scaling formulae

[jan olieslagers[_2_]]

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,

[Anyolmouse]

"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_o_d/oldstuff/html/theory/theory_basic.htm

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

Anyolmouse

[Brian Whatcott]

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