Here's one quadcopter design which is more efficient that most of older designs: http://www.geek.com/science/weve-been-designing-quadcopters-incorrectly-since-d

Here's one quadcopter design which is more efficient that most of older designs: http://www.geek.com/science/weve-been-designing-quadcopters-incorrectly-since-day-one-1577256/ http://www.geek.com/science/weve-been-designing-quadcopters-...