Recent advances in Unmanned Aerial Vehicles (UAVs) have enabled a myriad of new applications in many different domains from personal entertainment to process and infrastructure online monitoring in large industrial sites, among other. Our work focuses on how one can use several small UAVs collaboratively to provide extended reach to an online video monitoring system. We demonstrate how a TDMA overlay using 802.11 radios on low-cost commercial-off-the-shelf (COTS) UAVs can be used to enable high channel utilization in multi-hop networks, by avoiding mutual interference. This paper presents an extensive network characterisation and modelling of the quality of the UAV-to-UAV link, in terms of packet delivery ratio as a function of distance, packet size and orientation. We show that this platform is non-omnidirectional in the flight plane and that UAV-to-UAV communication ceases around 75m. Then, we solve the mathematical problem of finding the optimal link length and number of hops that maximize the end-to-end throughput, as we extend the network. We validate our mathematical model with extensive experimental campaigns transmitting payloads up to 200m (over 802.11g @ 54MBps).