Metal and wood and a little hard work.
The cheapest way to build a helicopter is to build a LOT of them. This way you get economies of scale.
That depends on what level your talking about in the level of Cat woman you will have to build it and in other levels you either have to build it or build a thing you have to push and get the helicopter out of a shed or something.
He didn't have or build an actual helicopter. It was just a sketch.
Igor never flew a helicopter, but he did build one though.
yes it i they build it in the 1945 it was one of the first navy helicopters to be in army
Can you build the transmission and rotor hub, that's the real point
Many very complex tools.
You need a design for a helicopter. That design will tell you what materials you need...because every heli has different materials in it. The things you need to build a Robinson R-22 are different from the things you need to build a Sikorsky CH-53E.
Almost the same as the other similar aircraft engines. And depends on the size of the helicopter, consequently to the power of the engine.
Helicopters have been built every year since about 1940
He drew some helicopter like machine graphics. He had the insight, just not the available technology to build one.
He did build a working model of one.