1. The problem statement, all variables and given/known data For a Science Olympiad project I need to make a rubber motored helicopter, and with this I need to find the best design for one. One special rule in this is that Chinook styled helicopters get 3x their original flight time, I was wondering if that would be just to encourage students to do that type of helicopter, or if they are just harder to make. Also i have been looking for formulas about the efficiency of helicopter rotors with no success. Most models I have seen were Chinook helicopters and they were made from Balsa wood. Any help with some equations to help me out with lift or drag would be helpful. 2. Relevant equations N/A 3. The attempt at a solution I have tried researching equations, and have also asked my teacher and she left me with more questions than answers because she wants me to figure it out. Luckily this is due May 28th so I have awhile and I was spending hours on typical helicopter designs with no avail.