Nowadays, the research in unmanned aerial vehicles has experimented a large increase, since the technology that compose this kind of aircrafts has been developed in order to achieve many kinds of tasks in several fields. In this paper, it is presented the design criteria of a Quadrotor Unmanned Aerial Vehicle with an uncommon small size and heavy payload carrying combination requirement. It will be performed a selection of the appropriate mechanical structure and its configuration. This study will focus in the structural components selection that will allow fulfilling the requirements of the project such as the energy consumption, the autonomy of the vehicle and the stable flight. The result will be a remote control and automatic aircraft with the appropriate size for both outdoors and indoors tasks.