thrust line

[Beginner!?]

hi

sorry if i am asking an stupid question

but what THRUST LINE is exactly?

how do i can determine and figure it?

what is the relation between it and wing & tail position?

thanks for any input

Beginner

[Scaledown]

The thrust line is the line of the prop shaft.
Check out the post by Ron Daniels in this thread for some good info on thrust/wing/tailplane angles: http://www.rcgroups.com/forums/showthread.php?t=332257

[Beginner!?]

thanks for the link i will read it today

Beginner

[Beginner!?]

i read that link but it couldnt help me at all

does anyone can help and give me a direct answe please?

thanks

Beginner

[globemaster3c17]

Imagine a line drawn directly through the center of your prop hub and parallel to the crankshaft. This is the thrust line. If you have zero down thrust and zero right thrust, then this line will also be parallel to the longitudinal axis of the airplane. Moving the thrust line up or down will cause a change in the relationship between throttle and pitch change. Normally a stable plane will raise it's nose when you apply throttle, but that isn't normally a desirable characteristic for R/C flying. Among other things, you can raise the thrustline, which will cause a pitch-down moment. If you get the pitch-down moment the same as the pitch-up moment from the aircraft's stability characteristics, you can go from gliding at idle to cruise at full throttle while maintaining a level flight attitude. I could probably draw a few simple diagrams if my description doesn't quite do the trick for you.

[Beginner!?]

thanks for your help

but if the thrust line for an airplane isnt uiltable and in good position then what will happen?
does the plane will droops with its noise?


what is relation between the thrust line and wing and tail position?

[globemaster3c17]

Well if the thrust line is not in an ideal position, then an attitude change would occur with a change in throttle setting. If you mount the engine up too high, then the plane would pitch down when applying throttle, mount it too low, and the plane would pitch up with an increase of throttle.
I'm sure there are other things that I can't think of concerning thrust line and position of the wing and tail. The things I can think of deal with controlability. If you mount the horizontal tail in the typical location, then you will have more control authority at low speeds and high power settings because the airflow over the tail is a combination of airspeed and propwash. Yet if you made a high T tail where the horizontal tail surfaces are out of the propwash, then you wouldn't have much pitch control at low speeds since the only airflow over it is due to airspeed.

[Beginner!?]

ok thanks for your great input