I am trying to understand wing_thickness_ratio and how it’s expressed? My
original assumption was it was the airfoil thickness ratio express as percent
over 100. If we use a NACA0012 airfoil as example it has a thickness ratio of
12(0.12 in the cfg), which ends up with a very THICC “wing” element. If we
check the documentation:
https://docs.flightsimulator.com/html/Content_Configuration/SimObjects/Aircraft_SimO/flight_model/geometry.htm
it states:
The wing local thickness, calculated as: localchord(x)* wingthicknessratio
where: x=lateral chord
Value is in ft.
Given their fomula and solving for the thickness ratio thickness ratio = local
thickness / local chord thickness ratio = 12/100 thickness ratio = 0.12 Which
is our AirFoil Thickness, however when viewed in the Sim with Sim Forces
debug, the green dots do not align with the wing surfaces and there is quite a
lot of free air between the surface and the dots. If we review the “tutorial”
on creating a flight model:
https://docs.flightsimulator.com/html/mergedProjects/How_To_Make_An_Aircraft/Contents/Files/Flight_Model/Geometry.htm
it states:
Next you can set the Thickness Ratio of the wing in the Geometry panel. This is a ratio of the wing size and most wings are between 2% and 5% thick. In the CFG file, this is the wing_thickness_ratio parameter .
There are many many aircraft out there using airfoils with thickness ratio
well above 5% so it must mean something else. During a discussion on our
discord, one of our members thought perhaps that it is the % thickness ABOVE
the camber line.
Maybe they divide by 2. and they mean the thickness is from the camber line to the top of the airfoil. then 0.05 would be 0.10 (10%) getting closer.
If we continue with our NACA0012 example this has a 0 camber so runs through
centreline and the thickness would then be expressed as 6% (thickness -
camber) / 2 (12 - 0) / 2 = 6 This appears to be closer to what is requested.
If we use something a little more exotic with say a 12% thickness and 1.5%
camber: (12-1.5)/2 = 5.25% Unfortunately all of this is just guessing. So how
do we reliably calculate wing_thickness_ratio?