Expert: Mark Janus - 2/12/2010

Question
Dear Mark Janus,
   Hi my name is Houston and I am 11 years old. I am doing my science fair project on paper airplanes.  I would be grateful if you would answer some questions that I have for you.  First, is it true that the wider the wing-span, the better it will glide?  How does a paper airplane fly?  Does gravity have something to do with it? Does bending the wings help the plane fly or does it make it worse?  Is it true that if you keep the nose sharp it flies better?  And finally, why do some planes go up and down a lot?  Thank you for your time.

                               Sincerely,
                                Houston

Answer
Hi Houston,

I apologize for the delay in getting to your question(s).  Yes the wider span reduces a form of drag (the force slowing the plane down) called induced drag thus allowing the plane to glide farther/longer...  Basically all airplanes fly by pushing down on the air to stay aloft.  Gliders use gravity (and altitude) as a source of energy to keep the airplane moving through the air.  Bending (arcing) the wings (downward) helps the wing push the air down more efficiently...  A sharp nose is not really necessary....  and gradual pointed tail is probably more important (due to drag issues)...  Some planes go up and down due to the forces acting on the airplane not being in equilibrium (balanced)...  Believe it or not, but a paper airplane has some interesting flow and dynamics associated with it.  I suggest you ask your mom or dad to got to amazon.com and look into getting a book on paper airplanes...  I know of a few that explain all of this pretty well.  Most are paperback books that are not very expensive.

Thank you for your question,
mj