scaling formulae

I seem to remember seeing formulae for scaling planes, but cannot find
them back. The one I do remember is "power required rises to the third
power of airspeed" - so to double the airspeed the engine power must go
times eight.
But there must be the same about weights and dimensions - if I double
the length and wingspan, empty weight goes up by so many percent and max
gross up by so many. Any pointers, please?
NB of course I am aware that such factors can only be estimates, there
being very many other parameters.
TIA,