Computer Aided Design (CAD) for RC Airplanes
Learn to use a CAD program to draw plans for your next RC aircraft
Designing your own radio control model plane is something that everyone can do. Creating a model aircraft is a learned skill, and is a capability any modeler can aspire to. Employing computer aided design, or CAD, will greatly speed your model airplane design and plan drafting process. So let’s get started!
For those prototype aircraft designers with formal aerodynamics training there are any number of technical approaches that can be employed to produce an original model airplane design. For those of us without this sort of training, we can fall back on empirical methods to prepare an original RC model design.
Before you start to figure out the dimensions of your model design, you need to settle on the rough outlines of your project.
Details of the model’s design will come later as you refine initial sketches. But it is very important to put pencil to paper and sketch out, as roughly as you wish, the profile and plan view of your new plane.
Determine if you want a high or low wing aircraft, the location of the landing gear and the tail arrangement. These initial impressions are a starting point that we can and will alter with the use of CAD to prepare the initial and final aircraft plans.
Determine aircraft parameters
Once the aircraft outlines are started, the next step is determining more precise dimensions for the prototype model. I have devised a set of rules of thumb for determining aircraft parameters for a typical model. Start with a desired wingspan, and the remainder of the dimensions are easily calculated. Note that this approach will work for a “normal” aircraft, i.e. one with the motor in the nose section, a wing located near the middle of the fuselage, and tail surfaces located at the rear. For more advanced aircraft designs, such as a canard, these rules will not apply.
For a detailed look at the application of these rules to a model airplane layout, please follow my work with designing, preparing a plan and flying the Robin profile RC model airplane.
I employed extensive use of CAD for the Robin. As described in pages listing the characteristics of a typical CAD program, the inherent ability of a CAD program to always “know” the full size of whatever object is being drawn greatly facilitates the task of preparing a set of RC aircraft plans. It is very easy to alter dimensions, wing shapes or tail moments to adapt a first design approach to include improvements or changes discovered during test flights or prototype construction.
CAD takes the rather mundane tasks of drafting a plan, and through the magic of computers, instantly and precisely performs these tasks. It took a while for developers to figure out the best method to implement CAD drawing characteristics in a user-friendly format on a computer screen.
The first attempts at CAD for computers were hampered by the underpowered memory chips of the day and a lack of a practical user graphics interface.
All these challenges have been successfully resolved today. There are a number of CAD programs available for the home user. I have used TurboCAD for drafting RC plane plans since the year 2000 and am fully satisfied with its capability and ease of use.
The idea behind any model airplane plan is to present enough information on the plan itself for anyone to construct the aircraft. Model airplane plans were exclusively hand drawn until quite recently, when practical CAD programs became available for the home user. A CAD programs uses extreme accuracy in every aspect of its work. Lines are a precise length, circles an exact diameter, and bisected lines consist of two exact halves.
Preparing final plans with CAD
CAD makes the preparation of the final version of a model airplane plan easy. You can quickly arrange the drawing with fuselage and wing views aligned to best fit the printed final product. Annotating the final view with construction notes and information on wood sizes is rapidly accomplished.
As your recheck your work, it is easy to correct any mistakes found, and well as add additional comments. It is this freedom to make essentially unlimited changes to your final plan for your model that is such an attractive feature of mastering CAD.
It is certainly a bit of effort to learn the language of CAD, but an effort worth making. Once grasped, you will have drawing and design skills that will last a lifetime. Practice makes perfect. Your drafting and drawing skills will only increase over time with further RC modeling projects.
Author: Gordon McKay