2026‐08 - Arrow-air/project-caribou GitHub Wiki

August 4, 2026

Caribou Call — Recording · HearHear transcript

Attendees: far1no, errrks.eth, thomasg, kbmollysuh, sleety.eth

• PT1 Fully Assembled — Ground Testing Went Well

  • Caribou is fully assembled and last week's testing went well with no major problems. It is powerful and notably quiet — a small DJI hovering above it was louder; the props run at a deeper, less intrusive tone.
  • Motor RPM stayed in the same range despite the batteries sitting at different charge levels.
  • Two small issues: the Cube node's Ethernet adapter intermittently crashes (suspected cause: mounting too close to the antenna), and battery 6's telemetry displayed zero in Mission Planner's data window without any unhealthy-battery notification — logs to be checked to see whether it's a display issue.
  • One small CBC PCB fix is wanted before anyone else orders boards; issue still to be filed.

• First Flight Moves Into Phase 2 — Done Legally

  • Julius will file for a German authority approval allowing testing at the same location for up to two years. Stated processing time is a few weeks, faster where danger is low — likely applicable (private, secured, sparsely populated field).
  • Motivation stated plainly: the repo has attracted too many eyes (~75) to fly informally. Thomas agreed — more organized than the Feather PT1 days.
  • Pre-flight tests that need no approval continue meanwhile: folding motor-arm connectors attached this week, another ground test with them fitted, and a battery rundown test from 100% to cutoff.

• Phase 1 → Phase 2

  • The July progress report is published. The Phase 2 document posts shortly for feedback, followed by a new Snapshot proposal with adjusted phases. Thomas remains eager to build a Texas prototype in Phase 2.
  • A light website-docs status pass happens at Phase 1 close (full documentation remains later-phase scope).
  • Remaining Phase 1 funds stay in the Caribou multisig until the Phase 2 Snapshot, usable for wrap-up and documentation.
  • The design goes into the repo: Fusion → STEP export (Thomas offered AI-assisted help converting toward build123d). Signal cables are absent from the CAD; acceptable so long as the structure is there.
  • Issues cleanup: most stale or finished issues closed.

• PEEK Machined Parts (KBM)

  • Proposal: CNC-machined PEEK (printed PEEK considered unreliable; PEEK stock is cheap) starting with the folding motor-beam mechanism, later possibly landing gear and beam joints — and eventually Quiver's center beam, top plate or attachment interface.
  • KBM's recalled figures (unverified, from a supplier exhibition and test data): CF-filled PEEK approaches aviation aluminum alloy strength; pure PEEK is roughly 30–35% of aluminum's strength at about 20% of the weight. Advantage is weight; trade-off is larger part sizes unless fiber-filled.
  • Agreed path: Julius models the purchased folding beam connector → KBM adjusts → KBM gets CNC quotes (China-first on cost) → compare against the bought aluminum part and metal 3D printing.
  • IP note: the model is measured from a purchased Chinese part. Practical enforcement in Chinese UAV parts is near-nil, and Thomas sees a well-made machined adapter as a potential Arrow-shop product — the IP question deserves a proper look before that step.

• Open Items

  • Julius: post the Phase 2 document for feedback, then the Snapshot proposal.
  • Julius: file the German site-approval application.
  • Julius: check battery-6 telemetry logs; investigate the Ethernet-adapter crashes.
  • Julius: folding motor-arm connectors on, ground test with them, battery rundown test.
  • Julius: file the CBC PCB fix as an issue; export STEP to the repo; light website-docs status update.
  • Julius: model the folding beam connector for KBM.
  • KBM: adjust the model, source PEEK CNC quotes, compare costs.

• Open Questions / Risks

  • The approval timeline (weeks) now gates the first flight; no fallback was discussed.
  • Battery-6 telemetry and the Ethernet crashes are open reliability items going into approval.
  • PEEK strength figures need verification against datasheets before designing to them; the copy-part IP question needs a real answer before any shop product.

August 11, 2026

Caribou Call — recording not yet posted · HearHear transcript

Attendees: far1no, errrks.eth (from the Texas meetup), sidereal_night (new), kbmollysuh (mic broken)

• Status

  • Main ask: review the Phase 2 proposal.
  • Folding arm connectors: 4 of 6 attached; the body connector gets CADed before the last ones go on so the model stays complete. Inner frame is steel (easy to manufacture, prototype-appropriate), arms aluminum.
  • Longshot battery: first pack prototype assembly planned this month.

• New Contributor: sidereal_night

  • Referred by Ben (WhiteDadJokes). Self-reported background: flight control, navigation and communication focus; heavy-lift agricultural drone work in Baden-Württemberg (hilly-terrain flight control); an upcoming heavy-lift project stacking power-grid tower elements in Ecuador. Long-time Germany resident (knows Julius's region), now in Spain.
  • Arrived prepared — had read the Caribou channels and PT2 forum proposals — and asked precise questions about the design envelope. Outcome: he will propose PT2 inner-frame designs and continue with Julius over DM/calls. Julius asked to see his heavy-lift project plans in return.

• PT2 Design Envelope (as stated on the call)

  • Phase 2 upgrades the current layout; the core frame is the main change (Julius still owes his own core-frame proposal).
  • Keep: 6× Tattu 18S 30 Ah (one per motor), the battery PCB + enclosure, and the main PCB enclosure mid-frame.
  • Open: carbon fiber tubes (possibly larger), honeycomb structures, 3D-printed aluminum parts within size limits. The steel inner frame will go.
  • Primary optimization: weight. No drag requirement; flight time is whatever the Tattus give.
  • Tank/dispenser: DJI Agras T40 integration is an off-the-shelf option, not a hard requirement; real volumetric need is ≤150 L (Nils's 200 L was a placeholder).

• Open Items

  • All (esp. Erick): review the Phase 2 proposal.
  • Julius: CAD the body connector; attach the final folding-arm connectors; draft his core-frame proposal.
  • sidereal_night: inner-frame design concepts within the envelope; share his project plans.

• Notes

  • The ArcPad group, who said on Aug 7 they would attend, did not appear.
  • KBM's microphone failed; his input was lost this call.

August 25, 2026

Caribou Call — recording not yet posted · HearHear transcript

Attendees: far1no, errrks.eth, kbmollysuh, thomasg (late)

• Phase 2 Snapshot Is Live

  • Posted Aug 24, closes Sep 1 so Phase 2 starts fresh with September. Participation is thin (~4 votes); forum feedback was quiet beforehand. Please vote.

• Ethernet/GPS Interference — Cross-Project Update

  • Erick's obstacle-avoidance flight test 1 of 4 passed (top LiDAR only), and with the Ethernet switches removed his M9N performs fine again.
  • Complication: Julius has flown the same switches on the same PCB (Kestrel) with no M9N issues — the failure isn't universal. Symptoms on the record from Erick's builds: very slow/no acquisition, fix oscillation between 3D Fix and DGPS, velocity spikes, and up to ~1 km disagreement between the two GPSs before settling.
  • A magnetometer angle emerged: after KBM-recommended recalibration (switches removed), the aircraft flew better — the original calibration may have been distorted by switch EMI, or it simply needed a recal.
  • Mitigations: standoffs ordered; grounded bottom-plate shielding considered; if neither works, reposition the M9N (Julius's recommendation — far less rewiring than moving switches). Julius sends Kestrel logs for comparison. Caribou's own M9N is disabled (two-GPS limit) so it can't arbitrate.
  • Conformal-coating note: the bare rectangle around Ethernet connectors is deliberate masking, not delamination.

• German Flight Approval

  • The site-approval application is submitted for an untethered testing campaign (tethered vs untethered barely differs — safety distances apply regardless). Receipt confirmed; fast-track; "a few weeks."

• Testing and Design

  • Planned: full battery rundown ground test — 100% capacity at ~45–50% throttle, measuring endurance.
  • Julius continues iterating his PT2 core-frame design proposal.

• Documentation Plan

  • Deliberately no assembly guide for PT1 ("we will never build it like this again") — instead a PT1-report-style platform overview: materials, folding adapters, empty-weight characteristics, anticipated performance.
  • Erick updates his early Caribou electrical-architecture doc to match the real prototype.
  • Julius's operator's manual (built from the official German agency template) gets personal info scrubbed and published — maintenance intervals, pre/post-flight checklists, flight-area definitions. Erick will borrow from it for the Quiver Pilot's Handbook and check for an FAA equivalent.

• Longshot (side update)

  • Pack assembly underway (pictures in Longshot general; the clear case is inspection-friendly). Spot welding with the new welder expected imminently; laser welding and ultrasonic wire bonding noted as the alternatives. Cells are low-self-discharge and the v0 PCB won't drain packs. A November battery-assembly session was floated; Thomas is getting a spot-welder shopping list.

• Open Items

  • All: vote on the Phase 2 Snapshot (closes Sep 1); Thomas owes forum comments.
  • Julius: Kestrel logs to Erick; battery rundown test; core-frame iterations; operator's-manual publication.
  • Erick: electrical-architecture doc update; OA flight tests 2–4; M9N standoffs/shielding.

• Open Questions / Risks

  • Low vote participation with a week to run.
  • The interference root cause is open — confirmed by removal in two builds, contradicted by a third; the Kestrel logs discriminate.
  • The approval clock now runs against the first-flight weather window.