Weld fill interior side Hull putting whilst boat is in the water?

[Paliman]

Hey, any advice would be greatly appreciated. My steel Hull boat had water sitting in the cabin for a while and has done a number rusting it from the inside. My question is, can I fill the pitting with weld whilst the boat is in the water or will the heat melt the water side blacking which would leave it vulnerable this winter. 

Thanks a lot 

[matty40s]

You will struggle to get the metal hot enough to weld effectively with the large water heat sink on the other side, and yes, it would affect the blacking. 

[Tracy D'arth]

Just now, matty40s said:

You will struggle to get the metal hot enough to weld effectively with the large water heat sink on the other side, and yes, it would affect the blacking. 

  You will be a brave man to weld inside of a rust hole whilst in the water!

 

Your weld will be rubbish unless you are running a massive current in which case you will remove the blacking and risk penetrating the hull as well. We weld on fuel tanks and it takes a lot of current to get a good weld, its a dodgy business but someone has to do it.

[Neil2]

Years ago we had our skin tank re- welded (in the water) when it sprang a leak - surely that's even more hazardous given the plating is usually thinner than the base.  It was stick welded IIRC and a swine to get at but the guy did a great job.

 

[David Mack]

I would leave sorting out the inside pitting until you have the boat out of the water. Then you can do all the welding required (inside and out) before reblacking the exterior.

If you are worried about internal corrosion in the meantime I would wire brush to remove loose rust then paint on vactan or similar rust converter.

[roland elsdon]

Personal experience of hullside welding on the footings, whilst in the water results in the arc going out. I had to shove the rod through the hole, before starting other temp repairs

[Paliman]

Thanks all for the replies. I'll leave it till its next out the water. Take care, folks. 

[DHutch]

Yeah, I have welded odd bits to the inside of the hull while in the water, with a 160A mig set which isnt really up to the job to start with, and the stuff as stuck to the hull ok and looks reasonable with a thick coal of epoxy ali over the top.

 

However, the length of weld was good and long and the whole thing designed with the expectation that the penetration would be fairly poor, welded to a 10mm base plate or 6mm side plate, that was in good condition and clean etc. 

 

If you are welding up rusted pits, in thin plate, I too would be worried that you might blow holes through and end up much worse off than you started! Equally, unless the pitting is really quite a small area, or a small number of really quite discrete pits in and otherwise reasonable plate, it doesnt take long until its going to be quicker to cut out the plate and replace it.

 

 

Daniel

[waterworks]

21 hours ago, matty40s said:

You will struggle to get the metal hot enough to weld effectively with the large water heat sink on the other side, and yes, it would affect the blacking. 

You just made that up.

 

( I'm a welder )

20 hours ago, roland elsdon said:

Personal experience of hullside welding on the footings, whilst in the water results in the arc going out. I had to shove the rod through the hole, before starting other temp repairs

No reason that should happen but operator error. 

[waterworks]

A bulkhead put in ( by me ) while in the water. 

[matty40s]

Amazing how modern technology helps reduce pictures to 1990s standards of clarity 

Edited September 7, 2021 by matty40s