Seastead feasibility study · Solar + Kite propulsion

Circumnavigation Time Estimate:
the Westabout Trade-Wind Circuit

Downwind and downcurrent as much as physically possible, hurricanes avoided by seasonal timing rather than stopping, waves generally kept under 15 ft, and the Roaring Forties / Furious Fifties avoided entirely.

≈ 18–20 monthsNominal planning estimate

~550–600 daysUnder way (incl. small holds)

32,550 smRoute distance

~59 sm/dayBlended average (≈2.5 mph)

~70%Of time on kite power

Why go westabout (east → west)?

The planet's tropical circulation is a one-way conveyor — ride it.

In the tropics, both the winds (NE and SE trade winds) and the major surface currents (North & South Equatorial Currents, the Indonesian Throughflow, Agulhas, Benguela) flow east → west. Your kite wants downwind; your hull wants downcurrent. Going westabout stacks both bonuses for essentially the entire trip. Going eastabout in the tropics would mean fighting headwind and head-current everywhere — and the only fast eastabout option, the westerly Roaring Forties, is excluded by your wave limit.

The one exception: the Southern Ocean eastabout route (~17,500 sm, roughly 8 months, kite downwind nearly 100%) would be far faster — but it routinely serves 20–30 ft seas, so it fails your <15 ft requirement and is ruled out.

Route schematic

Canaries → Caribbean → Panama → North Pacific → Indonesia → South Indian Ocean → South Africa → South Atlantic → home. Coastlines omitted; equirectangular projection.

Speed model

Your three propulsion modes, converted to daily distance.

Mode	Speed	Daily distance
Kite, course within 30° of downwind (day or night)	3 mph	72 sm/day
Solar, sun high (6 h/day)	2 mph	12 sm
Solar, remaining 18 h	1 mph	18 sm
Solar-only day (no usable wind angle)	avg 1.25 mph	30 sm/day
Achieved route blend	≈2.5 mph	≈59 sm/day

Interpretation used: wherever the desired progress is broadly downwind, the seastead works the kite (tacking/gybing downwind at modest VMG loss where needed). On this route roughly 70% of all hours qualify — steady trades cover most of three oceans. If you forbid tacking and require the course itself to sit within 30° of true downwind at all times, add roughly 10–15% to the total time.

Leg-by-leg plan

Dates assume a October 15 departure from Las Palmas — chosen so every cyclone-prone basin is crossed in its off-season. Distances in statute miles.

#	Leg	Dist (sm)	Days	Arrive	Conditions & tactics
1	Las Palmas → Mindelo (Cape Verde)	950	14	Oct 29	NE trades astern nearly the whole way; ~95% kite.
2	Mindelo → Barbados	2,450	35	Dec 3	Classic trade-wind run, 15–20 kt aft; arrives after the Atlantic season closes Nov 30.
3	Barbados → Colón, Panama (via Curaçao)	1,350	23	Dec 25	Trades ease in the Antilles lee but stay broadly downwind.
4	Panama Canal transit	50	3	Dec 28	Queue + transit modeled as ~2 moving days + buffer.
5	Colón → Honolulu (via ~15°N)	5,300	86	Mar 23	NE trades 15–22 kt. Hold ≥18°N until past 110°W to stay north of East-Pacific genesis areas; clear of the basin before its May 15 season opening. ~76% kite.
6	Honolulu → Majuro	2,550	38	Apr 30	Steady trades plus the west-setting North Equatorial Current (~0.5 kt bonus).
7	Majuro → Guam	1,750	27	May 26	Trades; watch early-season lows forming east of Guam.
8	Guam → Surigao (Philippines) ⚠ pinch	1,600	33	Jun 29	Typhoon season ramping up. Track 5–10°N, south of the main recurvature corridor, and dodge individual systems with 5-day forecasts.
9	Philippine inland seas → Sulu Sea ⚠ pinch	700	17	Jul 15	Archipelago calms and squalls; solar-heavy stretch.
10	Sulu Sea → Makassar Strait → Lombok	1,000	22	Aug 7	SE monsoon sets in = tailwind southbound; Indonesian Throughflow current aft (1–2 kt in the straits).
11	Lombok → Chagos	3,100	47	Sep 23	Austral-winter SE trades 15–25 kt, dead downwind; ~86% kite. Zero South Indian cyclone risk (season opens mid-Nov).
12	Chagos → Mauritius	1,150	18	Oct 11	Same regime, riding the South Equatorial Current; exits before cyclone season.
13	Mauritius → Tôlanaro (S. Madagascar)	550	10	Oct 21	Trades with East Madagascar Current assistance.
14	Mozambique Channel → Maputo ⚠ pinch	900	17	Nov 7	Mozambique Current 1–2 kt aft but squally; sprint through ahead of the cyclone-season peak.
15	Maputo → Durban → Cape Town ⚠ pinch	900	16	Nov 23	Agulhas Current 2–4 kt aft, then westerly headwinds at the corner. Wait for a 3–4 day forecast window; hug the coast. Briefly the coldest, roughest water of the trip.
16	Cape Town → Walvis Bay	800	13	Dec 6	Benguela Current plus coastal SSE winds aft — a gift after the corner.
17	Walvis Bay → Ascension	2,200	33	Jan 8	Open-water SE trades, broad reach; South Equatorial Current.
18	Ascension → Fortaleza	1,950	30	Feb 7	Trades; South Atlantic tropical cyclones are exceedingly rare.
19	Fortaleza → Barbados → Las Palmas	3,300	69	Apr 17	Slow ITCZ/doldrums crawl near 5–10°N (solar-only), then NE trades carry you home.
Total		32,550	549	~18.1 mo	≈59 sm/day blended average

For reference, a bare parallel at 15° latitude is only ~24,000 sm around — the extra ~8,500 sm here buys meridional positioning, the archipelago route through Indonesia, and the unavoidable Africa corner.

18-month timeline

Proportional to days per phase, departing Oct 15.

71d

150d

72d

75d

47d

132d

Oct 15 mid-Jan mid-Apr mid-Jul mid-Oct mid-Jan mid-Apr (yr+1)

Atlantic out Canal North Pacific Indonesia / Philippines Indian Ocean Africa corner South Atlantic home

Hurricane / cyclone avoidance calendar

With live forecasting, storms are dodged tactically; the schedule keeps you out of each basin's statistical season entirely.

Basin	Official season	Our exposure	Tactic
North Atlantic	Jun 1 – Nov 30	Caribbean crossed in Dec	Depart Canaries mid-Oct; arrive after season close.
East North Pacific (most active per unit area on Earth)	May 15 – Nov 30	Crossed Feb–Mar at 15–20°N	Stay north of the main genesis band; fully clear before May 15.
West North Pacific (typhoons)	Peak Jul–Oct	Guam late May; Philippines Jun–Jul	Track 5–10°N, south of the recurvature corridor; forecast-dodge the early-season systems. Highest residual risk of the trip.
North Indian Ocean	Apr–Jun & Oct–Dec	Never entered	Route stays south of 8°N — avoided by design.
South Indian / Australian	Nov 15 – Apr	Crossed Aug–Oct	Austral winter = strongest, most reliable trades and no cyclones.
South Pacific	Nov – Apr	Not visited	Northern Pacific route avoids it entirely.
South Atlantic	(very rare events)	Crossed Dec–Feb	Negligible; expect only ITCZ squalls near the equator.
Agulhas corner	Extratropical lows year-round	Late Nov	Not a tropical system issue — wait for a forecast window; worst-case a few days of holding.

Residual risks: the Philippine Sea in June–July and the Mozambique Channel in early November are the two places where an unlucky season could force multi-day holds. Both are priced into the conservative scenario below.

Scenarios

The spread is driven almost entirely by one variable: what fraction of hours the kite can actually work.

Physics floor 452 days · ~15 mo Every mile at 3 mph kite speed. Unreachable idealization — useful only as a lower bound.

Optimistic ~500 days · ~16.5 mo Persistent trades, generous current/eddy surfing, no holds, quick canal transit. Kite uptime ~84%.

Nominal ★ ~550 days · ~18 mo The schedule tabulated above. Kite uptime ~70%, normal squall slowdowns, typical current credits.

Recommended planning number ~600 days · ~20 mo Adds canal queues, Agulhas weather windows, forecast-driven detours, and a couple of storm holds.

Conservative ~690 days · ~23 mo Strong El Niño disrupts trade patterns; repeated typhoon-season holds; kite uptime drops to ~40–50%.

Assumptions, sensitivities & fine print

Kite interpretation: 3 mph is available on any course within 30° of true downwind, including tacking/gybing downwind at reduced VMG. A stricter reading adds ~10–15%.
Currents: mean equatorial currents (~0.5–1 kt) are credited modestly on the long ocean legs. Mesoscale eddies (your real-time altimetry via Starlink) are worth another ~2–4% on open-ocean legs — already partly reflected in the optimistic case.
Waves: the tropical route typically sees 6–12 ft trade-wind seas. The only place likely to exceed 15 ft is the Agulhas corner — crossed in a chosen window, close ashore, and it lasts under three weeks of the whole voyage.
Suez alternative rejected: the Red Sea northbound is dead upwind — ~1,300 sm at solar-only 30 sm/day ≈ 43 extra days, plus canal fees. The Cape route wins even with its weather windows.
Storm avoidance costs speed, not stops: detours around forecast systems are the norm; full stops are rare and short. Provisioning, repairs, and sightseeing are excluded per your instructions.
Biggest lever: kite uptime. Each ±10 percentage points of kite-time moves the total by roughly ∓75 days. Everything else is second-order.
Overall confidence: treat the result as ±20% — i.e., plan on 18–20 months, be delighted with 16.5, and don't promise anyone better than 23.

Circumnavigation Time Estimate:the Westabout Trade-Wind Circuit