The utilization of unmanned aerial vehicles (UAVs) for chemical application has become a topic of great interest to both researchers and the market in recent times. Producers have proposed the use of drones for joint spraying as a means of enhancing precision agriculture and productivity. However, chemical spraying is a highly specialized field where the quality of the spray is critical so the used UAV have to be precise and reliable. Within this paper will be presented the process of developing a tricopter-hexarotor chassis type UAV, electrically driven, fitted with a 66 litres tank and 6 anti-drift nozzles which will be used for precision spraying of agricultural crops based on preprogrammed flying missions.