47-59 home made portable planishing hammer build

[leegreen]

I was lucky enough to inherit my father's Watervliet, I don't know where he acquired it, but he was into airplanes and involved in the local experimental aircraft association, so probably a connection there. Edmonton has EAA, you might ask around.
If you google you will find pictures of the shapes of hoops they made for these, similar to trick tools. the pipe is 1 5/16" OD with a wall thickness of 1/8" . You'd loose some effectiveness making a long oval hoop, but moving the metal slower is probably an advantage for what you need to do. Your neighbors will love the noise.

They have large diameter pistons and can run on a low pressure, like 20 PSI, lower pressure lets you take your time.
I have not used it on a large flat panel like a roof, but is sure smooths out a fender quick. You could easily overdue it and make a bubble.

I would not say my hammer is light, and neither of the hoops I have is roof length. I think you'd need a helper or something rigged up to hang it from, bungees or something

Post pictures, maybe we can help. A backer would make it a lot harder to move the metal around after welding.