Item 1162
DESIGN: Dragonfly ~
Rotor - Disk - Undersling
Undersling at Hover out of Ground Effect, Based on VR-7 Blade:
CA BEATY's Undersling Excel program on Rotorcraft web site
34800 x ([Gross Wt] - [Rotor Wt]) / ([Rotor wt] x [Rotor RPM]^2)
Calculation for Dragonfly.
34800 x ( (550 / 2) - 21 ) / ( 21 x 700^2 ) = .710". This algorithm is probably only good for a 2-blade rotor.
Based on Horizontal Alignment of the Two Blades CG's and the Teetering Hinge.
From Dragonfly ~ Rotor - Disk - Coning Angle the coning angle is 1.528 degrees.
From DESIGN: SynchroLite ~ Rotor - Disk - Centers, Radii & Moments the radius of the center of gravity is at 37.812". An approximation for the Dragonfly will be 37.812" * Scale of 0.87358 = 33.03"
The vertical dimension is sin(1.528 degrees) * 33.03" = 0.8808"
Undersling and Mean Load (normal steady state load):
When the craft is hovering out of ground effect, the tip path plane will be aligned with the mast plane. The amount of undersling is of little importance in this situation. The amount of undersling will be of importance when the two planes are not aligned, such as during fast forward flight and changes of orientating of the craft. At these times, the rotor will usually be under loads that are greater than that required to hover out of ground effect. Therefore, it may be advantageous to increase the amount of undersling to an amount more than the value(s) calculated above.
Additional Information:
DESIGN: SynchroLite ~ Rotor - Disk - Undersling
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Last Revised: March 15, 2003