Magne,

What Dick said is mostly true; there are some models that might not follow the exact word of the rule. I can think of a few "scale" aircraft that have the horizontal stab lower than what would be a ten percent displacement of its real world counterpart. But the intent of the rule was to give model aircraft manufactures and designers a guide when building new offerings.

It all comes down to this, in a perfect world where everyone follows the rules to the letter; all IMAC aircraft would have their flying and control surfaces within 10 % of their scale location. The length, width and shape of the fuse would also be within 10% of the full scale dimensions.

Again the models scale is determined by the wingspan, so if your wingspan is 100” and the full scales is 333”, you are 1/3 scale. Now all of the other dimensions should be less than a 10% deviation of scale. As an example, lets say the 1/3 scale length of this same full scale aircraft is 90”, legally you could add or subtract 10%, (up to 9”) to the fuse. A ten percent deviation of all other dimensions except wingspan could be done as well. Remember, wingspan determines scale; a change in wingspan is a change in scale.

Hope this makes sense,

Tom Wheeler