This document fleshes out the "convoy mode" concept: how a group of seasteads travels together on a flexible grid, what communications hardware makes sense, and a first-cut analysis of whether a convoy can collectively reduce the wave energy felt by its members.
Convoy mode is a cooperative station-keeping and shared-situational-awareness mode. Each seastead's autopilot keeps it at an assigned grid cell relative to the convoy "lead" (or relative to the convoy's geometric centroid). Position is known to a few centimeters via moving-base RTK GPS.
CONVOY MODE ARMED. The pilot confirms; the autopilot engages.Starlink is great for off-convoy traffic, but for tight-loop control (RTK corrections at 1–10 Hz, stabilizer coordination, sub-second object track updates) you want a direct local link with predictable low latency and no dependence on a satellite uplink.
| Layer | Choice | Why |
|---|---|---|
| Primary point-to-point | Ubiquiti airMAX / LiteBeam / NanoStation 5AC, or Mikrotik LHG / SXTsq 5 (5 GHz, 802.11ac) | $70–$120 per radio, integrated dish/panel, 16–23 dBi, weatherproof, PoE. Proven in WISP use. |
| Local mesh / fallback | Wi-Fi 6 (802.11ax) omni AP on the roof, e.g. Mikrotik or Ubiquiti U6-Mesh | $150–$200. Covers the dinghy, walkway tablets, neighbors at any bearing if a directional link fails. |
| Long-range low-rate backup | LoRa (915 MHz in US) gateway + node | $30–$80. Tens of km range at ~few kbps. Carries heartbeats, GPS, "I'm alive" messages even if Wi-Fi mesh collapses in heavy spray. |
| Voice / very-long-range | VHF marine radio (already required) and optional 70 cm ham/data | Voice and emergency. Not for high-rate data. |
| Link | Realistic range over water | Throughput | Latency |
|---|---|---|---|
| 5 GHz directional, 16–23 dBi both ends | 5–15 km line-of-sight (way more than you need) | 100–400 Mbit/s | 2–8 ms |
| 5 GHz omni-to-omni | 200–500 m reliably; up to ~1 km calm | 50–200 Mbit/s | 3–10 ms |
| 2.4 GHz omni (Wi-Fi 6, backup) | 300–800 m | 20–80 Mbit/s | 3–10 ms |
| LoRa (SF7–SF10, 915 MHz) | 5–30 km over water | 0.3–20 kbit/s | 0.1–2 s |
Over water, 5 GHz behaves very well once antennas are 3–5 m above the waterline (which yours will be — the walkway is already ~1 ft above the wall bottom, plus mast). The main impairment is heavy rain and salt-fog buildup on radomes, not propagation. At 100 m grid spacing you are wildly inside the link budget; you'll be running at the radio's max modulation almost all the time.
| Item | Qty | Unit $ | Subtotal |
|---|---|---|---|
| 5 GHz directional radio (Mikrotik LHG 5 or similar) | 4–6 | ~$90 | $360–$540 |
| Wi-Fi 6 outdoor omni AP | 1 | ~$180 | $180 |
| LoRa gateway + 1 node MCU | 1 | ~$120 | $120 |
| PoE switch (8-port, outdoor-rated) | 1 | ~$120 | $120 |
| Cabling, mounts, surge protection | — | — | $150 |
| Total per seastead | ~$950–$1,150 | ||
This is small compared to the seastead itself, and it gives you fully redundant low-latency local comms.
batman-adv or babeld mesh routing
on Linux. Both handle moving nodes and broken links gracefully. batman-adv
is layer-2 and very simple; babeld is layer-3 and more flexible.chrony with GPS PPS as a reference on every
seastead. You need sub-millisecond sync for camera-parallax fusion.Short answer: a little, and only for short waves whose wavelength is comparable to or smaller than the leg diameter and spacing. For the long ocean swell that dominates motion sickness and structural loads, the effect is negligible. Let's work through it.
Each leg is a NACA 0030 foil, chord 8.5 ft (~2.6 m), max thickness 30% of chord ≈ 2.55 ft (~0.78 m). The legs are vertical, half-submerged. To a passing surface wave, the leg looks like a vertical cylinder of cross-section ~2.6 m × 0.78 m.
The relevant dimensionless parameter is k a, where k = 2π/λ
is the wavenumber and a is a characteristic radius of the leg
(call it 0.5 m). For deep-water waves, λ = g T² / (2π) ≈ 1.56 T² meters.
| Wave period T | Wavelength λ | k a (a ≈ 0.5 m) | Leg vs wave |
|---|---|---|---|
| 2 s (chop) | 6.2 m | 0.5 | Leg scatters meaningfully |
| 4 s (wind sea) | 25 m | 0.13 | Leg scatters weakly |
| 8 s (swell) | 100 m | 0.03 | Essentially transparent |
| 12 s (long swell) | 225 m | 0.014 | Completely transparent |
This is the classic result for small-waterplane-area platforms: that's the point — you chose the legs to be acoustically/hydrodynamically small compared to the swell so the platform doesn't heave with the swell. The flip side is that each leg also can't significantly scatter the swell, so a convoy of them can't shield each other from swell either.
For a vertical surface-piercing cylinder, the wave scattering cross-section σ in the long-wave limit scales like:
The practical takeaway: σ goes as k³ (or λ⁻³).
Double the wave period and you reduce the scattered power by a factor of 8.
For an 8 s swell, each leg removes essentially nothing.
For coherent shielding (like a breakwater) you'd want the spacing between scatterers to be ≤ λ/2 and the total "blockage fraction" across a row to be a substantial fraction of 1. With three legs per seastead (total frontal width ~3 × 0.78 m ≈ 2.3 m of solid leg) and 100 m grid spacing, the blockage fraction of one row is about 2%. Even with N rows you don't get coherent interference because the legs are tiny compared to swell wavelength.
You do get measurable effects in two regimes:
Treat each leg as a weak scatterer that removes a fraction f of
incident energy flux over its width. For short chop with k a ~ 0.5,
f per leg is order 0.1–0.3 of the energy passing through its
projected width. A seastead has 3 legs, total width ~2.3 m. Convoy row spacing
100 m. Energy flux removed per row ≈ 3 × 0.78 m × 0.2 / 100 m ≈ 0.5% per row.
After 10 rows, transmitted short-chop energy ≈ 0.995¹⁰ ≈ 0.95 — so ~5% energy reduction, or roughly 2.5% wave-height reduction. Honestly not much, but in beam seas with closer spacing it could reach 10–20% height reduction for short chop in the interior of a large convoy. Crew on interior seasteads would feel a calmer ride than crew on the windward edge.
| Subsystem | Function |
|---|---|
| Moving-base RTK GPS | cm-level relative position of every seastead |
| Mesh radio (5 GHz directional + Wi-Fi 6 omni + LoRa backup) | Low-latency local control plane |
| Starlink | External internet, weather, ship AIS via internet, comms with shore |
| AIS transceiver | Be visible to commercial traffic; receive their positions |
| Camera array (one per corner, plus dinghy-side) | Visual watch, parallax ranging, AI detection |
| Convoy controller software | Cell assignment, join/leave, formation maneuvers, watch coverage |
| Shared object tracker | Fused multi-seastead picture of every nearby vessel |
| Watch heartbeat | Confirms humans are actually watching |
| Shared wave-field estimator | Uses all IMUs + RTK heights to predict swell and feed each stabilizer |
| Inter-seastead walkway controller (when docked) | Coordinated thruster + stabilizer use across both units |
| Mooring-screw mode | When parked, convoy can switch to tension-leg formation as a fixed grid |
UNAFFILIATED → REQUESTED → APPROACHING → ARMED → ENGAGED → DEPARTING).