How does the length of the wingspan of a rubber engine airplane affect the airborne time of the rubber engine airplane?
There is a component of the total drag of an aircraft called induced drag that depends inversely on the aspect ratio. The length of the wingspan is a key element in calculating aspect ratio. Aspect ratio is defined as the square of the wingspan divided by the wing area. The higher the aspect ratio of the wing, the less induced drag it creates and a slightly higher lift is generated than a shorter aspect ratio wing. In other words, long narrow wings fly easier than short stubby wings, and they stay aloft longer, all other elements being equal. That's one reason commercial jetliners (and the albatross) have such long wings compared to jet fighters (and hawks). That's also how the wingspan of the theoretical rubber engine airplane affects the airborne time of the plane. For an article on aspect ratio from NASA, and a neat little JAVA toy that lets you play with wing parameters, click the link below.