1 · Economics Calculator
Extra assumptions (optional) — defaults shown; set opex to $0 and uptime to 100% for the bare 9-variable model
Weekly profit vs lbs caught per visit
Weekly profit vs operator share
What is not in this model
- Permits/registration fees, insurance, taxes, Starlink hardware (~$500 + monthly service), chase-boat fuel (that sits in the fishermen's 70%).
- Upsell not modeled: sportfishing/tourist "meet-up" charters often pay far more per trip than commercial $/lb — potentially a second, larger revenue stream.
- The two biggest levers are lbs per visit (validate in Phase 4 before scaling!) and months till USV loss (redundancy, rescue-tow, and storm retrieval drive this).
- Catch is episodic — wahoo/mahi runs can double a week, then go quiet. The average hides the variance.
2 · FAD Tow-Force Estimator
Drag: F = ½·ρ·Cd·A·v². At 0.25 mph in seawater, each ft² of effective area (Cd·A) costs ≈ 0.13 lbf. Enter the effective drag area (Cd × projected area) of everything submerged. Wave and wind gusting can spike the steady force 3–5×; the sunken anchor line adds almost nothing at this speed.
Reference: 6× Blue Robotics M200 ≈ 19 lbf each ≈ ~115 lbf combined static thrust (verify current spec sheet). Towing is cheap in watts — your real power budget goes to transit speed, hotel load (Starlink, cameras, sonar), and night lights. Measure actual force with a spring scale in Phase 3.
3 · Answers to Your FAD Questions
Have others built relocatable FADs driven by thrusters and solar power?
Not exactly this — you're in genuinely fresh territory, though close cousins exist:
- eFAD / smart-FAD buoys: satellite-tracked FADs with GPS + echo sounders (Marine Instruments, SATLINK, FiiZK, TMT) are standard in purse-seine tuna fleets. They measure and report fish but do not move the FAD.
- Solar/wind USVs: Saildrone-class vehicles have crossed oceans on renewable power, so the endurance math is proven.
- FAD tracking programs: Pacific islands and CRFM/OECS states GPS-tag anchored FADs to study usage — but the FADs themselves are stationary.
- Drifting FADs themselves: fish hold on objects drifting up to ~1–2 kn for weeks — the biological foundation your idea relies on.
A solar USV that tows/repositions artisanal FADs on a schedule — and sells meet-up info — appears to be novel (caveat: my knowledge has a cutoff). It would make a strong pilot write-up even before it turns a profit.
How much force to pull a typical artisanal FAD at 0.25 mph?
A typical artisanal FAD — your ~100 lb of rope, fronds, and floats hanging as a subsurface curtain — presents roughly Cd·A ≈ 150–400 ft². At 0.25 mph that's:
- Steady tow force ≈ 20–55 lbf
- Plan for gust/wave peaks 3–5× that when sizing thrusters and structure.
Use the estimator above with your own numbers, and verify with a spring scale in Phase 3.
How much force for an "easy-tow" FAD? Is 0.25 mph enough control vs the eddies?
Easy-tow design (single ⅜–½″ line, 6–10 small frond bundles, teardrop floats, no net panels): Cd·A ≈ 40–100 ft² → ≈ 5–15 lbf at 0.25 mph. Towing power is nearly free: ~5–10 W. Even 1 mph is only ~0.5–0.7 kW.
Currents: 0.25 mph = 0.22 kn ≈ 42 miles/week of own-steam path. Regional eddies often run 0.3–1.5 kn — faster than you. You can't fight them head-on; route with them using Copernicus Marine / OSCAR / HYCOM forecasts plus your own logged GPS drift to calibrate. Two consequences:
- "Within 40 miles of Anguilla once a week" needs a loop perimeter ≤ ~42 miles (e.g., a ~13-mile-diameter circle), or current assistance to stretch it.
- Design for short 0.5–1 kn bursts (a few hundred W) to cross adverse jets — your solar and battery can cover that.
So yes — workable as current-aware drift control, not as brute-force station keeping. A retractable drogue lets you park or let favorable currents do the work.
Is the bare 1:4 seastead an effective FAD by itself? Will fish stay if we move at 0.25 mph?
Bare model: moderately effective — better than a buoy, short of a full FAD. The 3 subsurface foils, big shade footprint, and night lights will pull in baitfish, squid, mahi, and barracuda within days. Tunas usually want more subsurface structure. Fix: add a 40–80 ft rope skirt with a few frond bundles under the center — keeps tow load ~5–15 lbf and makes it a genuine FAD.
Moving at 0.25 mph: no problem. Wild FADs drift at up to ~1–2 kn and hold fish for weeks; thruster noise at these powers is negligible (some species are even curious about structure-associated sound). Keep accelerations gentle. The retractable drogue is a great "parked mode" tool — station-keeping without bottom gear.
Underwater lights at night — worth it?
Yes — proven and cheap. Green/white LED arrays pull baitfish and squid within an hour or two (best on dark nights); predators follow within days. Budget ~100–300 W for 8–10 h/night (1–3 kWh). At 1:4 scale with ~25% of displacement in LiFePO₄ (~4–5 kWh), you can light all night and still run hotel loads. Use an astro timer and auto-dim on low battery.
How soon until there's "a good amount of fish"? What if we then start moving?
Typical build-up on a new FAD: baitfish within hours–days → mahi/barracuda/rainbow runner within days–1 week → blackfin tuna and wahoo build over ~1–3 weeks. Standing biomass usually plateaus around 2–4 weeks (echo-sounder buoy studies show the same shape). Once resident, fish routinely stay with FADs moving at up to ~1–2 kn, so starting your 0.25 mph loop should retain most of the school.
Will fish follow the FAD into shallow water? Can we lead them to the NE drop-off?
Pelagics generally won't follow onto the shallow bank (<~100 ft); the shelf edge is fine — plenty of anchored FADs live at 100–600 ft. Your plan is sound: walk the FAD to the 100–200 ft contour near the NE drop-off and park it (drogue, or tension legs at full scale). Expect some turnover crossing fronts — you won't keep 100% of the school for 40 miles — but you'll deliver a working nearshore FAD within ~12 nm of Island Harbor weekly, which is the real product. You're also effectively re-seeding a nearshore FAD every week.
Does Anguilla give a FAD owner legal protection? What about the AIS + "flee" tactic?
I can't verify Anguilla-specific rules (and my knowledge has a cutoff) — confirm with the Department of Fisheries and Marine Resources. Regionally, registered-FAD systems (Dominica, Grenada, Antigua & Barbuda, Barbados, and OECS/CRFM model guidelines) commonly grant the registered owner exclusive fishing rights within a radius (often ¼–1 nm) plus marking/registration requirements — so what you want likely exists or is negotiable, especially with DFMR as a partner.
Your AIS broadcast is a good-faith measure regulators like. The "run and starve them of fish" tactic works mechanically but is adversarial; a share system (your 30%) plus sellable meet-up info is more defensible, builds goodwill, and is probably more lucrative. Note a commercial USV also touches maritime law (COLREGs lights & watch, insurance), not just fisheries law. Consider sharing aggregate fish-abundance data with DFMR — it cements the partnership.
Rules of thumb: spacing, FAD mass, biomass, catch per visit, revisit rate
| Parameter | Typical artisanal-FAD value |
|---|---|
| Spacing between FADs | 1–3 nm (2–5 km) minimum so they don't draw from the same fish pool |
| Materials mass (floats/rope/fronds) | ~50–200 lbs (your 100 lb guess is typical); anchor line is extra weight but little drag |
| Standing biomass (good nearshore FAD, 2–4 wks) | A few hundred to a few thousand lbs (blackfin tuna, mahi, wahoo, rainbow runner, barracuda, baitfish) |
| Catch per small-boat visit | ~30–150 lbs typical; episodic spikes on wahoo/mahi runs — your 80 lb default is a fair planning number |
| Revisit rate | Every 2–4 days, weather permitting — your 3-day default matches |
Can hydrophones detect, classify, or count fish? What's an "eFAD"?
Partially. Snappers, groupers, drums/weakfish, and toadfish vocalize (often at dusk/spawning), so a hydrophone gives cheap presence/absence — and doubles as a boat detector. Tunas and mahi are mostly silent, and counting from sound is unreliable. The proven biomass tool is a small sonar — that's exactly what eFAD echo-sounder buoys do. Recommended stack: hydrophone + ~200 kHz fish-finder sonar + night camera = your sellable "fish report."
eFAD: yes, the term is established for FADs with GPS + echo sounder + satellite comms. Your additions — mobility, current-aware routing, and an info service — are the novel part.
The "carry a FAD 100 miles out, dump it, drift home" plan
Economics can work: the expensive part is transit (at 3–4 kn, hundreds of watts — check your 1:4 solar/battery budget for the round trip), deployment is free, and the drift home rides currents for free. Deploying upwind/upcurrent so drift returns it is smart. The calculator models the recurring-visit business; seed-and-drift is the same math with fewer, bigger visits — and pairs well with the dumb-FAD herd: one smart USV babysits several dumb FADs in rotation, towing each into good water, while another USV rotates home for maintenance.
The electromagnet rescue-tow system
Good concept. Three tweaks: (1) electromagnets fail-open — lose power and you lose the tow — so after magnetic capture, drop a mechanical latch/pin; (2) use a funnel guide rather than precision docking; (3) isolate the iron from aluminum (coating/plastic washers) to avoid galvanic corrosion. The same hardware then doubles as your dumb-FAD mover.
Overall — what do you think of the idea?
Genuinely promising, with honest caveats. Strengths: low capital, solar economics, the USV is itself a FAD, triple-redundant power, and two revenue streams (fish share + information). The information stream may ultimately be worth more than the fish share — it's the same data industrial eFADs monetize, sold at artisanal scale, and it costs you nothing extra to collect.
Risks that dominate the P&L:
- USV loss at sea — the single biggest economic lever (hence that slider). Redundancy, the rescue-tow system, and storm retrieval are your profit protection.
- Regulatory approval — treat DFMR as a partner from day one; share data.
- Theft/vandalism — cameras + AIS + the flee tactic; also consider low-value-looking dumb FADs.
- Hurricanes (June–Nov) — plan retrieval; budget it in "months till loss."
- Biofouling — Caribbean water fouls foils/thrusters in weeks; schedule monthly cleaning, use antifouling.
- Catch variability — validate the 80 lb/visit default with real logs before scaling.
Recommendation: start with 1 USV + 2–3 dumb FADs, instrument everything (tow force, currents, sonar biomass, catch logs), and only scale after the economics are validated at sea.
4 · Suggested Phased Test Plan (each phase can pay for the next)
- Phase 0 — Lagoon shakedown (2 wks): comms range, solar/power balance, thruster redundancy, autonomy failsafes (geofence, lost-link behavior, low-battery return).
- Phase 1 — Moored FAD trial (4–6 wks, 1–2 nm out): measure fish arrival with sonar + hydrophone + night camera; test lights; record fouling rates. Start selling "fish reports" here.
- Phase 2 — Current-aware loops (4 wks, ≤10 nm): log GPS track vs forecast currents; tune the routing model; validate the 42-miles/week budget.
- Phase 3 — Tow trials (2 wks): tow a dumb FAD; measure real force with a spring scale vs the estimator; test the magnet/latch handoff.
- Phase 4 — Full loop (8–12 wks): weekly Anguilla pass near the NE drop-off; sell meet-ups to 2–3 friendly fishermen; log lbs/visit to calibrate the calculator. This is where the model gets real numbers.
Throughout: weekly "fish report" to DFMR builds the goodwill that gets your permit renewed. Keep every log — the dataset itself has value (papers, press, grants).