VStabi Pioneer of Flybarless

Main blade weight: The heavier the blade, the more energy is needed to alter its position. A light blade has more agility from servo inputs and will be better for the control circuit since it responds quickly. Unfortunately the auto-rotation behavior is poor with light blades since they retain little kinetic energy compared to heavier blades.

Center of Gravity: If the CG is nearly at the tip of the blade, more energy is required to move it. Vice versa, a blade with a COG nearly at the root has more agility and will be better for the control circuit. Unfortunately the auto-rotation behavior is poor since CG so close to the root it doesn't retain much kinetic energy.

A compromise is needed for overall weight and CG location. Most modern blades will work ok, but there is no guarantee. You don't need special "rigid" main blades as used in the past. The CG can be easily figured out on any modern blade as shown in the picture below.

Lead or lag: This characteristic (along with the airfoil shape) determines how a blade will steer through the air and the holding forces required by the servos. VStabi works best with blades without lead/lag or minimal lead. The lead will be measured as shown in the picture below.

A leading blade means the largest area of the airfoil proceeds before the point of CG. This results in a blade that wants to steer itself harder and harder as its deflected, like holding a sheet of cardboard upwind (into the oncoming wind). This means you (the servos) must fight to hold the blade at a specific angle.

A trailing blade will do the opposite, it wants to re-center itself more and more as it's deflected, much like holding a sheet of cardboard downwind (with the wind behind you). This means you (the servos) must fight to hold the blade at a specific angle.

A balanced blade means the blade pivots directly around its CG, so changing direction leaves minimal load on the servos. If the airfoil leads very slightly, this is OK with the VStabi.

To find you blade's lead/lag, hang the blade with a weighted plumb line and measure the difference of the blade nose to the string. This will give you some idea how the blade will perform.

Profile: Symmetrical blades are very popular for everything from sport flight to 3D and will perform very well with VStabi. For scale helis, semi-symmetrical blades are popular and will work fine as well.

Stiffness: The stiffness along both axis (bending and twisting) has a large influence on the control circuit. Use very stiff blades (e.g. made of high quality Carbon Fiber) to ensure they respond accurately to pitch changes. Flexible blades will respond in a "sloppy" manner and the feedback to the sensors will be mushy at best.