cartercg

The rudder and elevator are both more sensitive with the contra drive. I guess that the straighter airflow over the tail improves the efficiency of the fuze and the stab, which means that even at low throttle settings these surfaces are very efficient, and that translates into more control at lower throttle settings. There is perhaps also less speed dependency with right thrust (no longer required), so the plane holds heading better when rolling at lower airspeed. That said, the Peridot still flies better at higher speed so I will still fly it relatively fast. The advantage is when having to do downwind rolls (like the four roll combo in the F15, or the two rolls on 45 in the P15), as ground speed is high but airpseed is low, and the contra makes it easier to do axial rolls with the lower airspeed.

I agree with the feedback from Brenner....the airframe has a natural speed range within which it which it flies best. The contra can just broaden the speed envelope. A plane that likes to fly fast should still be flown fast with a contra. But I've only got a couple flights with the contra, and these are my first impressions.

Cons of the contra is having to find 160g saving to cater for the additional weight (as compared to my Pletti with extra light carbon spinner and prop). Having to move the battery tray back 5cm to retain the same CG. Having to grind the front of my OXAI plane off :-(

I find my present setup does not have the speed/acceleration I want, but I expect that will be addressed via props with more pitch.

Efficiency is very similar to a single prop setup flown at the same speed and distance. I probably used around 3200mAh for a P15 flown at a moderate pace in calm conditions. If guys with contras are using lots of mAh it has more to do with their flying style and not the drive itself. I'm using Hyperion 4600mAh packs, and don't expect a problem with capacity.

Regards
Clint