7.7: Scaling / Change Size of whole Airplane
Now and then one has a case to change the size of an airplane true to scale,
for example if one plans to build a man-carrying airplane to scale.
The easiest way is to enter the original dimensions and to carry out a
full-scale reduction. In the following a function is described, which makes
this possible.
Click the button 'Scaling' to open a new window.
In the upper input field the actual span of the largest wing is displayed. In
this field you can directly enter a new size and confirm with enter. The entire
airplane will be changed according to the factor wingspan old – wingspan new.
Near the input field are Up/Down-buttons located. They can be used to change
the span of the largest wing with mouse clicks.
A click on the right mouse button pops up a menu to set the increment between 0.00001m
and 1m.
The second input field offers a possibility to change the scale on a percentage
basis. A value of 50% leads on to a halving while a value of 200% leads to
doubling of the airplane's size. The entered value must be confirmed with the
button 'Apply'.
Near the input field are Up/Down-buttons located. They can be used to change
the percentage value with mouse clicks.
It is possible to change the mass of the airplane automatically if desired.
Tree options are available.
1) 'Mass unchanged':
No change, the mass values of the original construction are taken.
2) 'Adjust Mass linear':
This option changes the mass accordingly to the change in size. Halving the
size will lead to halving the mass, doubling the size will lead to doubling the
mass.
3) 'Adjust Mass to square':
The scaling factor is computed with the formula fak = wingspan_new /
wingspan_old.
The new mass is computed with the formula mass_new = mass_old * fak ^2.
Example: Given is an ultra light aircraft with 15m of wingspan and a mass of
400kg.
We plan to build this airplane with a wingspan of 1.5m.
The scaling factor is fak =1.5m / 15m= 0.1;
we calculate 400Kg * 0.1^2 = 4kg.
With a wingspan of 1.5m and the same design-Cl our model would fly with the
same speed as the original ultra light aircraft.
The scaling function adjusts the masses of the wings as well as the additional
masses.