Athough this was my first frame to break 100 mph, the main goal for this frame design was just to throw something together that was easy to work on when things went wrong. When things went wrong with the V1/V2/V3 projects, it meant hours of work just to open and then close the frame back up. I based it off a design I made in the fall of 2015:
The idea here was obviously to limit the cross section in the horizontal plane. However, it only made sense if the motors were on an angle which I had set to 15 degrees.
I wasn’t going for speed here since the cross section of the frame (relative to the normal of the center of thrust) was basically an air brake. But at lower speeds, it was efficient. I am not sure how it compares to anything else out there, but on one flight it was able to cover 11.1km with a 3s 2700mah lipo. Although speed wasn’t the idea here, I still did a few speed runs now and then where it consistently hit around 135kmh (when taking into account any type of tailwind).
In an attempt to see if I could break my personal distance record of 11.1km, I tried a few ways of streamlining the frame with some thin plastic, and when that didn’t fit/work very well, streamlined it with electrical tape! I never got a chance to try for the distance record since I destroyed my 2700mah lipo. However, even though it was mostly streamlined for distance, it was enough to help it hit 163kmh or 101.3mph:
Limiting the cross section is important, but keeping it streamlined is also an important factor. The effect of not having a streamlined body is (of course) turbulence. Turbulent air creates chaotic pressure differences wherever it occurs and most quad designs have many, many places for this to occur. Since different areas of the frame are experiencing different amounts of turbulence at any given time, it will cause the quad to roll, pitch, and/or yaw. We don’t see this, however, since the flight controller is compensating for the turbulent forces acting upon the quad. We can see this happening when looking at blackbox data. On a turbulent frame, you will see more “flutter” in the motors which hurts speed since not all motors are at 100%.
This was my most memorable flight with this frame. I will be honest, I wanted to do a quick climb just below cloud level (clouds were about 700ft that day). I gunned the throttle to climb, but it didn’t respond when I reduced throttle:
All I could hear was the sound of the F1 fading away as I watched my FPV monitor in horror (picture reception was perfect). Luckily the motors stopped, free fell a few seconds, then failsafe kicked in ( I have it timed to last 10 seconds). The receiver regained connection and I was able to bring it back in. I was not paying any attention to the altitude in the OSD and I was not recording the FPV video either so I have no idea how high it got.
With the SK1 project on hold, I had a chance to revisit this frame and make a few refinements – actually, I HAD to due to another rx connection loss (I do not recommend the AR6200 rx!!!). See the video above to view the first time it happened.
Revisions that were made were very minor:
- Added serial DSMX Lemon rx (embarassing how long it took me to learn how to do this)
- Moved video tx to the rear
- Added streamlining “panels” from the FPV camera to the battery
The streamlining panels are made of thin Delrin material and cut into shape. Its a down and dirty way to quickly shave away air drag (this is a work in progress, will add photo when it is finished).