When ever you test fly an airplane, especially biplanes, it is really important to get the incidence (angle relative to the fuselage centerline,) for both wings and the horizontal stabilizer correct. Most scratch built designs will have this all important information on the plans and with kits, it will be called out in the instructions.
A great tool to measure and set these incident angles is the new digital “Angle Pro” angle meter from hangar 9. Check it out when you get a chance. Years ago, the king of angle meters was the Robart incident meter that used a weighted indicator needle and a printed scale. But the new “Angle Pro” sets a higher standard, is easier to use and, it is accurate to 1/10th of a degree.
It comes with an aluminum incidence bar and two self-centering alignment brackets. It also comes with a engine thrust attachment. It also comes with a seperate attachment clamp so you can check the angle of deflection for your control surfaces. This is ideal for giant scale 3D aerobatic planes.
We’ll be shooting a how to video using this digital meter at the flying field for the MAN website, www.modelairplanenews.com so stay tuned!
- Check and or calibrate the Angle Pro Meter (see instructions)
- Assembly your plane and place on workbench
- block up the tail, and check fuselage alignment. (most airplanes will have a cockpit floor that is set at 0-degrees)
- lift the tail until the cockpit floor is set at zero.
- place meter on the horizontal stabilizer and check angle. Most biplanes will have a reading of zero or positive 1 degrees. (make sure it as indicated on the plans.
- Place the meter on the bottom wing and check reading.
- Place meter in top wing and check reading.
For most positive stagger wing biplanes, the top wing (forward of the bottom,) will be set a degree or two more positive than the bottom wing. This way when the top wing stalls before the bottom wing, the nose of the plane will want to drop naturally.
So in a typical setup, the fuselage is set at zero, and the horizontal stab will be 1 degree positive. the upper wing will be at 1 degree positive and the bottom wing will be set at 0 degrees. Always check the plans for your plane and set the angle accordingly while building.
If you have to make adjustments to a plane already built, set the plane up with the mentioned readings and use washers or shims to adjust the wings’ incidence readings.