Increasing the diameter inevitably entails side effects that can also affect takeoff distance, such as the inertia of longer blades, and the lower initial rpm if the same pre-launcher power.

In my comparison I assumed the same coning for the same vibration 2/rev. which requires heavier blades, therefore the take-off weight is increased by the same amount to retain the same payload.

With

**D = 6.45 m** c = 0.18 m Blade mass = 7.5 kg, Flight rpm: 395 at 90 km/h Total mass = 216 kg Pre-launcher power: 2 kW giving 260 rpm

Calculated rolling

**distance: 82 m **
With

** D = 7.45 m** c = 0.18 m Blade mass = 10 kg Flight rpm 323 at 90 km/h Total mass = 221 kg Pre-launcher power: 2 kW giving 215 rpm due to increased diameter

Calculated rolling

**distance: 79 m**
Insignificant difference !

**View attachment 1160550**
Insignificant difference

Data used:

Chord : 0.18 m

Aerodynamic pitch setting: 3.5 degrees

Static propeller thrust: 1200 N

Frame drag area (S.Cd): 0.4 m2

Rolling coefficient on grass: 4%.

Rotor shaft: +20 degrees /ground