RCS Design Course – Theory and Practical Application

Individual theoretical treatises, selected at random from the vast body of material, are of little use to the average model builder, since the equally important or directly related peripheral topics are missing or inaccessible. The entire subject matter was covered in a design course conducted by Region 5 in November 1971, and it was from this group that the desire arose to publish this theoretical and practical treatise.

Heinrich Disler

1. Wing Geometry (Area, Aspect Ratio)
No. 6, December 1972
2. The Reynolds Number
No. 7, February 1973
3. The Polar Chart
No. 8, April 1973
4. The Airfoil
No. 9, June 1973
5. Model Design
No. 10, August 1973
6. Calculation Example
No. 11, October 1973
7. Calculation Example (Continued)
No. 12, December 1973

Calculation of Wingspan and Aspect Ratio for Non-Constant Geometric Wing Profiles.

In the following paper, I intend to present, in an easily understandable manner, a method for calculating the wingspan and aspect ratio of wings or tail surfaces, assuming a given area and internal profile depth.

As initial parameters for all calculations, we will use an RCS wing with an area of $50 \text{ dm}^2$ and an internal profile depth of $2.2 \text{ dm}$.

• F = Wing area in dm²
• b = Wingspan in dm
• t_i = inner airfoil depth in dm
• t_a = outer airfoil depth in dm
• t_m = average airfoil depth
• λ = wing aspect ratio

For aerodynamic reasons, t_a should not be less than 0.6 t_i.

This wing planform is probably the most commonly used in model aircraft.
In this case, we can no longer determine the wingspan b directly from t_m.
First, we need to consider what the ratio between the inner (rectangular) wing and the outer (trapezoidal) wing should be.
Wind tunnel tests have shown that, relative to half the wingspan, the optimal ratios are:
b_i = 2/3 b' and b_a = 1/3 b'