[Veselin Kolev]

1. you need aluminum feed wire
2. you need pure argon gas (not CO2)
3. If you're welding a chassis, and you weld the top side first and then the bottom, the entire chassis will curve upwards. Hence, first tack weld the entire thing together and then weld top-bottom-top-bottom, etc, flipping the frame over every weld. And make sure you do the symetrical side so you dont get corner warping.

If it's your first time welding aluminum, practice a lot on scrap metal first. Make sure everything is grounded cleanly and securely. Sand the oxidation off the ground contact and the places that will be welded.

Other than that, MIG and TIG welding can be almost equally as effective. In my experience TIG makes a better looking weld, but in FIRST I doubt you care.