Airfield Models Formulas use with Flying Model Aircraft

How To Calculate the Distance to Offset an Engine to Account for Thrust Settings

May 05, 2015



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Airfield Models (http://www.airfieldmodels.com/)Calculating Engine Offset

Most model aircraft designs have a certain amount of down and/or right thrust.  The back of the propeller should be on the centerline of the fuselage when viewed from above and on the thrust line when viewed from the side.

If the model you are building has a thrust adjustment and you center the engine mount on the intersection of these two lines then the propeller will be in the wrong place.

See the Trigonometry page for more details.

This problem is very similar to solving for dihedral.

 
 

The back of the propeller should be located on the thrust line.  Therefore, the engine must be mounted off-center on the firewall if there is right or down thrust.

In this example we are going to say that the back of the propeller is five inches from the firewall and the right thrust is 4.  The next image is exaggerated to make it easier to explain the concept.

Use Trigonometry to convert the angle to a measurement.

= 4

Sine 4 = 0.069756

Plug in the number you just calculated to find the opposite side of the triangle.

0.069756 = Offset 5"

Offset = 5" x 0.069756

Offset = 0.34878 from center or approximately 11/32"

 
 

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How to Find or Calculate the Mean Aerodynamic Chord (MAC) of a Wing
Calculating Speed and Propeller Efficiency

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Copyright 2003 Paul K. Johnson