Hi guys, It is an unsual question and I am a Beginner so go easy on me. I'm still at the early stages of learning all about rc planes and ideally I would like to build a F-22 with two turbines in it. I'm having a hard time figuring out the approx. max air speed of the plane assuming each turbine produces about 80lbs of thurst (combined thrust 160 lbs). Can anyone please tell me how I can do this?

Note: I know the airframe & weight matters a lot in determining the max air speed, but the problem is I can't even find a formula in which I can plug my values in and it will give me theoretical max speed.

If you want to learn how to do this, go to college, get a degree in aeronautical engineering.

Seriously, there is not a simple plug in formula for this. There are so many factors in the shape of the plane that contribute to the drag of the airframe, including air temperature, humidity, and altitude (air density). Essentially, you reach top speed of the aircraft when the forces of drag equal the thrust output of the engines. Calculating the theoretical drag of the airframe is the hard part, and is usually done with fairly advanced computer simulations.

Brad

I'd like to know where you're going to find model turbines that produce 80# of thrust. 20 - 3- pounds is average for what's on the market and 45# is the biggest I'm familiar with.

And since the average F-22 would weigh in at 20 - 30lbs, having 160lbs of thrust would be VERY fast - at least for a few seconds, then the wings and tail surfaces would be blown off just seconds before a terrific crash.

I used to have a software program for rockets, when I was into high power rocketry.
It would calculate CG as well as speed at any given point in flight and expected altittude and was reasonably accurate when compared to the results from my onboard equipment.
That was a complicated software program based on simple strait forward rocket designs and complete known thrust curve data from the motors.
An airplane is much more complex and would require an even more complicated program to calculate.

This subject is WAY past the scope of the Beginner's forum. I'm going to close this thread down, but leave it in place. I would suggest that if you are still looking for the answer to your question that you ask it over in the Jet's forum.

Ken