Almost or many RC airplane enthusiast dream of having their favorite full size replica to bore holes in the sky. But it will not be easy just to copy the exact dimension of the full size airplane and then scale it down to what ever you desire, like for example 1/8 scale, ¼ scale so forth and so on. Even though you know how to use CAD software to design and draw the airplane, without considering the aerodynamic principles, you won’t have a stable airplane. So this is the first step on how to fly scale model airplanes. It will be impossible to fly your scale model airplane without considering the aerodynamic design. Again, before you attempt to build & fly your very first scale model, you should have already build your skill to at least an intermediate level. Meaning, flying a non-scale shoulder wing design type of model airplane. Then choose the trainer type full-scale model airplane like the Cessna 150 or J3 Piper Cub.
At least those airplanes have a built-in stability design. The wings constant chord and rectangular (for J3 Piper Cub). High wing location, meaning the wings is above the fuselage, which have pendulum stability. Landing gear is tricycle type (for Cessna 150). But wait, does this mean the stability is the same when you scale down those airplanes? The answer is No. Those airplanes will fly terrible when you scale it down and copy the exact dimensions. Like what I’ve mentioned previously, the aerodynamic design should be considered. This phenomenon is known as ” The Scale Effect”. You can’t scale down the air molecules & the viscosity of air. The behavior will be different. The wing location & wing area, horizontal and vertical stabilizer area & location, airfoil design, plays a major role on its stability.
Redesigning the airplane is essential. The model has to be redesigned based on the lift and drag coefficients and Reynolds number on its miniature dimensions to achieve stability. This is why some Almost Ready to Fly, Ready to Fly or Kits have 30% or 40% scale specification. Meaning only 30% was copied from the full size airplane. Possibly the horizontal stabilizer area was modified or vertical stabilizer. Changed the airfoil type or wing area. In order to achieve stability. The closer its size to the full size airplane, the more you can copy the exact dimension and behavior. This is why ¼ scale model airplanes are popular to those really serious on RC airplane modeling. Considering the cost and set-up, danger to life and property, it will only be possible for those who were well to do. Imagine how many gallons of fuel it will consume! You will also need bigger flying field. Good thing that gas or petroleum engines (chainsaw engines) are fit to use in those monsters which reduces the cost of fuel. Unlike using methanol, castor oil and nitromethane for fuel on glow engines.
So before having any expectations on acquiring one, first consider those facts.