ORIGINAL: da Rock
And both methods offer a subjective valuation of their loading figures. So neither really can be 'wrong.'
I've often wondered if the aeronautical engineering community has ever offered an opinion of how well the cubic system works in practice. Wondered how alike a small model flies compared to the larger one when they both have the same volume. Like stall speed, load carrying etc.
BMatthews might know about that????
I'm not BMatthews (never even played him on TV) but as a retired NASA aero engineer who worked in part with scaled down models in aerodynamics research, I'll weigh in.
The short answer is yes, this issue has been studied and discussed at length. And the second short answer is no, there aren't any scaling methods that exactly duplicate the full size counterpart in every respect. But for research purposes, it is sufficient to understand the differences and account for them. For model flying, the issues are different. Do you want the airplane to fly at the same speed, or do you want it to fly at what APPEARS to be the same speed ? Do you want the time for a 360° roll to be the same or do you want the distance travelled during a 360° roll to be the same ? Do you want the diameter of a 60° banked turn to be the same, or scaled to the size of the model ?
There are always differences when you scale down a plane. You can adjust the weight (density) to achieve the effect that you want, but something will be different - speed, angular rotation rates, distances travelled, etc.
The only scale size that makes all parameters come out exactly the same is one-to-one. That's not to condemn scale models; you just have to accept the differences and optimize them for the image that you wish to project.
Dick Fischer