Scaling of an existing model for the AeroFly Professional

1.
Scale geometry file OBJ

The first step scales the geometry of your model.

Use the tool zoomAFP of Rainer Stein for this operation: 31.03.03 ZoomTool


Calculate the scale factor for your desired size:

desired wingspan devided by actual wingspan

desired wingspan 2m / actual wingspan 3m = 0.67

The tool only works for OBJ files, so you can't use it for the original AFPD TGO files.


For all further operations, use WORDPAD or an equivalent editor.
Notepad and WORD are NOT appropriate.


2.
Coordinate-Adjustment in the TMD file

All joint coordinates and all pivot points of the objects have to be scaled as well. Use the same factor (example 0.67) for calculation.


Find joint coordinates in the line R = ...

cd JointFuselageTailGear/
X    = tmvector4r(   1.0000,   0.0000,   0.0000, 0 )
Y    = tmvector4r(   0.0000,   1.0000,   0.0000, 0 )
Z    = tmvector4r(   0.0000,   0.0000,   1.0000, 0 )
R    = tmvector4r( -0.9379,   0.0000, -0.1379, 1 )


Find pivot points in the line MountingR = ...

cd TailGear/
MountingR = tmvector4f(  -0.9379,  0.0000,  -0.1379,  1.0000 )


Attention: Modify only the first 3 values:
first value  = fuselage axis, positive to nose
second value = wing axis, positive to left wing
third value  = heigth axis, positive to top


3.
Weight adjustment in the TMD file

All parts should be modified to reflect the new size.
The weight is always set in the object section of the TMD.
Also set min/max values to appropriate figures. Don't use a difference between min and max more than factor 10.

cd LeftWing/
Mass = 0.75
RangeMassMax = 2.0
RangeMassMin = 0.2


4.
Span adjustment of the wings

The actual wingspan will be automatically calculated from geometry.
But you MUST make sure, your min/max range covers your actual span. Otherwise you will not be able to adjust this. Do this step for all wings and stabilizers.

In our example we have an desired span of 2m, which is a half span of 1m.

cd LeftWing/
RangeSpanMax = 1.5
RangeSpanMin = 0.5


5.
Adjustment of the binding forces and dampers of objects

Due to the modified pivot points and weights we have to set the new parameters.
This is a critical point, because without adjustment your model will not work properly.

cd JointFuselageLeftWing/
Kf = 100000
Df = 500
Ktx = 10000
Dtx = 100
Kty = 10000
Dty = 100
Ktz = 10000
Dtz = 100
MaxForce = 1000
MaxTorque = 1000
Rigid = 0
Essential = 1

For a first trial you can set all joints to rigid = 1.
Later you have to set at least the gear joints to rigid = 0.
Otherwise your model will dance on the ground.

To adjust the forces (K-values) and dampers (d-values), you may check the parameters of a model with similar size and weight. The forces and dampers depend upon the pivot points and the weight of the related objects. All of the related objects must have a weight greater 0.

If parts of the model fall to the ground, the forces are not high enough.
If the model implodes and all parts wobble around, the forces are too high.

To adjust these parameters, you can use a feature of AFP/AFPD:
Start the sim in windows-mode, not full screen. Contemporarily open the TMD for editing. If you modify your values, save your TMD file. Then press Shift-F12 to reload the model to the sim. Therefore you don't have to leave and restart the sim.

You don't have to adjust the following joints, because they're always set to rigid = 1:

cd JointFuselageEngine/
cd JointLeftGearLeftWheel/
cd JointRightGearRightWheel/
cd JointTailGearTailWheel/
cd JointFrontGearFrontWheel/


Note 1:
Essential = 1 causes a restart of the model, if a part of it crashed.
Essential = 0 allows you to experiment with 1 wing or 1 gear left.

Note 2:
MaxForce = 1000
MaxTorque = 1000
If the K- and D-values are rather high, you will get a stiff connection of the parts. This is absolutely correct for many aircrafts. But in this case they will be extremely crash restistent and hardly break apart. Therefore you can give a separate crash factor with MaxForce and MaxTorque, which is generally lower than the K-forces.

MaxForce = 0
MaxTorque = 0
If these values are set, the K-forces are also used for calulating the crash resistance.


6.
Finally Use the internal model editor to adjust more values like profiles, angles and all that stuff AFTER you finished TMD editing.