Angle of incidence

[Darthwonga]

Is there any way of calculating the angle of incidence of a model's wing? I'm currently in the later stages of finishing a design for a aerobatic/3D beasty heavily inspired by the Funtana S 90 and the full-size Katana. The only thing that I'm not sure about is what the wings angle of incidence should be, given that it has a symmetrical wing section. Is it possible to easily calculate the correct angle of incidence, or is it more of a rule-of-thumb kind of thing? How dependent is the angle of incidence on the precise wing profile? Does the tailplane profile make a difference?

Cheers for any opinions / input

DW

[Ollie]

The purpose of incidence is rigging on the work bench. How the plane flies depends on:
1. CG position within its range and pilot wanting pitch stability.
2. The angle between wing and stab. is long. dihedral (decalage).
3. The thrust line between and wing and stab.

These three adjustments result in trimmed flight and mainly not the fuselage center line.

[capncrunch]

2. The angle between wing and stab. is long. dihedral (decalage).
3. The thrust line between and wing and stab.

Oillie, wouldnt getting the incidence of the wing right go a long way towards #2 and #3?

-b

[capncrunch]

oh and to the OP. its a 3d plane, you want it to fly the same in all directions (well, in all opposite attitudes), you cant go wrong with setting the wing centerline paralell with the thrustline.

[Darthwonga]

oh and to the OP. its a 3d plane, you want it to fly the same in all directions (well, in all opposite attitudes), you cant go wrong with setting the wing centerline paralell with the thrustline.

I really should of thought of that shouldn't I? ;) Keeping the whole lot parallel is also the easiest option in terms of construction, so I'll try that. I can always fiddle the angle later by shifting the rear wing joiner tube up or down.

Cheers for the quick feedback - will be ready to start shredding balsa by the weekend :D

DW

[marfish]

Also, you might consider that it seems that drag-induced pitch on a high wing and low tail is balanced somewhat by a thrust line somewhere in between them and closer to the wing centerline due to higher drag from the wing. The reverse would be true(low wing-high tail). It would also be balanced by some incidence angle. Take all the effects of drag and try to balance them to the thrustline. If the longitudinal center of mass is also along the thrustline, great. Pattern planes generally have wing and stab very close to both thrustline and centerline of mass.
Marlan

[dusty IV]

I see your question got a bit of the run around. New designs are a bit empirical but try 0* or maybe +.5* for the wing compared to the stab. Your elevator can compensate for any error with in reason. Be prepared to cut the elevator loose and readjust if you have to hold constant up or down.

I have an incident checker I think is made by Great Planes. I didn't like their analog meter readout so bought a digital level that fits on the Great Planes jig. This replaces the analog meter and makes set up and readjustment a piece of cake on new designs.

I sometimes notice on this site that sharp shooters seem to like to show how smart they are by asking more more questions and confusing the issue instead of just giving an answer or staying out of it.

Anyway got my beam question answered by simply building a model beam and testing it. So much for theory.

[capncrunch]

I sometimes notice on this site that sharp shooters seem to like to show how smart they are by asking more more questions and confusing the issue instead of just giving an answer or staying out of it.

AMEN to that! drives me nuts sometimes.

-b

[RCAV8R13]

The purpose of incidence is rigging on the work bench. How the plane flies depends on:
1. CG position within its range and pilot wanting pitch stability.
2. The angle between wing and stab. is long. dihedral (decalage).
3. The thrust line between and wing and stab.

These three adjustments result in trimmed flight and mainly not the fuselage center line.
Ollie,
I have never heard the angle of incidence between wing a stab refered to as dihedral, decalage certainly, but not dihedral. Is this an old expression? Differential aileron is sometimes refered to as "gearing" or "Scheduling" the ailerons.
RCA