I have been doing research over the last week or so into how you could build a UAV that could replicate what can be done by MQ-1s (Reapers) and other high-cost military vehicles. One thing that seems to be concurrent across most medium ~ large platform UAVs is that they all use engines.
The thing is I have never seen a UAV on here that uses an engine. Now I know that this is because platforms used by 90%+ of the community are foamies but what if you were to use say a platform like the Hugin or the UAV 3000 which can accommodate these sorts of engines.
So my question to the community is why aren't gas engines used by us today? One reason I would look to use an engine is because I would love to have flight times >4 hours. I don't know if this is possible but if you were to use a single cylinder engine that you get from HobbyKing for <$200 could you get it to run for a while?
I ask this as I would love to be able to create a platform that could fly for long duration flights that would fly along the coastline, over the sea, that has an APM and gimballed zoom camera that could fly for miles providing telemetry via a 3G link.
If anyone knows the performance and fuel efficiency of these sorts of engines it would help greatly.