# Airplane design

1. Jul 3, 2006

### aerodynamickid

Hi. I'm a middle school student messing around with some paper airplanes. I am wondering how the size of the paper I use affects the properties of flight like distance and flying time and how well the plane flies. I tried a few sizes of paper and found a good one. What controls this? I know you can't make a plane arbitrarily small or large, but what is the physics involved?

Thanks!

2. Jul 3, 2006

### RainmanAero

Hello AeroDynKid:
What do you mean by "size of paper"? Do you mean only the thickness, or do you also mean the length and width? For any given length/width a greater thickness of the paper will provide a higher structural rigidity for your airplane design, but it will also increase the weight, and one thing about airplanes is you learn to keep weight to an absolute minimum!

Wing Aspect Ratio (AR) is something you should learn about if you have not already investigated it. The low relative airspeeds of a hand-thrown glider generally call for a higher aspect ratio for the wing planform. This is where stiffer/thicker paper can make for a better wing.

Static pitch stability margin (the distance between the airplane's center of gravity and the aerodynamic Lift/Drag center) is also important to understand. Make sure the airplane center of gravity is forward of the aerodynamic force center caused by the wing. This is why some people will fold a paper airplane and then attach a paper clip to its nose... this moves the center of gravity forward.

Rainman

3. Jul 3, 2006

### Hawknc

Now this is my kind of aerospace engineering. I think RainmanAero covered pretty much everything you'd ever need to know about making paper aircraft...just remember that the two most important forces acting on it are lift and weight. Obviously to keep it in the air you want to maximise lift while minimising weight. High AR, maybe a bit of angle of attack on the wings if you want to get complicated, and flaps at the back can all increase lift. A larger wing area certainly helps as well, but that increases weight so you need to be careful.

4. Aug 23, 2008

### JonnyV70

Does the paper clip trick actually work? I thought it would just cause the plane to nose dive most of the time? I guess most of the designs I use are already weighted to the front.

Last edited by a moderator: Jan 6, 2012
5. Aug 24, 2008

6. Jan 5, 2012

### gpwilson

Why does moving the weight forward help so much? Is it due to the fact that the weight would try and keep the tip down, causing Newton's 3rd to put more pressure back on the plane?

7. Jan 6, 2012

8. Jan 7, 2012

### bigfooted

How large a paper airplane do you want it to be? I remember my faculty built a paper airplane with a wingspan of 14 meters. They were in the Guiness book of records with it. Don't know if they still are. Here is a picture (it flew so well that it hit the other side of the hall and the nose got deformed):

http://www.anp-archief.nl/page/55731/nl