Velomobile on a recumbent trike
 

Hello, i'm new here, i'm from Italy (so sorry for bad english :)); i'm planning to build by myself a recumbent trike with an aerodynamic body. I plan to use it everyday to go to work to make some kilometers of street.
But sorry i'm a little bit ignorant about aerodynamics and by search on internet i can't find what kind of shape is the most aerodynamic to go fast, to cut the air, to go fast straight.

Here my question what is the best shape to cut the air for a velomobile trike?

Here i make some existing samples to understand what is it a velomobile trike:

http://www.velomobil.no/

Thank you all in advance, if you need more information just ask.

a long teardrop is what you are after (eg a bit like some of the vehicles at your link) - see this wiki:

http://en.wikipedia.org/wiki/Drag_coefficient