I have yet to see a significant female car designer / builder. Maybe there's a few in the automotive industry as designers and not just the hot rod industry, I hope anyways. :)
There are quite a few women welders around my area. My college hosts a free "Women in Welding" workshop that introduces ladies to mig, plasma cutting, and stick. They also have guest speakers who are successful ladies welding for careers. It was great! And the workshop fills up every time.
It'll be interesting to see how few females there will be in the industry I'm going into. There's only 3 women (including me) in my college program currently out of... Maybe 50+ men? Going to school for Mechatronics / industrial automation BTW.
