STRAIGHT SEAM WELDS

I got all of the straight seams welded today (still on schedule). There are a few strips where the welds could be better so I'm thinking about whether it's worth grinding them down and redoing.

From reading that the surface of the metal has a large effect on weld quality, I looked at different ways of cleaning the metal in preparation for welding:
Sand-paper

Brush

Disk Grinder

I chose to use disk grinder as it cleaned the metal quickly and well:

I also found that parts where the metal joint had a gap didn't weld as well as when they were butted up tight.