Great Planes GPMR4020 User Manual

P.O. Box 788 Urbana, IL 61803 [phone]

www.greatplanes.com

Congratulations! You are now the proud owner of a precision incidence measuring tool. The Great
Planes Accu-Point™Laser Incidence Meter is accurate to within 1/4º. This allows you to set-up and
check your airplane with a degree of precision that was never before possible.

Why use an incidence meter?

Model airplane designers create aircraft with specific performance goals in mind. The airplane’s spec­ifications and angles are set and verified thorough extensive testing and measuring to achieve their
design goals. When building a model airplane from a kit, you are, in effect, making a duplicate of a
model that was built and tested by an experienced design team. It is up to you, the modeler, to make
sure that the airplane is straight and true during assembly. If the wing incidence or engine thrust does
not match the design specifications, the airplane will not fly as intended by the designer. Many flight

prob­lems can be traced down to some kind of misalignment or twist between flight surfaces. Using the
Great Planes Laser Incidence Meter, you can easily pinpoint inaccuracies in your model and correct
them.

For the helicopter pilot, the Great Planes Laser Incidence Meter can be used to accurately measure
the pitch of the main rotor blades and to fine tune pitch curves.

Please read through the instructions and safety precautions to familiar­ize yourself with the proper operation of this tool.

INSTRUCTION MANUAL

© Copyright 1999 GPMZ0254 for GPMR4020 V1.0

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1. Attach the scale to the bar. The end of the bar should be even with the prop shaft

lug. The distance between the laser and the scale is important in order to achieve the
proper readings. This distance is always 20" [508mm].

ASSEMBLY

SAFETY PRECAUTIONS

1. DANGER: This tool uses a laser diode. A laser beam can be harmful to the eyes.

Do not look directly into the laser beam while the unit is turned on. Also, laser light,
when reflected off a mirror or similar reflective surface, can be dangerous.

2. This tool is NOT a toy. Please keep out of the reach of children.

3. When not in use, store the meter in the box it came in. The tool must be kept clean

for best accuracy.

4. The batteries included with the unit are long life cells. However, laser diodes require
a substantial amount of power to operate. If left on for extended periods, the batteries
will soon have to be replaced. Accu-Point batteries are available from your hobby
dealer (GPMR4022).

5. This unit is a precision measuring device with precision components. Do not drop
or abuse the unit.

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2. Install the batteries: The back of the laser unlocks for easy installation of the bat-

teries. Install the batteries noting the polarity.

3. Check the operation of the laser assembly. The weight and laser should rock freely
in the bearings. Adjust the left/right position of the weight block as needed for friction­free movement.

Congratulations, your meter is ready to use!

OPTIONAL LONG BAR INSTALLATION

If you have purchased the optional 36" [882mm] long bar (GPMR4021), the
laser assembly should be positioned so it is 20" [508mm] from the scale. If
not, the scale will not read accurately.

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The Great Planes Laser Incidence Meter can be used to measure the angular align­ment of various components of your airplane.

1. Stabilizer incidence relative to a reference point.

2. Wing incidence relative to a reference point (typically the stabilizer)

3. Wing/Stabilizer Twist: Use the meter to identify twisted areas in your wing or stabi­lizer. Typically this is referred as “washout” or “washin.”

4. Engine Thrust: Accurately measure the amount of down thrust or side thrust.

1. The first step in using the Laser Incidence Meter is to calibrate the scale to a refer-

ence line on your aircraft. This reference line could be the centerline of the fuselage,
your workbench, the wing, or more commonly, the stabilizer.

2. Position the meter so the grips are attached to, or in line with, your chosen refer-

ence line.

Note: It is good practice to position the meter so the scale end is towards the
back of the aircraft for all measurements. This way when you read the meter, the

numbers physically above 0° would be read as positive (+) and below 0° would be
negative (-).

Basic Meter Operation

Note: The best time to check your airplane is when it is in the framed up
stage of assembly since it is much easier to make changes at this point.

OPERATION