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,

"jan olieslagers" wrote in message
...
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,

Don't know if this will help you. It is mainly about scaling down
wings--

http://www.nurflugel.com/Nurflugel/n...eory_basic.htm

--
We have met the enemy and he is us-- Pogo

Anyolmouse

jan olieslagers wrote:
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,

Scaling rules are usually presented as dimensionless ratios in order to
free them from any nominal size parameters. There are plenty - perhaps
50 common ones, but not all apply to aircraft. You are certainly
familiar with one called Reynold's number. I took a quick look for my
poster dispaly of these ratios, but can't put my hands on it presently....

Brian W