UWL is now called "Igniter Class" and it is part of Underground Drone League. View the new website for updated information.

BUILDING AN UNDERGROUND WHOOP

There are multiple ways to get a UWL legal build . Some of those options may be buying and modifying a BNF, buying parts for a new build, using spare parts you have laying around, or converting a 65mm racer. No matter what you plan on doing, consider this page your ultimate resource for getting an Underground Whoop League spec drone built.

Last Updated: February 4th, 2024

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Building with a BNF

There are currently no complete BNF's that meet the UWL spec. However, there are several BNF's that can be easily modified to meet the spec. Here is a list of BNF's and their required modifications.

BetaFPV Meteor75 1s (2022)

Modifications

  • Add weight

  • Add LEDs

  • Change Motors

Pros

  • Comes with BT2 connector

  • Good Analog Camera

  • Cheapest and most complete BNF build

Cons

  • Frame only fits select batteries and can be awkward with some flight controllers

Modifications

Pros

Cons

Buy

  • Add weight

  • Add LEDs

  • Change Motors

  • Comes with BT2 connector

  • Good Analog Camera

  • Frame only fits select batteries and can be awkward with some flight controllers

Happymodel Mobula 7 1s

Modifications

  • Add weight

  • Add LEDs

  • Change motors

  • Add BT2 (recommended)

  • Swap camera (recommended)

Pros

  • 12a ESC

  • Cheap

Cons

  • FC doesn't fit other frames due to camera plug

  • Poor camera

  • Poor integrated VTX

  • PH2 battery lead

Modifications

Pros

Cons

Buy

  • Add weight

  • Add LEDs

  • Change motors

  • Add BT2 (recommended)

  • Swap camera (recommended)

  • 12a ESC

  • Cheap

  • FC doesn't fit other frames due to camera plug

  • Poor camera

  • Poor integrated VTX

  • PH2 battery lead

Happymodel Mobula 6 HDZero

Modifications

  • Swap frame

  • Swap propellers

  • Extend motor wires (or replace motors)

  • Add LEDs

  • May need slightly more weight added

  • Add BT2 (recommended)

Pros

  • High quality HDZero video

  • Comes close to weight without trying too hard

  • Required frame swap means using any approved frame you want

  • Extended motor wires can be a new color for extra flair

Cons

  • Expensive

  • Extensive modding (requires soldering)

  • PH2 battery lead

Modifications

Pros

Cons

Buy

  • Swap frame

  • Swap propellers

  • Extend motor wires (or replace motors)

  • Add LEDs

  • May need slightly more weight added

  • Add BT2 (recommended)

  • High quality HDZero video

  • Comes close to weight without trying too hard

  • Required frame swap means using any approved frame you want

  • Extended motor wires can be a new color for extra flair

  • Expensive

  • Extensive modding (requires soldering)

  • PH2 battery lead

Happymodel Moblite7 HDZero

Modifications

  • Swap motors

  • Add LEDs

  • May need slightly more weight added

  • Add BT2 (recommended)

Pros

  • High quality HDZero video

  • Comes close to weight without trying too hard

Cons

  • More expensive than Mobula 6 HDZero conversion

  • Needs motors swapped (requires soldering)

  • PH2 battery lead

Modifications

Pros

Cons

Buy

  • Swap motors

  • Add LEDs

  • May need slightly more weight added

  • Add BT2 (recommended)

  • High quality HDZero video

  • Comes close to weight without trying too hard

  • More expensive than Mobula 6 HDZero conversion

  • Needs motors swapped (requires soldering)

  • PH2 battery lead

BUILDING FROM SCRATCH

One of the main benefits of UWL is that you can use all kinds of different parts and still have a competitive build. Don't feel like you need to use only parts on this list to be competitive. In fact, the spec was designed so that most parts could be scrapped together from your bench. So don't be afraid to use those old 802 motors you haven't touched in years.

Frames

Use any frame from the approved frame list and you'll meet spec. These are just our favorites!

Meteor75

Pros:

  • Durable

  • Many colors

  • Somewhat light (Capable of meeting minimum weight with HDZero if other parts are carefully selected)

Cons:

  • Small battery tray only fits certain batteries

  • Can be quirky to use with some flight controllers. The best paired flight controllers seem to be the BetaFPV ELRS, Happymodel Cross, and iFlight Blitz

Buy:

Mobula 7 V4

Pros:

  • Fits X12 FC

  • Ducts are high enough to protect a double stacked HDZero VTX

  • Battery tray fits all batteries

Cons:

  • Might not be as durable

  • Battery tray is loose on some batteries (I use E6000 to thicken the tray and make it tighter)

  • Not as many color options

Buy:

Fractal 75

Pros:

  • Easily replaceable ducts

  • Use any duct you want

  • Multiple duct colors on one build

  • Carbon fiber base

Cons:

  • Expensive

  • Trickier to build

  • A little heavier

Buy:

Motors

You must use motors from the approved motor list. Here are our thoughts on some of them!

UWL Lite 802 19,000kv

Pros:

  • Durable

  • Unibell

  • Wire PCB

  • Super lightweight; pairs perfectly with HDZero builds

  • Long motor wires for 75mm

  • Directly support UWL!

Buy:

Tiny Whoop 802 Hex

Pros:

  • Durable

  • Unibell

  • Wire PCB

  • Super lightweight; pairs perfectly with HDZero builds

Buy:

Happymodel EX 0802

Pros:

  • Durable

  • Unibell

  • Wire PCB

  • Super lightweight; pairs perfectly with HDZero builds

  • You might already have it on hand!

Cons:

  • In some circumstances, you may have to replace or extend the motor wires to fit your frame

Buy:

Tiny Whoop UWL Limited Edition

Pros:

  • Durable

  • Unibell

  • Wire PCB

  • 1.5mm shaft for those who want the extra durability

Cons:

  • Heavier than other motors such as the UWL Lite

  • Tests ever so slightly slower than the UWL Lite

  • No longer available. This is a collectors item now! If you have it, you might want to leave it on the shelf

Tiny Whoop 802 Boost Juice

Pros:

  • Durable

  • Unibell

  • Wire PCB

Cons:

  • Heavier than other motors such as the UWL Lite

  • Tests ever so slightly slower than the UWL Lite

Buy:

Flight Controller

There's not a single flight controller on the market that I can give a glowing recommendation to. The most important thing in a flight controller for me, however, is having an external VTX. I believe this really helps improve the reliability and repairability over time, as well as providing the clean video for you and others. That being said, here's my reluctant recommendations on a flight controller for a UWL build.

BetaFPV F4 1s SPI D8/PNP

Pros:

  • BMI Gyro

  • Extra Pads to Add an External ELRS RX

  • Cheap

  • Blackbox

  • Comes with BT2 battery lead

Cons:

  • ELRS not built in. ELRS RX must be added separately

  • D8/Redpine is the built in protocol, neither of which are recommended for UWL

Buy:

BetaFPV F4 1s ELRS V2

Pros:

  • BMI Gyro

  • ELRS on a UART (I personally would consider this to be a con but most would not)

  • Cheap

  • Blackbox

  • Comes with BT2 battery lead

Cons:

  • Only one 5v and GND pad. This means you'll either need to share pads between your cam/vtx or you will need a VTX with 5v and GND pads.

  • ELRS Receiver known to break.

  • Much more difficult to add an external receiver to than the D8/PNP version

Buy:

Happymodel Superbee F4 Lite ELRS

Pros:

  • Lightweight; pairs well with HDZero

  • Comes with long screws and grommets for pairing with HDZero

  • Preconfigured for HDZero

  • Cheap

Cons:

  • Usually has ICM Gyro which is known to eventually start having problems

  • SPI Receiver (I personally would consider this to be a pro but most would not).

  • Comes with PH2 battery lead

  • Discontinuted

Buy:

Happymodel Cross F4 ELRS

Pros:

  • BMI Gyro

  • ELRS on a UART (I personally would consider this to be a con but most would not)

  • Easier to add external receiver to than BetaFPV

Cons:

  • ELRS receiver is known to go out and may require and external one to be added

  • Discontinued

Buy:

Analog Camera

When it comes to analog video systems, you'll have to make up a couple grams to get up to weight compared to an HDZero build. For this reason, I typically recommend bigger and heavier cameras. This not only helps you get up to the required weight but gets you a better image to fly with. It's one of the main ways you can add weight to your build that's actually meaningful and helpful.

BetaFPV C03

Pros:

  • Good Image

  • Available

  • Cheap

Cons:

  • Lightweight, might have to add extra weight to your build

Buy:

Foxeer Predator V5 Nano

Pros:

  • Top level analog video quality used by most 5" racers

Cons:

  • Expensive

  • May or may not limit options for the rest of the build due to weight

Buy:

Foxeer Pico Razer

Pros:

  • Good Image in all environments

Cons:

  • Might be a little light for some builds

  • Discontinued

Buy:

Caddx Baby Ratel 2

Pros:

  • Good Image

  • Heavier weight

Cons:

  • Might have weird video under black lights

  • Might go black and white in dark environments, which provides a clearer image but might not be desirable

Buy:

Receiver

There are plenty of great receivers out there. Use what you like, but we do recommend using an external one! They tend to be way more reliable and higher performance than their internal counterparts

BetaFPV ELRS Lite Flat Antenna

Pros:

  • Great Performance

  • 0.5g

  • Lowest profile RX out there, easy to fit on a build

  • Super durable and reliable

  • Cheap

  • No need for extra external antenna

Cons:

  • Some people find ELRS difficult to learn

Buy:

TBS Crossfire Nano RX

Pros:

  • Crossfire is very popular and you may already have it on hand

  • 1g+ the antenna makes it good for getting up to weight if your build needs it

  • Some people find Crossfire easier to use than ELRS

Cons:

  • More expensive than ELRS

  • Requires an external antenna

  • Crossfire isn't as fast as ELRS

  • The extra weight might make it a little trickier to get HDZero down to the minimum weight

  • Larger size might be a little trickier to fit on a build

Buy:

ImmersionRC Ghost Zepto RX

Pros:

  • 0.4g + External Antenna

  • Can control Tramp VTX's without the need for Smart Audio. Your build needs 1 UART only!

  • Some people find Ghost easier to use than ELRS

  • similar speed to ELRS

Cons:

  • More expensive than ELRS

  • Requires an external antenna

  • Hard to find stock

Buy:

Analog Video Transmitter

There are plenty of great video transmitters out there. Use whichever one you like. This is just my favorite.

Happymodel OVX300

Pros:

  • Great video

  • Somewhat cheap

Cons:

  • No 5v/GND pads for camera.

  • Hard to find

  • Has had a significant price increase

Buy:

LEDs

Tiny Whoop has a whole collection of LEDs that are great for UWL builds. I'm just gonna put my favorite here, but if you want to see the whole collection, this is where you can find it: https://www.tinywhoop.com/collections/leds

COB Strips

Info:

  • Can use as little or as much as you want to get desired weight

  • Just solder to VBAT and GND

  • Glues to frame

  • Durable

Cons:

  • Requires a little extra soldering to hook up your own wires

Buy:

4-LED HARNESS - 1206 LEDS

Info:

  • 0.4-0.5g depending on how you install

  • Just solder to VBAT and GND

  • Glues to frame

  • Durable

  • Short version available as well

Cons:

  • Not as cool as Cobs

Buy: