I ran across a couple tube bending tools at Harbor Freight today that were on sale. They were so cheap I decided to pick them up along with some scrap copper tubing of different sizes to experiment on. I was able to get good quality bends of 180 degrees on the smaller diameter tubing. When the tubing got to 3/8" however, I was unable to get a decent bend beyond 90 degrees. I need to do some more test bends to determine how small the radius can be per the tubing size. Wish I had the more expensive U.S. brand bender to do some comparison tests. Unfortunately, the benders sold by the popular tool suppliers cost about 10 times what I paid for the Harbor Freight offering. I suspect these tools will suffice for the fabrication required on the RV-8.
