Thrust Line & Stabilizer Incidence
 

When the stablizer incidence is supposed to be ( 0 )zero degree incidence do we reference that to the thrust line? Once the stab...is set a ( 0 ) degree I then can adjust the wing incidence to the stab. Is this correct...thanks for any "light you can shed" on this subject for me.
Jerry

Datum
 

The stab incidence, the main wing decalage, and the thrust line are measured against the "datum" line. This is a line that travels down the center of the fuselage that when measured represents the fuselage having 0-degrees angle of attack and 0 degrees yaw. On some high performance gliders the datum line gives the fuse the appearance of being nose down, in most other applications it would be considered straight and level. Hope this helps. :)

Thrust Line & Stabilizer Incidence
 

cchs1964,yes that will work even if it doesn't match the datum line exactly, mignt have to adjust the engine thrust in trimming but usually have to do that anyway.
Have a goodun,John.

Thrust Line & Stabilizer Incidence
 

Thanks Outcast and TerrellFlyer...I have become more aware of the importance of incidence, datum lines, and it seems the more I thought about it the more confused I become...old age, I guess...
Thanks again...
Jerry

Thrust Line & Stabilizer Incidence
 

sometimes we tend to complicate the simple things ,taking the fun out of it,r/c flying and building is really fun.
Have a goodun,John.

Decalage
 

Incidence is measured against a datum line.

Decalage is the angular difference between the wing and stab.

Thrust Line & Stabilizer Incidence
 

Ed is correct, however decalage refers to the main wing only. If the stab incidence is 1-degree and the wing incidence is 1.5-degrees the decalage is .5 degree. The reason this is important is adjusting the stab incidence has the effect of changing elevator trim, adjusting the decalage effects the flight characteristics of the plane. Planes fly based on the lift generated by the angle of attack of the wing at a given airspeed. Since this is the constant changing the main wing decalage will change the thrust line, fuselage angle of attack, inverted flight performance and trim as well as a number of others. :^)