + Add Earmuffs and suitable clothes.
You will also want a flap disk or two for smoothing off edges, and those ugly lumps of weld, Its really just sandpaper for stainless steel, but it's the easiest way to clean it all up. SS grinding disks are also available, and remove metal faster, but flap disks still needed to finish the job. you can use a polishing wheel if you want, but I normaly use fine flap disks.

Add chipping hammers, wire brushes (SS wire brush For SS only), centre punch, cutting fluid for drilling holes and you are set. Drilling SS is a prick, sharp drill bits, lots of cutting fluid and a slow drill speed with lots of pressure are needed. Ideally a drill press for big holes... It is usually cheaper to take it in to a workshop and get them to drill any large holes rather than trash all your drill bits. A workshop can also cut out stainless steel quickly and easily into complex shapes with a plasma cutter - this can be very useful.

You can use pickling paste to clean up the welds an make them look shiny but it is seriously nasty stuff so I normally don't bother. They can just go very slightly rusty, no big drama if the peice is properly oversized (see here for more info on surface cleaning)

I used to get most of my material from scrap metal yards, but these days it is harder to find it this way, so I am forced to buy it. 304 is fine but get 316 if you can afford it. I have some dodgy stainless on my bow roller. It has a rusted to nice patina that I quite like, and the rust doesn't seem to be to getting any worse. Old rod rigging is awesome as SS edging for any non load bearing application. I collect old stainless steel fittings for parts that can be cut up or modified to make new fittings. 

I am always careful not to rely on stainless unless it is massively overbuilt, It is tricky stuff and can fatigue or fail without much warning. Also when welding and grinding beware of heat build up and sparks. Be very careful about fire risks, I have seen a quite a few burnt out steel hulls, and nearly had a nasty fire inside Snow Petrel, Some ports require a hotwork permit. And it is not allowed on most of the better class marinas or slipways... find somewhere abit more industrial. Oh and also grind well away from anything shiny, white or expensive. grinding dust blows along way and then rusts....


  1. Great post, Ben. Your enthusiasm and practicality is infectious!

    Couple of additional points about stainless which some people may not realise.
    It is prone to harden up wickedly if it's deformed. This is widely known, but there are some nuances which possibly are not.

    Firstly, it's best not to centrepunch holes you plan to drill if you can avoid it. One way is to clamp a piece of scrap, with a predrilled hole (can be plain steel) over the place where you want to drill.

    Another (if the position is not too fussy) is to put a patch of masking tape at the position you need to drill - mark a cross on it. The tape helps stop the drill skidding about. Particularly useful if you're drilling onto a convex surface, like tubing. (But here you'll need a centrepop as well, at the very least)

    So if you DO need to centrepunch SS, grind the end of the punch to a four sided pyramid, rather than a conical point. Similar angle, ie 90 degrees "included". This will require less force to make an indent, with less "work hardening" as a result.

    The problem with work hardening is that the first thing it does is take the sharp edge off the drill. The drill then rubs (ie deforms) the material it's trying to force a hole through, which in turn bluntens the edge further... well, I'm sure you get the idea.

    Trickier than drilling stainless, to my way of thinking, is countersinking it. There's only one remedy: you won't get far with a countersinking bit from a hardware store, even the best they have.
    Go to a place which sells cutting tools to engineering workshops (preferably to toolmakers and their ilk) and get the best countersinking bit they have for hard metal in the size you need. Either three flutes or one is best for stainless, generally.

    And Ben's good advice to use a drill press counts double for countersinking. As a fringe benefit, you can set the depth stop to get a consistent diameter. Difficult enough drilling hand-held in steel; doubly so in stainless, where you have to push so hard (I forgot to mention, the other imperative with drilling also: don't ever trifle with the feed pressure: from the moment the drill contacts the work, apply the most force the drill can handle. Otherwise it rubs and off comes the sharp edge)

    1. Thanks Andrew, I really like the idea of using scrap steel as a guide, I will have to make up a few drilling jigs. Some excellent advice from you that is much appreciated. And one day I must get a drill press!


  2. Did you weld that little fireplace door? You have amazing welding skills. You are completely armored with safety gears and equipment which are things to be considered when doing this tough job. I hope you'll be able to build that dream metal boat of yours, and don't forget to update us when you do. =)

    Jeanette West

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