DF Mini Spirit

Introduction:

I came across DongHo Lee's video where he flies this thing with a 2s li-ion pack and 1306 motors. I was pretty amazed that he flew it with 3" props and such a small motor.

Components:

• DF Spirit mini wing

• Turnigy plush 12a 2-4s ESC

• SZ Speed 1407 4000kv motor

• 2x 5g servos

• Noxe F4 FC

• Happymodel Diamond VTX powered by a 5v regulator

• Generic micro camera

• Frsky rxsr receiver

• Beitian 180 220 GPS

Conclusion:

Dry weight came to 80g. DongHo's version was 69g. I definitely added a bit more reinforcement in mine such as a carbon spar and extra tape to make sure it can survive some crashes until I get it tuned. He shared with me that the CG was 80mm from the nose, which saved me a lot of work indeed. It'll be interesting to see how it flies.

Update 4/3/21: Maiden didn't go well. Crashed quite a few times and broke the canopy before finally figuring out that the 80mm CG didn't work out. For me, the CG was much further back (100mm). Now I need to figure out how to rearrange the electronics to balance it out.

Update 4/9/21: I added extra vertical stabilizers since I was getting some weird behavior in the air, but I finally found a day where winds were only 5mph and discovered that the real issue was that the CG is now too far back. There was a lot of pitch sensitivity and the plane rolling out of control from time to time, so I'm going to need to move the CG up a bit again and add more reflex. Unfortunately, I lost a battery in the field again with all the wild oscillations during testing. This wing has been difficult to tune mainly because finding a day with less wind is so difficult. I am still perplexed as to why they didn't add any information for the CG.

Update 4/11/21: Swapped to a BN220 GPS for better reception. Also swapped to manually adjustable elevon links for easier CG changes. Weight is now 87grams.

Update 4/14/21: Finally got another day with less wind (5-8mph). Finally got the CG correct with a lot of reflex and it flew without any issues. I've finally settled on 90mm as my preferred CG. It requires a lot more reflex than I would've originally guessed. Cruises at around 30% throttle and the max speed on 2s is around 90kph. I would imagine that a lipo would yield much faster flight times than the 2s 18650 used during testing.

In summary, I would not recommend this as a good wing (at least for 18650s) since it doesn't really fly particularly well with the heavy wing loading. It requires a lot of reflex (limits inverted flying) which reduces the efficiency overall. It doesn't handle the wind well at all and while it is capable of performing most aerobatics, it just doesn't do them well with the heavy batteries. I suppose you can use it for mission/waypoints, but then it becomes very shaky with winds and will not yield any good images. However, if you were to build it light and nimble, it may very well prove to be a much better craft.

Update 4/18/21: Tested some winglets on there to see if it would fly better, but it doesn't really seem to matter, so I removed them again. Unfortunately, the camera is out of focus and I may need to take it apart to fix.

Efficiency Logs:

• 10km (823mah used) | 2s lion | 82.3mah/km

• 11.41km (908mah used) | 2s lion | 79.57mah/km

Update 5/31/21 - I am retiring this because this just isn't a good plane. I think I may rebuild it to be lighter instead.