NDI Question:Device to measure wall thickness of closed tube

[Edward Sheetmetalhands]

I am looking at doing a set of detailed measurements to generate engineering drawings of a vintage airframe. The drawings otherwise do not exist (even with the Smithsonian). Is there a way to measure the wall thickness of closed steel tubing 1.5" diameter and less without doing anything destructive? I remember Boeing used an NDI device that could measure thickness of sheetmetal (especially when inspecting chemically milled pockets) by placing the probe on the part... but am not sure what it was called, or whether or not something like that would work on a curved surface like tubing.

[b29flteng]

Digital Thickness ultra sound

[The Inspector]

Ask around your local drag racers and sports car racers as both SCCA and NHRA use ultrasound to measure tubing thicknesses and any track official @ any sanctioned NHRA strip can get you the name of the local outfit that does tech for local drag cars and/or sports car tech. You could also ask the guys @ the local chassis fabrication shops that build racing roll bars and chassis. The cost should be almost pocket change unless you've got a storage yard of tubes needing measuring.
OR, you could resort to the old timey method and drill a 3/16th dia. hole in the tube, deburr the inside of hole and measure with calipers then weld and file.