This is a newbe question . but what the heck is a flapping head and what is the difference between a flapping head and regular head ?

The flapping head has the each blade grips spindle rod bolted onto a a flat piece of steel that bolts to the head. Each blade grip has it's own and can flex up or down individually. Unlike a regular head that the spindle is one piece through the head for both blade holders. Having a one piece spindle for both blade grip has much less flex for 3D but the flapping head is more stable for scale, it let's the blade flex up like a real helo has, kind of like dihedral on an airplane.

The Concepts and early version of the Nexus had flapping heads. Most of the modern helis like the Raptor, Shuttle and EVO's have a 1 piece spindle going between the blade grips.

ok thanks guys I believe I got it . I will have a look at my heli heads. which both happen to be the two that barracuda menchened.