Related the rusty boat deck described in my previous question "Cutting bolt with minimal heat" I encountered a new problem.
Most of the steel of my 4 mm mild steel deck is fortunately still there, but there is one place where a section of about 20x40 cm is completely eaten away by rust. I=B4m planning to cut out this area as far until the surrounding steel is again 3-4 mm and weld a new piece of metal in there. Only complication is that the deck is slightly curved. Not much, but enough to make a flat piece of steel plate look ugly there.
What I would like to ask is what the normal procedure is to fit a new4 mm mild steel piece in the hole following the curve of the surrounding area. The curve is mainly in one direction and in the middle approx 1 cm away from the "straight line". Perhaps there is also some (much smaller) slight curvature in the other direction.
I thought about preforming the metal on a roller, but measurement is not easy for that. I=B4d rather take some in-situ approach. Only the material is too thick to deform with simple tools. Perhaps welding some sort of long lever on the plate and use that to curve it while tacking every spot that is on the right position? And cutting the lever away afterwards? Or is it possible to use a propane burner to heat the material and have it bend itself?
Related to this I=B4m also not sure if any problems might occur after the piece is tack welded in the perfect position. Can it deform while make the final welding all around? I=B4ve heard that in bad repair jobs like this, the curving "flips" inward.
I=B4d be very happy with any comments on this.