RE: Sceady EVO .50 parts
I'll answer the blade difference question real quick.
Quoted from here:
[link]http://avia.russian.ee/theory/index.html[/link]
(Referring to rotor blades)
"One type has exactly the same amount of curvature on the bottom as on the top: this is often referred to as a "symmetrical" airfoil. Many helicopter rotor blades have this shape — a stretched-out teardrop curve from the leading edge to the trailing edge that is exactly the same on both the top and the bottom. In comparison with the more conventionally shaped airfoils the symmetrical airfoil offers several advantages, particularly for the rotor blades of a helicopter. One of the most important of these is a highly desirable aerodynamic characteristic: very little center-of-pressure change under different angles of attack (the center of pressure is generally considered to be the center of the lift force acting on the wing). (With conventional airfoils that have a full curve only on top, as the angle of attack is increased the center of pressure moves forward considerably, and this complicates the problem of stabilizing and controlling the lifting surface.) Other desirable features of a rotor blade designed with a symmetrical airfoil are structural rather than aerodynamic. For one thing they are generally easier to manufacture, since the top and bottom skins are identical and other parts may be as well."