- Do all helicopter blades spin the same way or do they rotate in opposite directions?
There are many different configurations of helicopter blades and theybdon't all rotate in the same direction.
Also there are helicopters , particularly military ones that have a rotor at each end of a long body.
There are also many helicopters with rotors one on top of each other rotating in opposite directions (Contra-rotating)
- Could someone explain construction and working of helicopter blades?
Frank Piaseki used steel tubing, spruce wood, birch plywood and fabric to construct the rotor blades of his PV-2. Today, almost all military and civilian rotor blades are made from polymer composites. Blades are designed with specific geometry that adapts them to the varying conditions of flight. Cross-section shapes of most rotor blades are not the same throughout the span. Shapes are varied along the blade radius to take advantage of the particular airspeed range experienced at each point on the blade, and to help balance the load between the root and tip. The blade may be built with a twist, so an airfoil section near the root has a larger pitch angle than a section near the tip. Without polymer composites, the complex airfoils of today's rotorcraft would likely not be possible.
- Do the blades on a helicopter spin clock wise or counter clock-wise?
It depends on the make and model of the helicopter. In general, American made helicopters spin counter-clockwise when looked at from above (it's an arbitrary convention, but we usually talk about them as if viewed from above, not the ground). European and Russian helicopters typically spin clockwise when viewed from above. Helicopters with two main rotors have each one spin in opposite directions so there is no need for a tail rotor to provide antitorque.
There is no advantage for the main rotor to spin one way or the other. It's just the convention of the manufacturers.