So, I've started experimenting with ultralight 4 inch builds about 2 years ago. Each time those were extremally nice machines with two, major, flaws Short flight time and a huge LiPo sag. Fortunatelly those problems trouble me no more! Say hello to my newst ultralight 4inch low kv 6s racer!

Firstly, as it's the most important factor for the 4 inch build - weight. I think that in this case it is execptionally good - 150g without lipo and 254g with 6s 550mah lipo.

What made this build possible are the motors. And what can I say? Those are the highest quality motors I have ever seen. Hobbywing Xrotor Race Pro 1408 2400kv. Compared to the Brotherhobby 1507 those have a much stronger magnets (N54) which are packed much closer together. Also the gap between stator laminations and magnets is much smaller than in the case of Brotherhobby 1507. The motor is extremally notchy.

Amp draw is quite low, the maximum number I was able to achive during flight is 52A for the whole drivetrain. That is why I am able to use xt30 connector without melting it. The lipos also does not sag and I got avarge of 3:30 minutes of flight time on the race track (compared to about 2 minutes of flight time in case of 4s 550mah and BH1507 3600kv).

The frame is a prototype frame given to me by my sponsor DemonRC, which I am very thankful about and is called DemonRC legit 4x lite.

The rest of the parameters:
TWR circa 15,27:1
Disc Load 5.07.