Inverted Motor mounted quad more stable?

[rellik28]

Hi everyone.. I'm planning to build a small quad for myself. Have zero experience on RC flight. In fact very very limited knowledge with regards to RC. But have always been fascinated with RC only no chance to get into it. So I have been reading up about quad coptors and came across this site and statement.

"The motors are on the bottom under the arms.
1.) More aerodynamically efficient with no prop wash interference and very little intake interference.
2.) Noticeably increased flight times, greater lift capability and quieter as well."

May I know what are your thoughts and views with regards to the above statement and
1.) Better stability? which relates to easier to control?
2.) I'm a bit confused. I thought the lift generated is due to the low pressure on the upper surface of the wing(propeller), so for this design, wouldn't the rotor legs and motors cause more interference? Or is it more negligible when compared to the air generated thrust?
3.) In other words? which is more sensitive? Generated lift? or Generated Thrust? although both are almost the same meaning?

Muahaha i'm getting real confused. Bottom line... what do you guys think of the above design? If it's better why are conventional multi rotors mounted above arms?

Thanks for reading.
Cheers

[purple]

At this point of your learning period, it is better to do what most of the multirotor flyers normally setup. If there is a lot of advantage in putting the propeller in the reverse direction (i.e. pusher setup), most of the multis that you will see are in reverse.

As a person having no RC flight experience, I would advice you try the normal setup first (propeller on top). This would give you more room for error in case the quad tip off..

[PaulDT]

^+1. Don't overanalyze things, unless your enjoyment in the hobby is nitpicking the technical details. Otherwise, the KISS rule applies.

But yes, there is a tiny bit advantage of the props underneath due to the absence of prop wash, but if this is significant enough in the hobby-level scheme of things, I don't know. Maybe it'll gain you a few seconds of flight time vs. with the props on top, with everything else being equal.

Stability with quads or multirotors has a lot to do more with the flight controller's ability keep the multi's intended attitude, which then relates to how well you did your job in tuning it. Other factors related to stability are motor-to-motor distance (larger is generally more stable), speed controller response times (faster is better), motor rpm (faster is better), properly balanced propellers, and correct CG.

[TomcatFLYER]

My humble input is:

as long as the z-cg is below the prop planes. it should be statically stable (Static Balancing Assuming all props output same thrust ).... dynamic stability (balance by correcting propeller thrust) depends on the FCC's capability and the PID settings.