Airfoils and Aerodynamics - A Basic Overview

Hi, I’m Tyler, from Perth, Australia. We recently learnt about aerodynamics and airfoils in school, and I thought it would be cool to give beginners a rough idea on how aerodynamics work, and how elevators etc. give you the ability to control the plane. By the way, I will probably make a few mistakes, so please don’t get angry at me if I say something wrong. Thanks so much to Colorex for making me the diagram of the elevator. The rest of the pictures are just off Google Images.

First, I’ll talk about airfoils and Bernoulli’s principle. Bernoulli’s principle says that the camber of an airfoil increases the velocity of the air passing over the airfoil. This means there is a decrease in the pressure of the air flowing over the top of the airfoil. The high pressure air on the bottom of the airfoil pushes the wing upwards. Here’s a great, but simple, picture showing how lift works.

Here’s a simple airfoil design. I’ve drawn some arrows and labeled it:

Here’s some high drag, low lift airfoils compared to some high lift, low drag airfoils:

Ok, there’s a basic overview on airfoils. I hope you now understand a little bit about how lift works. I REALLY recommend watching Flite Test’s Flite Tip on airfoils, and I also strongly recommend having a look at this site: http://www.allstar.fiu.edu/aerojava/airflylvl3.htm

Another cool fact is the propellers you use on your planes are ultimately just rotating wings. 

Ok, now I’ll do an even quicker overview on elevators and ailerons: two of the most important parts of those planes you have sitting in your shed (other than the rotating wings we call propellers). I won’t talk about rudders because I don’t know much about them, and don’t want to get it wrong. Elevators on planes are actually quite interesting, as they are technically reversed, which is something you don’t usually want. You know how when you pull your elevator stick down to go up, your elevator flap goes up, the opposite way to the stick? This is because the elevator is on the back of the plane. If the elevator was on the FRONT of the plane, like the Wright Brother’s first aircraft (I think it was on the front, anyway), it would go down. 

So, why is this? Because the elevator is on the back, it needs to tilt the NOSE of the plane UPWARDS. To do this, the BACK of the plane must tilt DOWNWARDS, so the flap goes upwards, therefore pushing the air up and forcing the rear of the plane downwards. In the Wright Brother’s case, when they wanted to tilt the nose of the plane upwards, the needed the elevator to pull the nose up and push the tail down, the opposite to planes nowadays.

Ailerons are a completely different matter. This will be reversed once again. If we want to bank RIGHT, we pull the aileron stick right. If we want to bank LEFT, we pull the aileron stick left. So let’s say we’re banking right. One wing goes up, one goes down. See if you can guess which one does which. It’s pretty simple, really. By the way, I’m talking as if we’re standing behind the plane, and looking down the fuselage to the nose.

The answer is: the right wing goes DOWN, the left wing goes UP. To do this, we want to have the flap on the left wing go DOWN (the opposite), and the flap on the right wing go UP (again, the opposite to the elevator). It’s exactly the same if we want to bank left; just the flaps are the other way around. A good way to remember this, which was mentioned on Flite Test, is: when you pull the stick right, the right flap comes up and gives the stick a High-5. When you pull it left, the left flap gives the stick a High-5. It’s that simple.

I hope you now roughly understand the basics of elevators and ailerons and how airfoils work, and why they are important. Oh, and for your information, this does not mean you NEED to use an airfoil on every plane. For example: the Nutball does not require an airfoil. Don’t get overly stressed on building a perfect airfoil for your first scratch build.