B471

DESIGN: ~ Single-Bladed All Electric Rotor - Blade & Arms

Overview:

Note

Blade:

Rotor profile Drag: A NACA 0025 to NACA0033 is very aerodynamic therefore the braces each side of the round motor should have this NACA profile to reduce drag. In addition, the engine requires cooling air, therefor if the motor side has a higher drag than the blade side a 'scoop' could be placed at the root of the blade's leading edge and the air flow down the a hollow brace.

Carbon composite construction.

-10º twist approximately

See pictures of fiberglass single rotor blade for the Bo-102 further down this page. [Source TH3 p.119] The high rigidity of this blade should go a long way in overcoming Chuck Beaty's concern about the blade and the counterweight not acting in unison.

Active Blade Twist:

Idea: [pitch angles are approximate] The initial intention was to have the motor-blade spar as torsionally rigid as possible. This thinking was to assured that the pitch rotation over the total span of the blade was as close as possible to the rotation of the motor. The concern was that a CW rotation by the motor, which is opposed by the torque-pitch mechanism at the hub, would result in a CCW rotation at the blade tip.

It now appears that a small amount of rotational flexibility [active blade twist] may be advantageous.

Consider the case of the rotor at rest. In this situation we will assume that the blade has no built-in twist and the pitches at the motor, the root of the blade and the tip of the blade are all 0º .

Now consider the case of powered flight. There is a strong 'driving' torque from the motor. The CW rotation of the motor will cause it to have a 'pitch of 20º. The torque-pitch mechanism will present a resistance to this rotation. Therefor it and the nearby root of the blade will have a pitch of 15º. However, the tip will only have a pitch of 5º because the rotational flexibility will remove a portion of the rotation.

Now consider the case autorotation. There is no 'driving' torque from the motor. In fact, the powertrain and motor will be consuming a small amount of 'driven torque. This situation will result in a reversal, albeit small, of the above paragraph. The root of the blade will have a -1º pitch and the tip will have a +1º pitch, just like the blades of a gyrocopter.

In theory, this results in the attractive situation of a reasonable negative twist during powered flight and a small positive twist during autorotation. However, loss of motor power means loss of flight control; beyond what might be obtainable from the vertical and horizontal stabilizers. Note that the descent rate will be low because of the low disk loading.

Consider this as the basis for the blade; but a much stronger spar:

SynchroLite ~ Rotor - Blade - VR-7b - Composite

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Initially displayed: January 30, 2006 ~ Last Revised: June 19, 2007

The above utility invention RE ACTIVE BLADE TWIST is openly and publicly disclosed on the Internet to negate an entity from patenting it, to the exclusion of all others whom may wish to use it. ~ Reference patent law 35 U.S.C. 102 A person shall be entitled to a patent unless - (a) the invention was known ... by others in this country, ..., before the invention thereof by the applicant for patent.