Originally Posted by PeterVRC
Well that theory/maths seems right.....
But all I SEE is that (clearly on prop aircraft) more CFM, thus more thrust (measured statically to test) does not equal more speed.
So what that seems to really mean is that maybe YES thrust is efflux related... but the end result in a plane's SPEED is not. Sort of 'thrust is not thrust'.... but more depends on HOW that was created.
eg two fan design of equal thrust will not fly the plane the same - like the props, one type's THRUST is torque based, and the others is airspeed based.
So I can see and go along with that view on it....
It still means you need more power for a CS10... IF you want equal SPEED.
You aren't going to SEE that. It is not a chalk and cheese change. What is 5% out of 100kph??? 5kph. Try to SEE that in flight! LOL
Though I think it is more towards a 10% speed difference (from equal power).. Even that would be hard to SEE.... you need proper measurements, and even those are hard (as mentioned) as there are so many other variables per flight (wind, battery etc)... so you certainly could never tell much by SIGHT.
Though over a longer term average on my Meteor, I have worked out that it is slower with the CS10. (close to exact same power in static tests). But even that has tolerance range, because you HAD to use a different motor for the CS10... adding another variable of a slight unknown change.
Do tell us from your engineering background what is the proper way to calcuate the fan thrust?
So far you have only touched on what you feel, let us know how you calculate thrust?