ldmfa.com

In days of yore, my modelling budget was a pittance. Scratch building my own control line aircraft was the only way I could afford to fly. RC for a 15 year old on a pocket money budget was a distant dream. By building what I flew, I learned what worked and what didn't….the mates and I would often sit down on a rainy weekend and "invent" a new aircraft on the board with nothing but the motor size to start. It wasn't all that hard  once we had worked out the "formula". In fact, I resurected these skills a couple of years back and knocked up "XX", a small C/L profile aircraft you may see me fly from time to time.

Through trial and error (and pouring over the magazines of the day) we had worked out the best  wing size we needed to fit the engine we wanted to run (generally an OS .15 or .25). From that, we could work out the fuse length, and tail feathers, the whole lot just fell into place. The details of the formula I can not remember but, we had built so many, I think we stopped using it directly ourselves. In the end, we knew that we just had to make it look "right". One of these formulas existed for RC when we were doing our own thing, because I remember seeing it in a mag…..and, after some searching, I have found and attached below something very similar. This one is in ft/in but its the ratios that matter.

For anyone starting out, and for those with a building bent, this "formula" is a practical framework for just about any sport or trainer aircraft. Even if the idea of hacking balsa is not your thing, I am sure this will help everyone understand their aircraft a little more. Boomerang owners that take a few moments to compare their model with this general formula will find that the aircraft follows these parameters almost exactly.  

If your like me and have "many" wings left from ARF crashes, you could use this formula to make a new aircraft by building fuse and tail feathers from scratch, and be confident that it will perform reasonably well. If your thinking of doing that, just drop me a line, I would be happy to lend a hand!