Check out the whole "T" copter family: I've been experimenting to find a strong "tubular" profile that could be printed reliably. The angled sections in these designs are 35 degrees to vertical - so well within the typical 45 degree capability of most printers. They arms only present about 11mm of flat surface to minimize obstruction to airflow. The rest of the design are a collection of ideas that have accumulated over the past year building various quadcopters and Y6 configurations (3D printed, aluminium and bought frames). 17 July 2014 No version number change but a couple of tweaked files: 14 Feb 2014 16 Feb 2014 I printed all parts with 40% infill, 2 shells and 3 top/bottom layers. Feel free to experiment. I didn't play around too much with the settings as these gave me a good strong result. A quick word about scaling According to Wikipedia apparently "there is no scale information [in STL files], and the units are arbitrary". There is often confusion with STL files and metric versus imperial (inches) units. I designed these parts in Sketchup using metric units and they import correctly into my slicer (which is also set to metric). If you have issues, check your application to see if has a way to select metric or alternatively scale down by a factor of 25.4.