Maybe the best definition so far, from my point of view is what YOADRIAN has stated above. Anyone who would call themselves a Master Builder could never be one, in my opinion, as a part of being a master includes a humbleness, which would never allow someone to think so highly of themselves. I also don't think, because you build model airplanes professionally, makes you a master builder. There are people who are prolific builders of junk; or, can simply build "good enough" airplanes very quickly. This is not a statement that Master Builders can not be professional builders!

Since we've been asked to define what makes a Master Builder, from my point of view, they would be found in scale. This is where the builders art is put to the strongest test. Of course different people will put the emphasis on their chosen endeavor, which is natural.

If your looking for someone to build an airplane(s) for you, simply look at examples of their work, both in the air and on the ground. You don't require a Master Builder to do this. Define what the venue is your focusing on. If your interested in Scale, you really can't use a builder to compete, as you must be the builder of the plane, unless your interested in a team event. If your interested in aerobatics and you want someone to build an IMAA or pattern airplane for you, ask to see some "works in progress" they are currently working on, as well as how their creations look in the air and on the ground.

However, I would turn my back on anyone who calls themselves a Master Builder. It's anyone other then themselves job to state such a thing.