If you are talking about bending tubing that is a way to bend tubing tighter than in could collapse due to tensile strain. Packing the tubing with sand keeps it round while bending it. There are other techniques as well. Old hot rodders used sand to bend headers.i found a photo of wing rib bending over a 16 inch tire, with the tube filled with sand or rice.who has tried this and can anyone explain it more?
I have seen ribs bent around the leading edge where they allowed the tube to go flat for that portion then back to full round for the majority of the chord length. Works fine. Also seen tubing flattened and riveted to a sheet metal flanged leading edge piece. All kinds of ways to skin that cat.No need to fill with sand.
It will bend without kinking. (wont bend around leading edge)
The hard part is all that spring back makes getting the curve to match your airfoil can be difficult.