How to Build a 3-Inch Cinewhoop FPV Drone: Parts List & Step-by-Step Guide

A cinewhoop is a small FPV drone with propeller guards, built for smooth, slow filming indoors and close to people and objects. The 3-inch size is one of the most popular, with the widest choice of frames and parts. This guide builds one around a DJI O3 air unit on 4S power, with an analog alternative, and keeps the weight just under 250 g.

3-inch cinewhoop parts list

The table lists every part the build needs, what to check before you buy, and matching products. The example build uses DJI O3 digital video, which the frame's camera cradle is designed for; swap the video rows for the analog option to cut cost.

Tools you need

• Temperature-controlled soldering iron with a fine chisel tip, 63/37 rosin-core solder and flux; the pads on a 25.5 mm board are small.
• Digital multimeter and a smoke stopper (a current-limiting fuse for the first power-up).
• Hex drivers (1.5 and 2.0 mm), side cutters, wire strippers and tweezers.
• Heat shrink, zip ties, double-sided foam tape and blue thread locker.
• A computer with Betaflight Configurator and the ExpressLRS Configurator, and a small fan to cool the air unit on the bench.

Step-by-step assembly

1. Check that the parts fit together

On paper, confirm that the frame and AIO board both use 25.5 × 25.5 mm holes, the motors match the frame's 9 × 9 mm pattern, the propeller hub fits the motor shaft (1.5 mm T-mount for the 1404 motors above), the battery plug matches the frame's XT30, and every part is rated for 4S.

2. Decide the camera and the weight budget

Choose the payload before you build. Staying under 250 g makes the drone easier to fly legally in many countries, and it only works with a light build: the O3 records 4K on board, so no extra camera is needed, and the 660 mAh pack is the largest that keeps the example build under the limit. A full-size action camera pushes a 3-inch past 250 g and needs the 1505 motors and 5-blade props from the parts list.

3. Build the frame and mount the motors

Assemble the frame with its supplied hardware and check that every guard is round and clears its propeller. Mount the motors with M2 screws short enough to clear the stator windings, with a drop of blue thread locker on metal screws.

4. Mount the AIO board and solder the motors

Fit the AIO board on its supplied damping rings, arrow forward, and solder the twelve motor wires to their pads; wire order does not matter, as direction is set in software. Check the joints with a magnifier, since a solder bridge on a small board is easy to miss.

5. Solder the battery lead and capacitor, then test

Solder the XT30 lead to the battery pads, red to positive, and the supplied 35 V 220 µF capacitor across the same pads, observing polarity. Heat-shrink the capacitor legs and tuck it away from the propellers. Check with a multimeter that there is no short between the XT30 pins or from either pin to the frame, then make the first battery connection through a smoke stopper.

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6. Fit the receiver

Solder the receiver to a free UART, TX to RX and RX to TX, plus 5 V and ground. The receiver and radio must run the same major ExpressLRS version, so check before binding. Keep the receiver and antenna inside the frame, away from the propellers and carbon.

7. Install the video system and finish

Connect the O3 to the F722 board's DJI connector (or solder it to the F411's pads) and check the pinout against both manuals. The O3 needs 7.4–26.4 V, so it must run from battery voltage, never the 5 V pad. Seat the camera in the frame's cradle without letting the cable pull on it; a tight cable passes vibration straight into the footage. For analog, power the VTX and camera from the 5 V pad (the Zeus Nano draws up to 400 mA at 350 mW) and connect the VTX's IRC Tramp wire to a spare UART TX pad. Fit the antenna, canopy and strap, and leave the propellers off until setup is done.

Betaflight setup and first tests

Flash the AIO board's firmware target (GEPRC_F722_AIO for the F722 board above); the O3 needs Betaflight 4.3.0 or later. Then work through these settings:

• Ports: enable Serial RX on the receiver's UART; select MSP + DisplayPort for the O3, or IRC Tramp for analog.
• Receiver: choose Serial (via UART) and CRSF, bind, and check every stick and switch.
• ESC firmware: the 35A ESCs on both AIO boards run BLHeli_S, which sends no RPM data as shipped. Flash Bluejay with the online ESC Configurator to get bidirectional DShot, RPM filtering and Dynamic Idle.
• Motors: DShot600 with bidirectional DShot on, and motor poles set to 12 for the 9N12P 1404 motors above (14 for the 12N14P SPEEDX2 1505). A wrong pole count points the RPM filter at the wrong frequencies.
• Dynamic Idle: Betaflight's guidance is that ducted cine quads usually do better with higher idle values.
• Camera and flight mode: tilt the camera about 10–20 degrees. Acro mode usually gives the smoothest footage; in Angle mode, lower the angle strength to about 20 so self-levelling does not fight your inputs.
• Failsafe and OSD: put ARM on a switch, confirm with props off that disabling the radio's transmitter module stops the motors, and show battery voltage, a timer and link quality.

For the first flight, check that each propeller spins freely inside its guard, hover low for thirty seconds and land. A motor much hotter than the rest points to a bent shaft, a rubbing guard or a damaged propeller.

Getting smooth footage

• Fix the hardware first: a cracked propeller, a guard touching a blade or a camera cable pulling on the cradle all cause shake that no filter setting removes.
• Descend with some forward speed rather than dropping straight into the propellers' own wash, and practise each route in open space before flying it close to people or objects.
• Bullnose and five-blade propellers make more thrust for the same diameter, which helps a heavy cinewhoop, at the cost of efficiency and noise. Treat claims that a guard design improves performance with caution: guards add weight and drag, and good designs only keep the penalty small.

Calculations: weight and flight time

The example build uses figures from the product pages linked in the parts list.

• Frame 67.6 g, four EMAX E3 1404 3700KV motors at 9.9 g (39.6 g), AIO board 8.8 g, DJI O3 air unit with camera 36.4 g plus 3 g antenna, receiver 0.4 g, four T3x3x3 propellers at 1.48 g (5.9 g), and an allowance of 15 g for wires, XT30 lead, capacitor, screws and strap.
• Dry weight: about 177 g. With the 64.1 g GEPRC 4S 660mAh LiHV, all-up weight is about 241 g. With the 72 g 720 mAh pack it is about 249 g, and with the 79 g 750 mAh pack about 256 g, over the limit. Weigh the finished drone: an extra few grams of wire or a heavier strap can push it past 250 g.
• Current headroom: the E3 1404 3700KV peaks at 14.2 A on 4S, so four motors pull about 57 A at full throttle, well inside the 35A rating of each ESC. The 660 mAh 90C pack is rated for 0.66 × 90 = 59 A.
• Battery energy = nominal voltage × capacity in Ah: 15.2 V × 0.66 Ah = 10.0 Wh.
• Flight time (minutes) = capacity (Ah) × usable fraction ÷ average current (A) × 60. Using 80% of 0.66 Ah: at a 5 A average while cruising slowly, 0.528 ÷ 5 × 60 ≈ 6.3 minutes; at 7 A, about 4.5 minutes. For comparison, GEPRC rates its own CineLog30 V2, built on the same frame with 1404 motors and a 4S 660–720 mAh LiHV, at 6 to 8.5 minutes of low-speed cruising.

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Battery safety and flying rules

• LiHV cells are full at 4.35 V; standard LiPo cells at 4.20 V. Charge LiHV packs in LiHV mode and LiPo packs in LiPo mode, never the other way round. GEPRC's 660 mAh LiHV should not go below 3.5 V per cell and is stored at 3.80–3.85 V per cell. Charge on a balance charger, in a fire-resistant bag, and never leave charging batteries unattended.
• In the US, recreational pilots must pass the free TRUST test and register drones of 250 g or more. Flying for a business, such as filming a property for a client, falls under Part 107 instead of the recreational rules.
• In the EU, a privately built drone under 250 g flies in the A1 subcategory: it may fly over uninvolved people, though this should be avoided, but never over assemblies of people, and the operator must register because the drone carries a camera. A drone assembled from a kit sold as a single ready-to-assemble set does not count as privately built.
• Propeller guards make a cinewhoop safer around people, not safe: keep a clear distance and never fly over a crowd.