this quadcopter has already gone through multiple design iterations. three of these made it into actual flying machines.

the design plans for the first can be found here:
http://www.thingiverse.com/thing:113703.

the design plans for the second can be found here:
http://www.thingiverse.com/thing:167001.

the third is not yet on thingiverse.

the following pictures show the various design iterations:

the following videos are the results of a few flights: