F86_SABRE

OK here is one for the list:
I am browsing this scale drawing and noticed that the elevator stab has a 1.5 degrees negative incidence (to clarify - the leading edge is pointing downwards). Presumably the aircraft will have a tendency to lift the nose. The aircraft in question is the Pilatus PC-21. I do not know whether the wings have positive incidence, presumably yes. The engine is pointing 4 degrees down and 3.5 degrees side thrust (to starboard).
Question:
In this case of r/c planes would one introduce such a feature of having a negative incidence on the elevator stab if one maintained the same engine incidence of 4 degrees? Is it advisable to emulate or should it be 0-0 type?

Your contributions will be most welcomed.

With thanks

Reuben

TedMo

If your plans show 1.5 degrees negative on stab I'm curious why it would not indicate wing incidence? The 4 degrees the engine is down is not wing incidence that is engine downthrust. I'm at a loss as to why they would provide those 2 bits of info but ignore wing incidence? If decalage is stated that is the angle difference between wing and stab. Perhaps the wing is automatically fixed by the manner it's mounted.

F86_SABRE

Thanks for your input.
I am sure that the wing does have incidence. I calculated it to be around 2.5 degrees. It is not shown in the scale drawings but the other important bits are shown. I am mostly after the effects of having 4 degrees engine inlination and 1.5 degrees elevator stab offset on an r/c plane. Bear in mind that the original plane does not have any problems to fly!

Reuben

rmh

full scale setup is not same as a model setup

don't even try to "calculate" the correct setup
basically try to find the zero lift chord line for th wing - and set the wing and stab RELATIVE to each other by - say - a degree. (leading edge of stab slightly lower than hinge line of stab.)
One degree is aprox 1/4" in one foot.
close enough for folk music.

F86_SABRE

Thanks for the reply Dick,
Whilst that makes sense I wonder whether the 4 degrees negative engine incidence would really effect the flight performance of the plane if one had to make a 0-0 elevator stab. Otherwise one would have to "cheat" with adjusting the fuselage nose, thus somehow altering the look of the plane. Probably the latter would be a necessary evil.

Thanks again.

Reuben

rmh

Set the engine to look scale in angle - - a litle downthrust won't harm any thing on that design
zero zero setups are best for very light models which are aerobatic
for a nice scale cruiser , a lil bit of decalage will be fine
of all the adjustments you can make to trim - downthrust is the least effective.
The relative angle between wing and horizontal stab is the most effective.