Building a 10" long range FPV drone
A year ago I built an ultra light 5" long range drone (read about it here) which in the end didn’t quite meet my expectations. My main conclusion was that size really matters when building long range quads and this winter I will be working on a 10" drone.
Note: This is a work in progress post. I will update it with more information and photos when the components arrive, during the build and after the maiden flight.
After a quick initial research at similar drones I decided on a couple of design choices:
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I would use 8S power train. While 6S is frequently used on 10" drones, the motors required for 10" drone would pull a lot of amps at 6S voltage and thus would require an expensive ESC. I will go in more detail when I look at ESC options, but there’s a big cost increase when you need to upgrade to a 80A capable ESC.
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It should be in X8 configuration. This will be an expensive build and crashing after a component failure could be costly, not to mention the damage such a big and heavy drone can do if it drops. In X8 configuration 2 motors work in parallel in each corner and provide redundancy for a single motor/prop/ESC failure. It will also allow me to use smaller motors (since we have twice as many) and further reduce requirements for the ESC.
I will go through all of the components I considered and explain how I made my choices.
Components
Frames
There are a lot of frame options for 10" drones. I considered frames from AOS RC, iFlight, HGLRC, GEPRC and Foxeer. The biggest problem when you enlarge a typical quad frame to take 10" props is resonance performance. The arms get so long that any micro bending happening at the arms gets amplified to a degree where the flight performance suffers. I have rejected Pulsar LR10 frame because it didn’t have any feature to reduce the impact of this. I also didn’t like the price tag (and the weight) on iFlight Helion 10. Out of all of the options I considered, I thought AOS UL10 had the best chance to perform well. Vertical truss design has a proven record in large professional cinelifters. The only downside I see is more complicated maintenance but on 10" long range drone you are not going to be replacing arms very often.
| AOS UL10 V5 | iFlight Helion 10 | HGLRC Rekon10 | GEPRC Pulsar LR10 | Foxeer Aura 10" | |
|---|---|---|---|---|---|
| Weight | 380g | 540g | 396.7g | 576.3g | 390g |
| Arm support | Vertical Truss | Double Arms | Reinforcement Bar | No | Reinforcement Bar |
| Camera Cage | Aluminum | Aluminum | Carbon Fiber | Carbon Fiber | Carbon Fiber |
| Plate thickness | 2.5mm | 4mm | 3mm | 3mm | N/A |
| Arm thickness | 3.5mm | 8mm | 8mm | 7mm | N/A |
| Price | $150CncDrones | $300AliExpress | $110GetFPVAliExpress | $140GetFPVAliExpress | $150GetFPVAliExpress |
Motors
The motors typically used on 10" drones are 3110-3220 in size. I think the larger 3220 size motors would be a good choice if you go with a more typical 4 motor configuration. However, even on 8S they would require a beefy 80A ESC. I found 4 motor options suitable for 8S build (650-750kV). Primarily due to good price and availability I decided to go with GEPRC EM3215. They look like a great fit based on the specs, I will test them out and share the results.
| BrotherHobby Tornado T5 | GEPRC EM3215 | BrotherHobby V4 32.5-15 | BrotherHobby Avenger | |
|---|---|---|---|---|
| Stator | 31 x 15 | 32 x 15 | 32.5 x 15 | 32 x 20 |
| Stator Volume | 11319mm³ | 12061mm³ | 12443mm³ | 16082mm³ |
| kV | 640 | 750 | 665 | 700 |
| Peak Current^1 | N/A | N/A | 53A | 73A |
| Weight | 116g | 122g | 121g | 140g |
| Shaft | 5mm | 5mm | 5mm | 5mm |
| Mounting | 19x19 | 19x19 | 19x19 | 19x19 |
| Price | $45BrotherHobby | $32GEPRC | $35BrotherHobby | $53BrotherHobby |
1: Measured at 8S with HQ 10x5x3 prop
ESCs
While there are 8in1 80A ESCs designed specifically for a drone like this I don’t think they are the best choice. They are very expensive and a single ESC failure would require replacing the whole thing again. I think the best choice would be to go with single ESCs like Foxeer Reaper 80A. However, I am trying to keep the budget down so I will go with 2x 4in1 65A Foxeer Reaper ESCs. They feature a burst current rating of 100A, have a good track record for reliability and are reasonably priced.
| DYS AM32 4in1 | Foxeer Reaper 65A | Foxeer Reaper 80A | iFlight Thunder | |
|---|---|---|---|---|
| ESCs | 4 | 4 | 1 | 8 |
| Input Voltage | 2-8S | 3-8S | 4-8S | 4-8S |
| Current | 65A | 65A | 80A | 80A |
| Burst Current | 80A | 100A | 145A | 100A |
| Firmware | AM32 | BLHeli32 | BLHeli32 | BLHeli32 |
| MCU | F4 | F4 | F4 | G0 |
| Price | $50GetFPVAliExpress | $85FoxeerAliExpress | $60GetFPVAliExpress | $400AliExpress |
Flight controllers
There are not that many 8S compatible flight controllers. Technically, you don’t need the flight controller to be 8S compatible because you could power it off a regulator. However, I think it’s better to keep things simple and go with one of the 8S capable options. I found 3 very good options: Matek H7A3-SLIM, Foxeer H7 and BrainFPV Radix 2 HD. All of them are 8S and 8 motor capable, have powerful H7 processor, barometer, black box and plenty of UART ports. They all also have a common weakness: all of their 9-10V regulators are only 2A capable and I would prefer more for power hungry digital VTXs. You may see some other features like CAN port or specific gyro chip that may drive you one way or the other. I didn’t have any specific needs there so I decided to pick the more cost effective Matek H7A3 option.
| Matek H7A3-SLIM | Foxeer H7 | BrainFPV Radix 2 HD | |
|---|---|---|---|
| Input Voltage | 8S | 8S | 8S |
| Motor outputs | 8 | 8 | 8 |
| MCU | H7A3 | H743 | H750 |
| IMU | ICM42688P | MPU6000 | BMI270 |
| Baro | SPL06 | DPS310 | DPS310 |
| BEC | 5V/2A + 9V/2A | 5V/2A + 10V/2A | 5V/1.5 A + 9V/2A |
| UART | 6 | 6 | 6 |
| CAN | Yes | No | Yes |
| Analog OSD | Yes | Yes | No* |
| VTX Switch | Yes | No | No |
| Black Box | 128MB | 16MB | MicroSD |
| Price | $65GetFPVAliExpress | $105FoxeerAliExpress | $113GetFPV |
Other components
The other components will not be any different from other FPV drones and will depend mostly on your preferences.
I chose Walksnail Avatar GT kit for video transmission because I prefer high definition quality but I think you could get better range for less money with analog system.
I had a spare BetaFPV SuperD ELRS Diversity Receiver which I used in the past and I know it will take my far. I may eventually upgrade to new generation dual band (2.4G and 900MHz) ELRS receiver for more range and reliability. You could also use Crossfire or Dragon Link if you prefer those.
I used Caddx Walksnail WS-M181 for GPS but any u-blox M10 based GPS will be just as good. It also has a built in magnetometer which can improve autonomous flight modes.
For batteries, I picked up a single CNHL Racing Series 5200mAh 8S Li-Po battery. I plan to use it for testing and maiden trip but I will eventually build 8S2P and 8S3P Li-Ion packs out of high energy density 21700 cells. You could purchase such battery packs but they are pricey ($369 - $604).
When it comes to chargers, I never had a problem with ToolkitRC. They are attractively priced and convenient to use. I noticed some bad reviews online and you may want to pay extra for a more reputable brand like HOTA or ISDT but I went with ToolkitRC M8P.
Final parts list
| Frame | AOS UL10 V5 |
| Motors | GEPRC EM3215 750kV x8 |
| ESC | Foxeer Reaper F4 65A BL32 x2 |
| Flight controller | Matek H7A3-SLIM |
| Receiver | BetaFPV SuperD ELRS Diversity Receiver |
| Video Transmitter | Caddx Walksnail Avatar GT |
| Camera | Caddx Walksnail Avatar HD Pro |
| Propellers | Gemfan 1050-3 |
| GPS | Caddx Walksnail WS-M181 |
| Buzzer | JHEMCU JHE42B-S |
| Battery | CNHL Racing Series 5200mAh 8S |
| Charger | ToolkitRC M8P |
I expect to receive all parts over January and build it over the next couple of months. Expect more information coming in February/March.