I just recently flew a 130cm Atom 80 E-prop on the SP140 and figured I’d share that experience in case anyone else was curious. My hope was that the less aggressive pitch might reduce torque and that I’d be able to even further reduce the max power from chill mode, which still produces way more power than I need. I’m also not a huge fan of the SP140 frame and figured that if the 130 prop was viable, I could work on moving the SP140 power system over to my Miniplane, which is a frame I like much better but cannot accommodate a 140 cm prop.
Bottom line: not viable due to the end-of-flight power drop.
In preparation, I installed the prop and decided I needed to be able to get ~11.9 kW max power to be in the same ballpark as the Atom 80’s advertised 16 hp to even attempt launching. My ground runup showed 11.5 kW in Sport mode which I figured was close enough. I also reversed the prop direction in the ESC configurator and swapped the Iris weight shift offsets to the other side. Launch was MUCH longer than I was used to. I obviously had much less power than on the stock SP140 prop, and compared to my Miniplane this machine was about 30 lb heavier while also producing less power. Climb was noticeably less than my Atom 80, measured at approximately 250 fpm vs 350-ish fpm on a similar configuration with the 80cc engine. Cruise power was in the low-4 kW, which is similar to power consumption with SP140 prop on this glider (24m Spyder, 150 lb pilot). I think endurance would’ve only been a few minutes less, maybe 10-15%. Noise was not much worse at cruise but had a noticeably higher tone and louder sound at full power compared to the 140 prop achieving a similar climb rate. Low maneuvering was a dream, which is what I was most hoping for because I still find maneuvering the 140 to be awkward when playing around down low with constant power changes. With the Atom prop: negligible torque and able to comfortably use the entire throttle range even though I would’ve liked maybe a little more power as I was still sub-80cc output. The real killer though was the late-flight climb performance. At 83.8 off-power volts, full throttle power had dwindled to 7.7 kW — enough for a slow climb, but not nearly enough for a safe margin for low maneuvering. I am well aware of the power drop off with the stock 140 prop, but even at the end of flight I have more than enough power for practice launches and landings even in Chill mode. I suppose I was just unsure whether that would still occur using such an underpropped configuration. Turns out it very much did. Overall, I think an interesting experiment even if not a viable option. If I was really committed to finding a viable 130cm prop I could try an EOS prop or something more aggressively pitched but with the same bolt pattern, but at this point I figure I’ll just keep flying the 140 and get used to the torque and power. I still really like the idea of a big, slow prop from a noise standpoint, but I’m still growing into it and it’s just a lot more torquey and awkward on the ground than I expected.
