[EricH]

Originally Posted by Kusha

@EricH What's a vertical stir welder?

Start with a friction stir welder (a sampling can be seen in http://www.youtube.com/watch?v=jCe8-QYKZf4). Now, take one that will travel in a straight line only, and point that straight line at the ceiling. You get a vertical friction stir welder. We use ours to build rockets.