Project Šemík - 1.5m FPV Glider

SHEMIK FC FULL CARBON – F5K Thermal Model FPV Conversion

Description

Project Šemík is a custom high-endurance, full-carbon F5K thermal glider modified for long-range FPV and stabilized flight. By pairing lightweight, high-precision glider servos with an active flight controller stack and an efficient 4S power setup, this airframe is tuned to catch thermals effortlessly while maintaining tight, locked-in control.

Wing-Mounted Battery Configuration

To preserve internal fuselage space for electronics and achieve ideal center of gravity (CG) balancing without adding dead weight, the battery is top-mounted directly on the main wing:

3M Dual Lock Attachment: Secured using high-tack 3M Dual Lock reclosable fastener directly along the wing root centerline, providing significantly higher shear strength and rigid locking compared to standard hook-and-loop tape.

Streamlined Mass Distribution: Mounting the pack over the wing root keeps the heavy mass aligned with the center of lift, preventing pitch instability and keeping fuselage air drag to a minimum.

Structural Modifications & Boom Reinforcement

Stock 3D printed PLA carbon firewall was replaced with a modified aluminum firewall.

To handle the additional torque of the power system and the dynamic forces of the wing-mounted battery, the carbon tail boom was systematically reinforced:

Tail-Boom: Thick heat activated glue shrink wrap extending through the primary stress-concentration zone near the fuselage junction to eliminate flex under load.

Applied a PLA print tow wrap bolted and bonded with thin epoxy around the boom mounting joints and tail-assembly anchor points to prevent delamination during hard landings.

Vibration Isolation: Dampened the internal electronics by using 3M Dual Lock under the all-in-one tray to protect sensitive sensors and avoid high-frequency mechanical noise reaching the gyro. Easily removable for maintainence.

All-in-one tray

The all-in-one tray for Šemík is a custom PLA 3D-print that acts as a unified "engine block" for all your electronics. By mounting the Matek FC, ESC, Crossfire Nano, GPS, and Nebula Pro camera onto a single modular pod before sliding it into the narrow fuselage, it achieves extreme high-density packaging while keeping internal wire runs neat and short.

https://www.thingiverse.com/thing:7387531

Component Notes

Airframe: SHEMIK FC Full Carbon F5K category thermal glider airframe

Battery: Tattu 4S 1050mAh/850mAh-HV Top wing-mounted via 3M Dual Lock for precision CG tuning

Flight Controller: Matek H743-WLITE Dual gyro, dedicated ArduPilot/INAV wing FC

ESC: Flycolor 80A ESC High-capacity ESC with ample headroom for burst amps

Motor: iFlight BOB57 2506 (1500KV) High-efficiency outrunner for light prop setups

Propeller: Gemfan 7042-2 (Clear) 7" bi-blade optimized for low-amp cruising efficiency

Aileron Servos: KST X06H (x2) Ultra-thin wing-mount digital micro servos

Tail Servos: KST X08 (x2) High-torque micro servos driving rear elevator & rudder

FPV: Caddx Nebula Pro System Digital HD low-latency FPV feed

Receiver: TBS Crossfire Nano RX Long-range control link

GPS: Matek M10 High-precision GNSS module for position hold / return-to-home

Build Notes & Tuning

AUW: under 600 grams

Battery Mount & CG: Top-mounting the 4S Tattu 1050mAh with Dual Lock makes CG adjustments fast and precise. The interlocking polyolefin stems lock the pack solidly into place, resisting lateral forces during high-G thermal banking or windy launches.

Power & Efficiency: The 4S pack paired with the iFlight 2506 1500KV motor and Gemfan 7042-2 bi-blade prop delivers strong climb authority while keeping thermal floatation light and agile.

Control Surfaces: KST X06H servos handle the thin-profile ailerons inside the wings with zero slop, while higher-torque KST X08 servos drive the rear elevator and rudder for sharp, immediate feedback.

FC Integration: The Matek H743-WLITE is mounted centrally inside the fuselage chamber with soft-damping tape to maximize gyro performance and keep wiring runs clean. Even though the AUW is a more than what its desgined for, its extra power and reinforcements make up for it--it has a large wing area and it's more than enough to glide with.

The build was an engineering project to fit common FPV electronics components in a tight space where a small 2s battery would sit.

Flight-times vary, you can fly it until you get bored. 14 to 18 minutes of continuous powered cruise and 30-40 minutes of thermal soaring on a single charge in light-to-moderate wind conditions.