A few months ago I aske the RC/FPV community a series of questions what they use and how they fly. Today, it is time to announce the results!
In total, I got answers from 1739 people. I will not lie: the number is like 10 times higher I expected it to be. So that you! I appreciate the effort!
Let's go through the question one by one, with a short commentary.
Do you know this old saying “If you want something done right, do it yourself”? I do and sometimes I just live according to it. Not always, I’m not crazy, but at least from time to time!
I fly 7-inch FPV drones a lot. To be honest, they are my favorite flying devices. There are a few good 7-inch frames, like TBS Source One for example. There is a difference between good and great tho. I do think that Source One is a good frame, there are a lot of things on it that do not make me very happy tho! The list might not be very long, but it is relevant:
props in the view
limited space to install split-like hybrid cameras
I love 7-inch FPV drones and during the last year, they were my most used FPV gear. For freestyle, cinematic, cruising and long-range. I currently own 3 7-inch FPV drones and 4th one in the assembly process. I think of myself as a 7-inch expert. I’ve wasted enough money and equipment to know what works and what does not work well with 7-inch propellers.
This year my friends and I stared a local FPV drone racing series. Nothing serious, just a couple of guys meeting once in a while and measuring times over the track. 100% amateur thing. After the second race, I’ve realized that I do not have a drone designed for racing: more than 400g without a battery! That is just too heavy for any competitive racing. The solution was simple: I need a good racing machine. Frame designed with racing in mind. Much lighter, simpler, and more agile than the current one. Preferably Stretch X design.
As a result, Race Day Quads Mach 1 was born
Race Day Quads Mach 1 is a straightforward frame. Four arms, bottom plate, top plate, four standoffs, and 3D printed camera mount. It turns out it’s all you need for racing. Everything above that is just a dead weight that serves no purpose during the race.
Comparing to my previous racer, Mach 1 was lighter by almost 150g. Almost a third lighter! And I could feel the extra swiftness and agileness while flying. Race Day Quads Mach 1 helped me to get the second place at the end of that racing season.
I have a theory that 7-inch FPV quadcopters fly “below expectations” due to frame resonance, I did not expect, so many pilots agree with it. We had nice talks in comments, I’ve learned a lot about stiffness and moment of inertia (that you Pierre-Louis). Many of you shared some of their tricks and ideas on how to solve that. Let’s start testing some ideas how to fix that!
I will keep it short: drones are not designed for a long flight. Sure, you can put bigger props, bigger batteries and make it lighter, but comparing to even simplest airplanes, there is nothing to compare.
The conclusion is: try airplanes. They are cheap, simple, easy to fly with modern flight controllers and are much more efficient than drones!
Do you know, that with proper equipment you can fly your drone at night? In darkness? Without any lights? You only need a special camera that can see in the dark. I’m using RunCam Night Eagle that unfortunately is now discontinued and only Night Eagle 2 is available.
So, you got yourself a 7-inch quadcopter drone, you try to tune it, and you finally discovered that something is bloody wrong? Whatever you do, no matter how long you tune the PID gains and filtering, you can not get rid of jello and some strange vibrations? Welcome to the club mate!
Apparently, scaling 5-inch frames to 7-inch ones in XY axes does not work! Longer arms equal lower modal frequencies. Bigger propellers equal lower vibration frequency. After combining both factors, we have frame oscillations that are happening on the hardware level. No way you can tune that thing out. To make thing worse, 2205 and 2206 (even 2207) motors does not have enough torque to quickly change 7-inch propeller rotation speed.
What are Motor Stop and Airmode features in INAV and how they differ from each other when used on multirotors and fixed-wing airplnes? Should you use Motor Stop on multirotor? Should you use Airmode on a fixed wing? Long story short:
On multirotors, Motor Stop not recommended to use while Airmode is recommended to use. More than that, you can not use them both at the same time, since they exclude each other!
On fixed wing aircrafts Motor Stop and Airmode are highly advised to use together.
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