||I have been asked whether it is possible to fly bigger aircraft (bigger than 1.6 2 metre wingspan) with electrics, without having to spend a fortune.
The answer is yes, but as always with electrics, you have to get everything right. Good motor, switch, cable and cells are essential and good means powerful with little current loss, not necessarily expensive.
Paul Vidler of Kootingal flew a 2.5 metre wingspan QB 2500 glider powered by a Kyosho 360ST (improved ferrite motor) direct drive and 7/Sanyo N800 AR cells. A Taipan 7 x 4 prop, an STW 40 amp switch and Sermos connectors were used. The performance of this combination was satisfactory. I have even heard of aircraft up to 3 metres wingspan flying with this combination, but I do feel it is preferable to add a gearbox and a larger, folding propeller for aircraft so large. This would increase efficiency giving more torque for a lower battery power consumption.
One other strategy is to increase the number of cells to eight, or even ten. This will make the aircraft much more lively, but introduces charging problems. One has to purchase a charger with the capability of charging more than 7 cells from a 12 volt car battery (like the GWS MC2002).
Helmut Meyer of Bremen, West Germany, has a 2.5 metre electric glider design called the Albatross. This design is intended for a 600 motor with a gearbox added, and ten cells. This combination works very well. It is necessary to experiment with propellers to find the optimum size for this combination.
Let me encourage you to give it a go build a bigger glider, make it light and do not skimp on the electric flight set-up you put in to it, and you will be happy with the outcome.