Well, if models are used for testing and design in the development of a new aircraft, I presume that will be the closest scale model of the final full-size aircraft.

But, none of that was the reason for this thread. I truthfully just wondered if there was a "rule book" somewhere of all the various classifications so I could just educate myself. The question popped in my mind initially when I found folks speaking of over size .050 in the 1/2A section and whenever I saw that an airplane over 80" wingspan (single wing) was IMAA legal. I realized I was ignorant of the various classes and began to take notice as I perused the various kits and ARFs now available. I knew some of this was more of a knowledge via familiarity for a lot of flyer but I thought that by chance there might just actually be a published concise listing that bulletpointed all of the items used to qualify an aircraft (or disqualify) to a class or group.

Right now it almost appears there's really only an "open" class unless a particular field has its own adopted rules the participants mutually observe. Surely that's not the case?

Regards,

Clay