Originally Posted by Rolf D.
why not 4 turbines
Haha There actually is a serious answer... up to 13lb of thrust there are only the Lambert Kolibri that performs(!) One will do 6.6lb of thrust with a system weight of just under 1lb. Two will do 13lb of thrust with a system weight of 1.8lb. 4 of them will do 26lb of thrust and weigh in at 3.9lb... but then you can as well choose any turbine doing 26lb of thrust that weighs the same and save 3*turbine costs