How Do Paper Airplanes Fly
So you’re wondering, how do paper airplanes fly? Before we dig into the discussion I’d like to recommend that you visit our page on the History of Paper Airplanes, because in it you’ll learn about the groundwork that led to the paper airplanes we know today. Suffice it to say, these pioneers weren’t searching for ways to make flying pieces of paper, they wanted to fly! In our quest to find out what makes a paper airplane fly, let’s quickly review some history.
Two British guys (Butler and Edwards) applied for a patent in 1867 for a “fueled” delta winged flying apparatus that looks remarkably similar to the paper planes we make today. But even before that, in 1799, another British inventor named Sir George Cayley became the first to apply the principles of aerodynamics as we understand them today, and he identified the four aerodynamic forces of flight: weight, lift, drag, and thrust. His work was crucial in developments leading up to man’s first flight, and indeed paper airplanes make use of these same principles today and must be looked at when answering the question of how do paper airplanes fly.
The elements of flight work hand in hand. For example, modern fighter jets are only capable of flight at higher speeds because they aren’t designed to maximize lift the way a glider is, but rather they’re designed to handle high speeds and for maneuverability and maximize thrust. A modern jet would plummet to the earth at slower speeds, whereas a glider would float effortlessly because it is taking advantage of lift, not thrust. A great book for anyone wanting to learn more about paper airplanes (also a GREAT gift for any child you want to inspire), The Great International Paper Airplane Book is full of information on the rich history of paper airplanes and many, many world-class designs you can make.
What Makes A Paper Airplane Fly
There is some degree of similarity between paper airplanes and real planes, but a significant difference is the way real planes are designed to actually manipulate wind to produce lift, countering some of the negative effects their weight has on flight. You can see how this lift works in the image here by TeachEngineering.org. As the wind strikes the wing it is divided, with some air passing beneath the wing and the rest floating across the top. Due to the shape of the wing the distance across the top of the wing is greater (from front tip to rear tip) than it is on the bottom, which forces the wind on top to move across the wing much faster.
We know from Bernoulli’s Principles that air speed and density will affect pressure, and so the faster moving air on the top creates a much lower pressure than is found on the bottom of the wing, and this is the beauty and genius of the wing design we use today. Because things always seek to move from an area of high pressure to an area of low pressure, this wing design actually causes the wing (the plane) to rise, which is the loft people refer to.
Obviously our paper planes don’t have wing shapes like this, but it’s important never the less to understand this basic principle of flight. If you were to create such a wing shape on your paper plane you could expect significantly longer flight time.
In this image you can see the four basic principles that affect flight, Lift, Thrust, Drag and Gravity. What makes a paper airplane fly? How do these directly affect paper plane flight? As you’ve likely guessed, most of our paper airplanes fail to make efficient use of lift when compared to our real plane counterparts, simply because we can’t replicate that wing design. But there are other principles of flight in which paper airplanes excel. Specifically drag and gravity.
Because of their light weight, paper airplanes are able to avoid most of the effects of gravity during flight… they’re just so light in relationship to their size and speed. Next, because of the way our planes are designed there isn’t much in the way of drag effecting flight (or hampering it). If you look at a paper airplane from the front or rear it will roughly resemble a large T; it has a small body. So because paper airplanes can minimize the effects of gravity and don’t have much drag to deal with, they’re able to utilize the thrust we give them quite well; flying both fast and far.
We should also talk about stability in paper airplane designs; its important and will affect the flight of every paper airplane design and will help you when you’re building your own. In this paper at UC Berkley Electrical Engineering and Computer Sciences department, titled “The Science of Paper Airplanes“, they write about stability in flight- “The simple answer is weight forward is good. In every object there is a center of gravity – a neutral point where all of the mass is balanced. If an airplane has a center of gravity ahead of the neutral point, then this plane is stable. If this center of gravity is behind the neutral point then it becomes unstable causing nose-dives and spins.” So planes like the Dart, which have a forward center of gravity, stability in flight is great. Wider planes like the Condor (a Glider), while more evenly balanced, tend to not have the same degree of stability. People tend to think that because darts are thin and narrow up front that the center of gravity is further back than it is. But remember all of those small folds you made when creating the plane? Those are all bunched up in the front of the plane giving it more forward weight.
But what about Gliders, paper planes which seem to float effortlessly across the room? First consider their design; most Gliders also have a lot of folded up paper in the nose, giving them a fairly decent amount of stability per our previous discussion. Now, take an umbrella and open it up, then drop it from a certain height. It drops relatively slow to the ground. Now close the umbrella and drop it from the same height. While it weighs the exact same, in a closed position it simply avoids the effects of drag and drops quickly. Large Gliders, with their greater wing surface area, also take advantage of this drag and together with lift give them a greater capability of longer flight. Be sure to check out the awesome site at NASA which talks about the flight characteristics and physics of paper airplanes.
So how do paper airplanes fly? Hopefully you now have a greater understanding of paper plane flight and also have some good leads on more information on what makes a paper airplane fly.
Which of the four forces of flight do you think are most important in paper airplane?