B320

DESIGN: UniCopter ~ Dimension, Area & Drag - Drag

  Minimum Coefficient of Drag:

A streamlined shape having a 3/1 fineness ratio (length/diameter) gives the best value of CD, namely 0.045, which is 3.5% of the drag coefficient of an equivalent flat plate. I assume that this is the NACA 0033 profile. Try and get the cross sections of the UniCopter's fuselage that are parallel to the airflow close to this profile.

 Notes:

Drag is calculated by using the 'strip approach'; calculated by estimating the drag coefficient of individual two-dimensional fuselage x-sections. See: [RWA]

Torque - Pitch Coupling is attempting to raise the nose while the engine is driving the rotors. This takes place during forward flight (good) and during hover (not so good?). This does not take place during autorotation (good or not?)

Wind tunnel tests have generally led to the conclusion that streamlining individual bits and pieces without unduly blocking possible air paths between them leads to the lowest air drag. [RWP1, p.298]

 Crazy Idea:

The blades pass over the top of the fuselage at a rate of 6P. They are very close to the top of the fuselage and this will result in much turbulence. Consider;
  1. Giving the root of the blade a 'D' profile with the flat side down and close to the fuselage ~or~
  2. Let the 'roof' of the fuselage flex (I.e. a wave moving forward). Weird.

 Not So Crazy Idea:

Flare the root of the blades into the rotor hub so that there is a 'relatively' clean airflow in this area. Will any reduction in the root vortex result in a reduction in the tip vortex?

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Last Revised: February 17, 2007