Selection and Evaluation of an RC Model Design
Tips on choosing the best scale plane for an RC model design
Typical RC trainer with ideal moments and surface areas
Once an RC model design is proposed for a typical sport flyer, we have complete freedom to make the model airplane dimensions as needed to ensure a well flying aircraft with minimum design problems. Typically the nose moment should be long enough to ensure an easily located center of gravity. A generous tail moment provides the aircraft design with smooth flight characteristics. We can adjust the size of the wing and tail surface area as needed for stable flight and no adverse yaw characteristics. Even such mundane considerations as fuselage width can be tailored to permit proper servo and receiver installation in your RC model design.
Fokker Triplane has a very short nose moment
If you wish to draw up a scale RC model design, you still need to take into account the above considerations as you select a good candidate. Some full scale antique aircraft, such as the Antoinette, have narrow fuselages that make RC equipment placement difficult. Other early flyers, such as the Sopwith Camel or Fokker Triplane, have a very short nose moment that makes balancing the finished RC model design at the proper center of gravity very challenging. Your scale model’s landing gear should also be considered as part of your design selection process. The landing gear should be visually appealing, not too hard to fabricate, and provide a light, stable and strong structure for your model.
Design inspirations from Demoiselle
These model aircraft design considerations all came into play as I built the Sig Demoiselle from a kit, followed by preparation of the TurboCAD drawings for my 1912 Blackburn monoplane construction plans. While I had no part of the Demoiselle design process, I remain fascinated with how the Sig model designer overcame some very interesting challenges on this unique model aircraft. The Demoiselle has a simple open framework fuselage, an all moving tail plane and an extremely short nose moment. I gained a lot of insight as to the proper wing area, incidence and attachment methods for a well flying scale indoor RC model design. I adapted many of the Demoiselle’s design attributes into the Blackburn.
Blackburn monoplane has ideal moments and areas for a docile RC model airplane
I settled on the Blackburn for my scale RC project for a variety of reasons. First, I liked the overall look of the Blackburn. The plane’s layout was sound, and lent itself well for a scale indoor RC model airplane. There was no doubt that the Blackburn’s nose moment was sufficient, with a flared cowl large enough to enclose a typical electric motor. A key design requirement was adequate fuselage width for the radio gear. I met this with the use of micro servos poking out the rear of the fuselage. The landing gear had a strong fore and aft strut arrangement that would be easy to fabricate. The tail moment and surface areas are very generous. This would be an important consideration, as my Blackburn would have just three channels of control, and needed the full authority of the rudder and elevator for successful flight.
Keep your design light
A key consideration for any RC model design and associated RC plane plan is to keep the finished airplane light. This is true with any model, but especially so with an electric powered indoor flyer. I am always surprised at how strong a lightweight balsa structure can be, without the need for heavy plywood reinforcement. The use of vibration free electric motors offers further inducement to “build in lightness” to your indoor electric design. Remember that a light RC airplane will always fly better than the same model design at a heavier weight.
Sig Demoiselle scale RC model airplane kit
You will need a minimum of three control channels for your RC model design: rudder, elevator and throttle. Some of the smaller ready to fly micro indoor models get by on two channels. But stick with a minimum of three channels for your project. Newer micro RC radios are coming out with four channels as well. If your budget allows, go ahead and plan on a four channel installation adding the aileron function. And with the use of a single transmitter, such as the Spektrum DX6i, binded to multiple models, the cost of RC flight electronics is much more affordable than the old days of one transmitter per RC plane.
A final note for the new RC model designer, and that is to keep your flying skills sharp. Scale RC models look great, but oftentimes can be more challenging to fly than a sport RC model. Ensure you get in enough stick time, either with a RTF model or on a computer flight simulator, before taking your own new scale project for a first maiden flight.