## Principles of aerodynamics

The forces and counter forces of flight

With Instructables you can share what you make with the world, and tap into an ever-growing community of creative experts.

How it Works »New Instructable »The forces and counter forces of flight

Next weekend, the 28th and 29th of May, this year's edition of the Maker Festival Twente will be held in En…

Hi Everyone! Sadly, Instructables will not have a booth at this year's Bay Area Maker Faire. BUT, some of…

Community Manager Instructables is looking for an awesome person to join our team of Community Managers! …

Hi! I recently had the chance to interview Kludge77. Not only does he have quite an extensive instructable…

Dear instructables family, I come to you today to ask for your loving support because the Positive "sunshi…

Hello! I recently had the joy of interviewing Tomatoskins. Not only is he an awesome maker, but he's also a…

It's cool to see where your ibles end up getting a mention. Here is a CBS Sacramento morning news talkshow…

Hi everyone, I’ve got a good one for you today! Our friends at Parabo Press are giving 1,000 people in the …

Hi, my name's Oli and I am a speech therapist - aka speech pathologist in US. I am looking for a way (e.g.…

For my, or should I say our next Instructable I want to do a little experiment. The goal is to make a colab…

FEATURED CHANNELS

Join 2 million + to receive instant DIY inspiration in your inbox.

active| newest | oldestSay you have an object falling through the atmosphere, if that object is falling less than gravity, it's producing some drag and/or lift. If the object is falling slower than terminal velocity then there *has* to be lift being produced.

Let's consider a free body diagram in the vertical direction for a glider: in the -Y direction you have gravity or the weight. In the positive Y direction you have a component of the drag and a component of the lift. Sum all of these and you get a force which is equal to m*a. In level flight a=0 so the forces sum. Now, the force of gravity is equal to m*g where g is the gravitational acceleration. If m*a is less than m*g then there has to be some positive upward force. This comes from a component of the drag and the lift.

As I posted earlier, a symetric airfoil at 0 degrees angle of attack (AoA) produces 0 lift, but at positive AoA it produces positive lift. If AoA is negative, it will produce negative lift, that is a force downward.

You might be confused about airfoils as they are conventionally drawn. The typical airfoil is drawn with a rounded top and flat bottom. This is known as a "cambered airfoil". Basically a cambered airfoil produces lift at 0 AoA (the trade off is that they often stall earlier), but there is a negative AoA where there is 0 lift produced, which we sometimes use to compare the lift-curve slope with other airfoils. (Lift-curve slope is the graph of lift vs. AoA, the slope of which is often 2*pi [don't ask me why]. To explain further, in aero we often use C_l; coefficient of lift. Now C_l=C_l_alpha*alpha where alpha is the AoA, so that C_l_alpha is the lift curve slope (this was for a symetric airfoil, for a cambered airfoil, there's a constant in there)). That was longer and probably more confusing than I intended, if you have a question, just ask.

I also forgot to mention that a flat plate *can* generate lift when it sees a positive AoA.

I mean this type: http://www.instructables.com/id/EV3GW00JZ4EYF8LZG3/ -- not the kind that you spin (for boundary layer effects).

Lets stop bickering and get to the point of this thread!exactlyaerospace stuff, but we still need to know it (well, some of it).Anyways, as long as I'm posting, in level flight Thrust=Drag and Lift=Weight.

I'm just confused as to what the point of it is.Me too :P