1. Executive Summary
April moved Project Spearhead from analytical foundation into structural design, hardware procurement, and a parallel prototype build. The fuselage truss and engine bay were sized, a full transition flight analysis was completed against ArduPilot’s three-phase state machine, and an ArduPilot QuadPlane reference guide was released for Spearhead’s configuration. The Stork quadplane was selected as a learning testbed and most of its components were ordered. VTOL powertrain selection was finalized for the main aircraft. The wing spar layout pivoted from round to square carbon tubes at the end of the month and is being redesigned around that change.
2. Project Progress
Team Formation
| Member | Experience Level | Team | Weekly Commitment (hrs) | Areas of Expertise / Championed |
|---|---|---|---|---|
| alperenag | Level 5 | Core | 32 | Project Lead |
| Zeynep | Level 4 | Core | 20 | Flight Mechanics |
| Erick | Level 4 | Core | 5 | Electrical Layout & Avionics |
Progress Overview
April was the structural design month. The fuselage and engine bay were sized, and a transition analysis closed the last open question on the flight envelope. The Stork quadplane was selected as a testbed and all parts were ordered. Late in the month the wing spar and boom layout pivoted from round to square carbon tubes after a deeper structural review, and is being redesigned. The first analytical tools from March were merged into the GitHub repository.
3. Major Studies
Fuselage Structural Design
The fuselage frame was sized as a 540 mm carbon tube truss with four longerons, two plywood wing spar connection bulkheads, and two aluminum bulkheads at the ends.
Fuselage Skin and Engine Bay
The fuselage skin uses ASA-Aero panels on the top surfaces (engine bay and electronics access) and Oratex film elsewhere to save weight and print time. The engine bay is lined with aluminum HVAC tape as a radiant heat shield. A 90° exhaust elbow routes the muffler downward and clears the cylinder fins for cooling airflow. Cooling balance was checked at cruise (~2 kW heat input vs ~1.6 kW airflow dissipation) and judged marginal but acceptable for the prototype.
Transition Flight Analysis
A coupled VTOL/pusher transition model was built around ArduPilot’s three-phase SLT_Transition state machine (AIRSPEED_WAIT, TIMER, DONE). The model captures the parasitic drag from VTOL thrust pitched at Q_TRAN_PIT_MAX = 3°. At 18 m/s the wing already carries 80% of the weight, so the 5-second VTOL ramp-down has adequate margin and confirms ArduPilot’s default strategy works for this configuration.
ArduPilot QuadPlane Reference
A reference guide was released by filtering the official ArduPilot Plane documentation down to a Quad-X pusher IC configuration at 25 kg MTOW. Tailsitter, tilt-rotor, and other non-applicable sections were removed. The document covers frame setup, motor ordering, transition tuning, weather vaning, assistance modes, and SITL setup.
VTOL Powertrain Selection
VTOL motor and ESC selection was finalized after comparing T-Motor and Mad Motor options. Mad Motor 150 KV with the AMPX 80A DroneCAN ESC was selected on the basis of weight, efficiency, DroneCAN support, and documentation. Six motors were ordered, four required plus two spares. Fixed 26x7.8 propellers were chosen over folding props because of locking and cruise-airflow concerns. Lightweight carbon props remain a future weight-reduction option (~80 g savings across four).
Stork Quadplane Testbed
The Stork (Flightory) was selected as a learning quadplane to build pilot proficiency before the main aircraft. A bill of materials was prepared, mapping the manual’s recommended parts to Turkish vendor equivalents. All parts were ordered. The battery selection moved from 4S Li-Po to 6S after review. The 3D-printed airframe build started during April with LW-PLA and ASA-Aero on the skin parts and PETG-CF on the high-load mounts.
4. Goals for Next Month
- Complete the Stork airframe build and run first hover and forward flights.
- Build and test the Spearhead test wing V2 with laser-cut balsa ribs.
- Finalize the square-tube spar and boom layout, including the wing detachment mechanism.
- Run the Here4 CAN-to-PWM bench trial.
- Begin assembly of the main fuselage truss frame.
- Generate the aerodynamic database for the flight simulation model.
- Define the electrical layout, including harness sizing and the tail-side CAN-to-PWM architecture.
- Set up the flight mechanics simulation environment, including ArduPilot SITL with Spearhead dimensions.
5. Budget & Resource Allocation
Project Expenses
Reimbursements totaling $1,981.84 were submitted this month, covering test wing materials, Stork procurement (electronics, carbon, filament, battery, FC, props), Spearhead transition test items, labelling and tooling, and AI coding assistance. The breakdown can be found here.
Team Members Compensation
The project team was compensated for $16,000.00 this month. The breakdown can be found here.
Total
The total expense of Project Spearhead in April is $17,981.84.