patching floorpan

[MAK]

Finally got my nerve up to start cutting and patching on my floorpan yesterday. Not great work but hopefully my technique will have improved by the time I move from the floor to the body panels. The main panel is just laying there until I cut another small section out up to ward the front right corner, but most of what you see in the picture is just surface rust.
http://onlinecache.com/F100/
I do have a few questions for the old pros here. I was having a lot of trouble getting good penetration. I adjusted voltage, wire speed, stickout, etc but still had trouble. Is it because I didn't leave enough gap between the pieces butted together or because I've not learned to hold it in one place long enough to get a little hotter without burning through?
Before I can start on the main floor welding I need to finish cutting over to the kick panel on the upper left corner. However, I can't get my cut-off wheel all the way to the kick panel without cutting it and other parts I don't want to. Any suggestions? How do you get in to those tight corners?
Thanks

[fordman]

a sawzall maybe.

[MAK]

I used an air chisel to separate the pan from the cab mount and side support shelf. Problem is that upper left corner that is over the support shelf and next to the kick panel. Just can't get in with a sawz-all or the cut-off wheel. Maybe I'm just trying to keep the cut too straight... I may try the dremel with some cut-off discs.
Welder is a Hobart 140 with an Argon/CO2 mix and Harris "20 Gauge" .030 wire. Best results have been with the voltage setting at 2 and the wire speed about 30 or a little more.
Back side of my weld looked similar to your examples. I even crawled underneath and hit a few of the spots with poor penetration...

[fordman]

yea a dremel might be the way to go.

[MadMaxetc]

I used an air chisel to separate the pan from the cab mount and side support shelf. Problem is that upper left corner that is over the support shelf and next to the kick panel. Just can't get in with a sawz-all or the cut-off wheel. Maybe I'm just trying to keep the cut too straight... I may try the dremel with some cut-off discs.
Welder is a Hobart 140 with an Argon/CO2 mix and Harris "20 Gauge" .030 wire. Best results have been with the voltage setting at 2 and the wire speed about 30 or a little more.
Back side of my weld looked similar to your examples. I even crawled underneath and hit a few of the spots with poor penetration...

I have the same setup. I would go buy some .024" wire and tips. I makes a big differance. I usualu set my wire speed down 5 from what they say on the chart.