RE: Twice the scale, now how about the motor?
Lnewqban, thank you.
BMathews is right to say that designing for purpose, from scratch, should produce the better model.
But as I understand it we started from "I like my Super Wotnot, I want a bigger one, so how much power etc??"
HighPlains. That is true, the things that do not change with size though are the coefficients. That why they were invented so why not use them? That's why in my spreadsheet I assumed that the aerodynamics would be copied, lift coefficients would be the same regardless of size and drag coefficients would increase a tiny bit as Reynolds number reduced &vv.
This should produce a model that is "in character" with the original.
Some day I'll go public with my Model Resizing spreadsheet.