Project Hymenoptera is a conversion of the Lynxmotion Mini Hunter V-tail frame into an octocopter from its standard quadcopter configuration.
Project Stats:
]Frame Lynx Motion Hunter V-tail Mini x2 Custom mod /:m]
]8X Emax MT1806-2280Kv Motors (4x Cw, 4xCCw)/:m]
]8x Lynxmotion 12A/18A ESCs/:m]
]4x HQ 6x3 Prop(2CW/2CCW)/:m]
]2x HQ 6x3 Prop(CW/CCW custom cut to fit under front arms)/:m]
]2x HX 5x4x3 (CW/CCW custom cut for tail top motors)/:m]
]Afro32 Full Flight Controller with BaseFlight /:m]
Final Acro (manual) Hover Stability before advanced tuning:
Final Acro (manual) flying around before advanced tuning:
Partial Build Log on Imgur with build photos: imgur.com/a/LWIIc
Flight Video is in, it is worth a watch 
Comparable to a go-kart with Nitrous
Very well done and really happy it flew!
A few questions out of curiosity:
- Any impressions on having a three bladed prop above a two-blade?
- Did you find the overall payload capacity increased?
- Overall impressions on going from a quad to an octo? Just aesthetic or practical?
I have taken this to the next level and am now working cutom motor mixes as a true X8 (previously it flew on co-rotating instead of counter rotating props due to the difference of induced yaw (typical) and thrust yaw (vtail special) actually counteracting in the typical mode. But other then the yaw issue I have seen improvements already.
Answering your questions:
-
Three bladed props do better capturing and accelerating the air coming form the top motor. On the front arms so far the best configuration has been with two blades on top slightly larger than three blades on bottom with slightly more pitch. I have a full test rig, but it went down before this project started and I decided the try and see method. I actually have an order of props coming in to get some real numbers. On the back the inside V motors necessitated much smaller prop diameter, I had concerns from the onset that these would be useless. I was wrong. By using three bladed props (and I have 4.0 pitch currently with 4.5 on the way) and cutting them down I have as much surface area as possible. They produce enough lift to be of use in flight. More than anything flying FPV you can stall the two vtail outer (traditional) props and still have enough lift to get back to flying. I choose to use the larger 2 blades on the outside here for the additional thrust. Three blade props are much better balanced inherently. But have a reduced efficiency. Every prop has its use, but I’ll be honest I have never used tri-blades for a gain except on this project.
-
Absolutely, almost detrimentally. Flight times are not the best, but you can easily fly 5000mah or more on this setup. When flying with the lighter batteries the performance is not much different but flight time is minimal. I do throw a 60C 1200mAH on occasion and its insane with lack of weight. But its hard to get more than 4 minutes of aggressive flying out of that. But what a four minutes! Overall payload 800+grams not bad for its size. And plenty of power to weight. As a rule when using coaxial setup with N motors it acts as a flat setup with N-2 motors. (Aka a octo X acts like a flat 6) add to that the V-tail and undersized props and things get interesting. Hence the custom motor mixing. But all in the power is fantastic, its just not always where you expect it right now.
-
The transition was a “because I cant find anyone else” type of choice. Aesthetically it was just mean to look cool (a stupid requirement but that was it). And to see if its been done. The outcome has been much more pleasing. Flight times are not what I would want. But to be honest the motors I used are overpowered as it is. I think this build would have had a better outcome leveraging the additional thrust and using lighter motors, working the electronics to be a little more efficient for its size. One of the coolest features beyond retarded control and speed is the redundancy. V-tails have props sticking out wide at the front and odd angles at the back. It is not hard to clip something trying FPV in any 250, let alone a V-tail. Due to the redundant motors and power of this octo it is very hard to knock out of the sky. Any two motors can be stalled and as long as they are not the same arm flight pretty much resumes as normal. Not saying it can take a branch full on, but it can take a brushes here or there very well. Would I recommend the general person go to a coaxial octo, no. If you have some specific desire redundancy, extra power, but decreased flight times, or whatever else it could benifit your with though, it is a good way to go.
