Jack was a master sheet metal worker, and was roped into using his skills on an obscure project to turn the sketches for the droid into something that could be constructed out of aluminium sheets.
I always knew he'd helped make part of R2-D2. However I only found this photo in recent years and have since learned that he was actually instrumental to the construction of the entire droid, particularly with working out how to machine the complex shapes like the dome and legs out of single sheets of aluminium.
He didn't just build one either, he ended up constructing a handful of the droids for various uses in the film. I still have no idea how he did it, especially without modern software and computer-controlled machining.
Unfortunately I never got to know him as he died when I was a baby, though I have a feeling we share a lot in common.
I also have his old Dragon 32 computer that he was using to learn programming in the 1980s, with reams of hand-written code that still works on the computer.