Finishing Undersides & Fuel Tank (Day 53 & 54)

It's not easy welding in an enclosed area with jackets, pants and boots on and in a 35 deg heat day but summer seems to have arrived early this year. I spent the whole weekend fixing imperfections in the welds, even though they were leak-free I still fixed any small holes I saw, just to be sure.
The bottoms were finished with a very light pass of 40 grit flap sand disc, took about 3 hours to do the underside of the hull with a 100mm grinder. I had a fail with the weld on bung, this is the 2nd time I have welded these on thinking that by leaving the bung in without the o-ring during welding is the right thing to do, just so the bung body doesn't deform. I was wrong; the bung thread will just melt and fuse into the body. Not the end of the world, the bung body will serve as a perfect 'doubler' for setting some screws into with some Duralac anti-corrosive paste. That way, any possible corrosion won’t be in the transom itself but in the 'doubler'. I decided to just weld-in a 38mm tube so it is the right size for a large plastic bung. I also continued some work on the fuel tank by TIG welding the tubing; I also trimmed the fuel sender down to specification for this particular tank size.
Next the lid will be TIG welded onto the tank body, pipes capped off and then he whole tank will be tested for leaks. With the keel, I decided to put in a 1/4" threaded, aluminium grub screw which will serve as a inspection port, it will just go in with some plumbers tape and I will spread some silicon over the top of it, maybe remove the grub screw and inspect the keel once every 12 months or so. Some may say it's overkill but it didn't really take much effort to do this at all.

I had to carefully grind the bung cap off after it fused into the bung body, just nicked one corner. You can see the 38mm tube to be welded in which is perfect for a large plastic bung.

38mm tube now fully TIG welded in and forms a new hole for the plastic bung.

Bottoms finished with a very light sanding with a 100mm flap disc, it actually looks great & i am pretty sure as oxide develops the luster will go and the sand marks less obvious.

Trimmed off water pick-up on the underside of the hull, pick-up aperture is slightly angled so water gets forced into it on the go, no need to run pumps whilst moving along.

View of the bow, underside finished

Large plastic bung will fit in nicely.

1/4" tapped hole for aluminium inspection port grub screw

Just some silicone over the top to finish it.

Fuel tank washed down and impurities after welding removed with a tooth brush and some soap then hosed out and left to dry.

Inside is clean now

TIG welded tubes to tank


  1. Nice pictures, which is about finishing undersides and fuel tank that will be more helpful for us. Keep sharing more & more.
    Tank Welding


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