Bensen B9 inspired coaxial helicopter


Jan 28, 2021
Home built helicopter
Total Flight Time
I am looking for some thoughts about the potential of a fixed pitch coaxial helicopter I have been building. I have carried out tests with only a propeller loading one of the rotors and the drive system worked well and achieved full engine/rotor rpm. I have nearly finished the rotor blades and aw95 style rotor hub carriers, so will testing the system with blades within the next 6 weeks.
I have no experience in testing or building a helicopter previously but will tether the machine during any tests. Any advice or thoughts would be very welcome.
I'm pinning my hopes that the Bensen B9 did fly and the design has the potential to get airborne but I'm not sure as I haven't seen any other craft of this exact type fly.
Here are some of the specifications :-
Engine Johnson Outboard 60hp 2 stroke 55lbs/ft torque
Rotor gear reduction 5.6:1
Rotor Diameter 4.3m/14.1ft
Rotor RPM 900
rotor tip speed 453mph
Airfoil section 0012
Blade chord 4.75"
Blade Centripetal force 2757kg/6078 lbs
Blade COM from axis 1169.5mm/46"
Blade Weight 2.6kg/5.73lbs
Solidity Ratio 0.07:1
Disc Loading 1.625lbs/ft2
Empty weight 130kg/286lbs
AUW 240kg/529lbs
Teeter undersling 25.5mm
cone angle 1.25 degrees

I've done a couple videos on youtube to explain more about it. Thanks for your time Regards Ben