Project Caribou - April 2026 Progress Report

General
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Project Caribou — April 2026 Progress Report

1. Executive Summary

April 2026 was Project Caribou’s kickoff month. The project moved from DAO/forum concept into an active engineering project with a GitHub repository, initial documentation, team structure, and multiple parallel workstreams covering mechanical integration, battery mounting and avionics/electronics.

The initial repository setup established Caribou as an open-source heavy-lift hexacopter targeting roughly 200 kg MTOW and approximately 100 kg payload capacity, with an 18S power architecture and ArduPilot-based flight stack. Early technical work focused on Phase 1 readiness: organizing the Fusion 360 workspace, uploading the current CAD model, creating PT1 documentation structure, defining the electronics project layout, and starting design work for the Caribou Battery Connector PCB (CBC_PCB) and Caribou Main PCB (CMAIN_PCB).

The strongest progress areas during April were:

  • Project organization: GitHub repository structure, PT1 documentation, Fusion 360 collaboration workflow, and self-contained KiCad project folders were created.
  • Mechanical/battery integration: The battery mounting bracket design was closed as complete for the initial design step. Follow-up work was opened to remove old brackets and prepare the frame for the new battery layout.
  • Electronics architecture: CBC_PCB and CMAIN_PCB development were scoped. The CBC_PCB received expanded documentation covering power architecture, connector pinout, requirements, and concept renderings.
  • Battery connector investigation: The team researched the correct connector interface for Tattu 4.0 18S smart batteries. A vertical connector was ordered, and follow-up tasks were opened for the 3D model plus KiCad symbol/footprint.
  • Telemetry and Caribou Hub: Initial issues were created for Caribou Hub V1 and a companion-computer telemetry handling system, including MAVLink, ESC CAN, BMS CAN, logging, and local network distribution.

The project is now past basic setup and entering the first real design-integration phase. May work should prioritize finishing the CBC_PCB and CMAIN_PCB development, sourcing the parts for the battery mounting design, preparing the airframe for the new battery layout, and narrowing the telemetry/sensor architecture into testable implementations.

2. Project Progress

Team Formation

Name Team Level Hours/Week Discipline
Alex Core 3 15 Avionics, Research, Caribou Hub
Dow Fisher KBM Core 3 20 CAD, PCB
Erick Core 4 5 Project Support, Research, Electronics
Julius Core 5 30 Project Lead

Progress Overview

Fusion 360 and CAD Collaboration

The team created a Fusion 360 project structure and collaboration workflow for Caribou. The workflow defines contributor sandboxes, a master assembly folder, part/sub-assembly organization, naming conventions, and rules to prevent unstable assembly modeling practices.

The current Caribou CAD model was uploaded to Fusion 360.

Relevant work:

  • Issue #4 — Fusion 360 project structure and workflow — closed
  • Issue #5 — Upload current Caribou model to Fusion 360 — closed
  • PR #11 — Fusion 360 workspace README — merged

Engineering Repository Structure

Caribou’s repository structure was expanded to support active sub-development projects. The team decided to use a top-level engineering/ area for active design work, with separate CAD and electronics sections.

For electronics, each PCB gets a self-contained folder so contributors can download/open an individual KiCad project without missing symbols, footprints, or 3D models. The first two PCB folders were created for:

  • CBC_PCB — Caribou battery connector PCB, linked to issue #6
  • CMAIN_PCB — Caribou main PCB, linked to issue #8

Each PCB folder includes subfolders for documentation, firmware, images, KiCad files, local KiCad libraries, 3D models, footprints, schematic symbols, and manufacturing outputs.

Relevant work:

  • PR #15 — Engineering project structure — merged

CBC_PCB / Battery Connector PCB

The CBC_PCB workstream was scoped as the battery connector PCB for Caribou’s 18S smart battery system. The board is intended to interface with Tattu 4.0 18S smart batteries and handle high-current battery connection requirements.

Initial requirements include:

  • 18S Tattu smart battery compatibility
  • Rectangular PCB form factor
  • 100A nominal current capability
  • 200A short-duration spike capability
  • 12V regulated output wired into the Caribou main PCB
  • Support for smart-battery communication and aircraft integration

A detailed documentation update was added covering:

  • Board overview and system context
  • Connector pinout
  • Power architecture
  • Requirements
  • Concept renderings showing the PCB and battery integration

Relevant work:

  • Issue #6 — Design BC/CBC PCB for 18S, 100A nominal, 200A spike — open
  • PR #16 — CBC PCB design notes — merged

CMAIN_PCB / Caribou Main PCB

The CMAIN_PCB workstream was opened to define a Caribou main PCB by combining useful concepts from:

  • Project Feather power distribution board architecture
  • Project Quiver main PCB architecture

The issue clarifies that CMAIN_PCB is a low-voltage, signal-level board rather than a high-current power board. Expected focus areas include flight-controller integration, six motor outputs, sensor connections, CAN bus, avionics power/regulation interfaces, and Caribou-specific form factor constraints.

Relevant work:

  • Issue #8 — Design Caribou main PCB — open

Battery Mounting System

Battery integration was one of the most active mechanical workstreams in April. The team scoped a bent sheet-metal and/or 3D-printed battery mounting system designed around the locked battery positions in the existing frame.

Key requirements included:

  • Use the current battery positions as reference
  • Primary bracket made from bent sheet metal
  • Integrate with the existing frame without welding
  • Allow battery removal for maintenance/swapping
  • Consider cable routing and reserve space for the battery connector PCB

KBM produced a first design version using 2 mm aluminum sheet-metal components, screw/washer/nut assembly, no welding, and interchangeable side-vertical components. This initial design work was reviewed and issue #9 was closed.

A follow-up frame-preparation issue was opened to remove old battery mounting brackets and repaint exposed metal areas before installing the new battery layout.

Relevant work:

  • Issue #9 — Design battery mounting bracket for Caribou frame — closed
  • Issue #14 — Remove old battery mounting brackets and touch up paint — open

Battery Connector Investigation

The team investigated the correct PCB-side connector for Tattu 4.0 18S smart batteries. The 18S connector layout differs from the 14S layout and includes four signal pins in the middle section.

Research covered multiple possible connector families and suppliers, including Molex, Samtec, Prolanv, and ACES-related references. The Prolanv PDC2110F0003 option was later found not to fit. Julius then ordered 12 pieces of a vertical Gen3 adapter and added the drawing for the ordered connector.

Follow-up tasks were created for:

  • A 3D model of the ordered ACES 59626-style 60A male battery connector
  • A KiCad schematic symbol and footprint for the same connector

Relevant work:

  • Issue #13 — Find correct PCB connector for Tattu 4.0 18S battery — open
  • Issue #17 — Create 3D model for ACES 59626 connector — open
  • Issue #18 — Create KiCad symbol and footprint for ACES 59626 connector — open

Foldable Motor Beam Connector Research

The team opened research on foldable motor arm connectors compatible with 60 mm tubes and the loads expected from Hobbywing XRotor X15 motors. The discussion considered both horizontal and vertical folding mechanisms.

Important design considerations:

  • Horizontal folding places high load on the hinge pin and has been a known failure point on Quiver.
  • Off-the-shelf horizontal 60 mm folding connectors were not found.
  • Vertical folding connectors exist, but downward folding would require impractically tall landing gear.
  • Upward folding or mid-beam folding may be more realistic options.

Relevant work:

  • Issue #7 — Research foldable motor beam connectors for 60 mm tubes — open

Caribou Hub and Telemetry System

Caribou Hub V1 was scoped as a local Linux ground-station / test-flight support application derived from Quiver Hub concepts. V1 priorities are multi-camera viewing and real-time telemetry display from ArduPilot/MAVLink.

A separate telemetry handling system issue was opened to define onboard data collection, logging, and distribution. The architecture takes inspiration from the Feather Companion Computer but adapts it to Caribou’s ArduPilot/MAVLink stack, Hobbywing XRotor X15 ESC CAN telemetry, Tattu smart-battery CAN telemetry, and Caribou Hub integration.

Relevant work:

  • Issue #10 — Caribou Hub V1 — open
  • Issue #12 — Telemetry handling system for Caribou — open

3. Goals for May 2026

  • Finish development for CBC_PCB and CMAIN_PCB.
  • Design the enclosure for CBC_PCB; design the CMAIN_PCB enclosure too if the board is ready in time.
  • Prepare the frame for the new battery layout by removing old battery mounting brackets and repainting exposed metal areas. See issue #14: Remove old battery mounting brackets and touch up paint · Issue #14 · Arrow-air/project-caribou · GitHub
  • Order sheet-metal parts for the battery holders based on the completed bracket design. See issue #9: Design battery mounting bracket for Caribou frame · Issue #9 · Arrow-air/project-caribou · GitHub
  • Continue the sensor-layout study and converge on a first integration plan.
  • Continue Caribou Hub development, with more specific application integration for Caribou use cases.
  • Continue connector integration work: complete or progress the ACES 59626-style connector 3D model, KiCad footprint, and schematic symbol. See issues #17 and #18.
  • Bench-validate the telemetry architecture with real ESC and battery CAN traffic before locking companion-computer hardware.

4. Budget & Resource Allocation

Project Expenses

Item Amount Notes
Batteries $4,924.00 5 pcs of batteries. Source: reimbursement spreadsheet

Spreadsheet: reimbursement - Google Sheets

Team Member Compensation

Team member compensation began during April. Julius project lead started on 05.04.2026, and the other team members started on 12.04.2026.

Category Amount
Team member compensation 12,867.00 USDC

Spreadsheet: Member_List_April - Google Sheets

Total April Allocation

Category Amount
Project expenses 4,924.00 USDC
Team member compensation 12,867.00 USDC
Total 17,791.00 USDC

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