Updated: Feb 10, 2019
There are many factors that contribute to the performance of a paper airplane, but there is one thing almost every new designer gets wrong: the placement of the plane’s center of gravity. That is right. If you learn this one principal for correctly placing the center of gravity on your paper airplanes, it will DRAMATICALLY improve their performance. As usual, I discuss the topic at length in the video, but I'll summarize it below.
I know many of you don't know what the center of gravity is, so I'll go ahead and define it for you. I do suggest you watch the video from about 45 seconds in to a minute and 40 seconds, as the visuals provided there will help you to understand the concept. But, basically, the center of gravity is the balancing point for an object. Here's a tougher (and more thorough) definition from google:
Center of Gravity:
a point from which the weight of a body or system may be considered to act. In uniform gravity it is the same as the center of mass.
Seriously, watch the video. It'll help!
Once you understand what the center of gravity is, it’s time to ask the question: Why is it important? The placement of a plane's CG can determine whether it is capable of generating and maintaining forward momentum. If the center of gravity is way too far back (aft) on the plane, it will fly more like a falling leaf than a paper airplane. If it is a little too far back, it will climb and stall before diving and crashing.
I located the center of gravity on a number of my successful paper airplane designs and calculated the percentage of the planes' wing areas in front of, and behind their CGs. I found that there was a lot of consistency from plane to plane.
Emperion One had 25% of its wing area in front of the center of gravity. That means that there is a higher concentration of layers at the front of the plane than at the back of the plane (making each square inch at the front heavier than a square inch at the back of the plane). Swallow had 27% of its wing area in front of the CG.
Plasma Z — 25%.
Invictus — 25%
Circuit Racer — 24%
Onslaught — 25%
Stratus — 25%
Marauder — 23%
Zoomerang — 26%
The consistency is astounding. Of the planes I checked, I had only one outlier — Arrowhead, which has only 19% of its area in front of its CG.
After this, I was curious about other people’s designs, so I tested two of the best in the world: Sky King, the world record holder for time aloft, and Suzanne, the world record holder for distance. Guess what I found: Suzanne had 23% of its wing area in front of its CG and Sky King had 25% of its wing area in front of the CG. They fit the narrative quite well.
Now, don’t let all of these numbers intimidate you. You don’t have to do this kind of testing to correctly place your plane’s center of gravity. It’s actually a really intuitive process.
If your plane has a tendency to climb upward and stall, its center of gravity is too far back. If it has a tendency to dive, the center of gravity is too far forward. Keep in mind that planes will fly differently at different speeds. So a plane that dives when thrown gently may fly quite well with a harder throw. A plane that glides nicely with a soft throw may climb and stall with a harder throw. So, to some degree, the proper balance of a plane also depends on how you would like for it to be thrown.
So, let’s say that when you throw your paper airplane, it climbs and stalls, or it struggles to generate any forward momentum at all. You know that the center of gravity it too far back on the plane, but you’re not sure how to go about fixing it. There are a couple ways to go about this.
The first is to simply fold some layers forward, and you’ll move the Center of Gravity forward with them. Another easy way to move the CG forward is to fold the nose of the plane down. I know it seems a little counter-intuitive to move layers backwards, but reducing the wing area in front of the CG is another way to effectively move it forward. As long as you don’t fold the nose too far down, you should be good to go. One more way to move the center go gravity forward is to fold the top edge of your paper down before you begin folding the plane.
If you find that your plane dives and you need to move CG backwards. Just fold fewer layers forward than you currently have in your design. Problem solved!
And with that, I’ve taught you all you need to know in order to properly place the center of gravity on your paper airplanes. Go create some amazing designs!