This video on TIG welding Aluminum Lap joints shows up close arc shots along with a technique that might help you avoid dipping your tungsten
My settings and details for these aluminum lap joints are:
120-135 amps
AC balance 67%
AC frequency 100hz
Argon set to 20cfh for the furick #8 pro cup and 15 for ally #5 cup
3/32" (2.4mm) 2% lanthanated electrode
3/32" (2.4mm) 4043 filler metal (1/16" (1.6mm) filler metal for tack welds)
