How to Trim a Paper Airplane

Hi Folks,

Paper Airplane Design #61 - Delta Wing, Slow Flight

Paper Airplane Design #61 – Delta Wing, Slow Flight

I appreciate your interest in my paper airplane designs. When I developed them, I had two criteria that I followed:

  1. They had to have the highest performance possible. I spent hundreds of hours of wind tunnel development to attain the highest performance – on the average, they generate three times more lift over common paper airplane designs.
  2. They had to be easy to construct. My designs have little in common with the art of Origami, the Japanese art of paper folding. Instead, I focused on a series of easy to build designs, that fly like real full-sized aircraft. Instead of paper folding, I focused on aerodynamics.

I’d like to talk a bit about trimming a paper airplane for flight once it’s made.

Paper can be folded into many shapes and sizes, but it is an unstable material. It warps, unfolds and especially if it is subjected to humid or moist conditions, it will swell to some degree. These changes can result in reduced performance and constantly changing flight characteristics. So to obtain continued performance flight after flight, every airplane requires trimming periodically from time to time to fly properly. In fact, few, if any paper airplanes ever fly well on the first flight – they all require a few test flights to trim them to obtain optimum performance. For once these airplanes leave your hand – they must fly on their own without any pilot control input.

One common error that I’ve seen a lot of during the seminars that I conduct, is the importance of making each side of the airplane a “mirror image” of the other. Think about it; every full size airplane that you have a ever seen, or bird in flight – each wing and tail surface is an exact opposite of the other.

Having said all of this, the most critical part that you will make on your airplane is the matching the fold of your second wing, to the first. This will guarantee that both wings have the same amount of incidence. This will reduce any tendency of your airplane to turn or worse, corkscrew in flight. I cannot emphasize the importance of this second wing fold too highly.

 

folding a paper airplane wing

From The Paper Ace: Folding a paper airplane wing.

You should consistently make every effort to create each wing as a “mirror image” of each other during the construction phase of the paper airplane, to obtain the best performance. Taking an extra minute to ensure that each wing is the exact opposite than the other will eliminate a host of instability and trim issues that other folks go through.

When you have completed the airplane, take a look at it from the front. Hold the airplane at arm’s length and point the nose to you and sight along it’s length. Look at the amount of upward sweep, or dihedral of the wings – it should not be excessive, but you should have a slight amount. Use the photographs of my designs for reference. This is usually no more than 5 degrees – just enough to create a measure of lateral stability.

An airplane also requires static stability in the pitch (up-down) axis. Just how the airplane is trimmed in the pitch axis plays an important part in flight performance. When you trim an airplane, you are trimming it for a given flight speed. Once a properly designed airplane is trimmed, no matter how it is upset from what turbulence it encounters, it will always try to right itself and fly at that particular airspeed. This is a subject that I cover completely in all three of my books.

Once the airplane flies properly in pitch, the next step is to trim it properly in the yaw (or left-right) axis. In trimming out yaw, the first thing to look for is the leading edge slat folds on the wings. Make sure that the left wing and the right wing have the same amount of slat deployment. This can be seen by looking at the airplane with the nose pointing at you. Tilt the nose up and down, to view the leading edge of the wings to determine that they have the same amount of slat deployment. These aerodynamic devices are a standard feature of my designs.

Your first flight is a gentle one, you need to trim the airplane in pitch, not hurl it through the wall. Taking a few extra minutes to trim your airplane for proper flight will give you an airplane that will fly where you want it to go. You do this by gently holding the airplane and launching it from eye level with a slight nose down release. Your airplane weighs less than a ¼ of an ounce – it doesn’t require much airspeed. A good rule of thumb is that for the first flight to be about the speed of a person walking.

If the airplane noses down, bend the trim tabs on the rear of the airplane slightly up. I will take a few flights to obtain the proper amount.

Just how the airplane is trimmed in the pitch axis plays an important part in flight performance. When you trim an airplane, you are trimming it for a given flight speed. Once a properly designed airplane is trimmed, no matter how it is upset from what turbulence it encounters, it will always try to right itself and fly at that particular airspeed.

Once you achieve this, you will be able to make your airplane go where you want it to. I play a game with my cat, where he will try to knock down my airplane as I glide it past him. He will use the couch, coffee table or ricochet off the wall to get altitude to meet the airplane as it glides past. If you have ever seen the movie, “King Kong”, you will understand what I am talking about – at times, it looks very similar. With the predicable flight characteristics of my designs, I can get it past him most of the time. I usually have a few airplanes made in advance, so after he grabs and crushes one, we can still continue the game.

I’d be eager to hear from you via email about your flight experiences with these designs.