This morning I was experimenting with how much lift wings produce based on their angle of attack, testing different aerofoils. Here are my findings.
To test, I used wings on a rotator that rotated by activators. Ie, activate 1 will rotate it 5 degrees. Adding activate 2 rotated the wing an extra 5 degrees, getting a 10 degree AoA, and so on. The wing was placed on a long spring, with a measured next to it, which had an arrow connected to the top of the spring that measures how much the spring is stretching.
Wind was set directly down the runway at 100mph.
The contraption looks like this:
Each block on the measures counts as 1. Angle of attack was measured up to 40 degrees.
Here is a graph of the results
What these findings show
This shows that, generally, wings (other than NACAPROP) behave very similarly below about 14 degrees of Angle of Attack. This is really interesting because it means that, really, the choice of aerofoil doesn’t matter if you’re not stalling in your plane.
The one thing that separates the aerofoils the most is their stall characteristics.
NACAPROP seems to be in a permanently stalled state, but at high AoAs, it creates more lift than the other aerofoils. Also control surfaces never stall on NACAPROP foils, which makes them really useful.
Flat bottom seems to have a gradual stall, and generates lift up to a really high AoA. It makes the most lift at about 27 degrees. The stall is very gentle.
Semi-symmetric wings generate the most typical kind of stall. They stall at around a 17 angle of attack. The stall is gentle and lasts up to about a 25 degree angle of attack.
Symmetric was the most interesting for me. Some kind of buffet simulation seems to happen between 14 and 20 degrees.
Doing some further tests, these aerofoils really do seem to buffet. I never knew that! That’s super cool!
Ya know, wing physics in SP are way better than people give them credit for.
Here's a more up-to-date version made by bagonegg
Check this out @CptLiar
@jamesPLANESii
Okay thank you!
@ToeTips For alierons and elevators, you should use the default control surfaces. In real life, the control surface affects the airflow over the whole wing, not just the flappy bit. If you make them out of a seperate wing, the main wings and control surface have no idea the other one exists, and the main wing and control surface are fighting against eachother and you get an insane amount of extra drag and the control surface can stall abrubtly at rather low deflections, which isn't realistic and is very bad.
For flaps, I'd still make the main wing section have a control surface, but I'd also add a wing in the control surface which is flat bottom, which simulates the change in the centre of pressure of the wing, and also adds extra drag. I'd also add an airbrake in the flaps too
Rudders yep
@jamesPLANESii
Okay what about flaps and Ailerons? Do I go flat bottom? And I assume symmetric for rudders.
@ToeTips Yep that looks about right
@ToeTips When the airflow starts to separate from the top of the wing and becomes turbulent, it's called buffeting
Okay so basically,
If making a realistic handling jet:
Semi symmetric for the main wings
Symmetric for the stabilators
Flat bottom for the slats?
Whats buffet?
save4later
@jamesPLANESii Gracias!
@CptLiar Oh gee. Not sure why. Not sure how I'd fix it either since I can't find the picture again. I jave something else for you though. Hold on
Hi @jamesPLANESii
This post is very helpful, but link of the graph is down atm (table is still alive).
Could you help to restore it?
Thank you
Another thing to note here is the amount of drag created by each airfoil, which isn’t represented directly by a graph here. Usually, an airfoil’s performance is represented by 2 curves, known as the Lift/Drag curves, or L/D. However, you can indirectly infer the amount of drag created by the amount of lift created…the more lift created, the more drag is created, always. This is important as one can demonstrably see that the symmetric airfoil creates far less drag at higher speeds than the other two airfoil shapes.
This is cool and very useful. I did some research on how combining airfoil types affects these results using your wing testing contraption that I'll make a forum post about.
the Flat Bottom airfoil graph looks a bit like a highly swept wing with vortex lift
@JoshyR8 Maybe, but that might produce more drag than having more wing area at a shallower angle too. I'm not sure
If I reversed this e.g. -27 degrees for a flat bottom, is that optimum downforce?
@JamesieMcPlanesieThe2st ok thanks
@UltraLight Yeah the propeller aerofoil
btw what is NACAPROP? A propeller?
Very interesting! I never got a buffeting effect but still great!
a mathematical method to calculate lift?! unheard of, Ever!
@Dad Thx :D
Here! :) @MethaManAerospace