A solar-powered, foil-legged floating habitat designed to fit all structural parts inside a single 40-foot shipping container for rapid deployment in the Caribbean.
This seastead uses a Small Waterplane Area Tri-Hull (SWATH) concept. A large equilateral-triangle platform sits high above the water on three NACA 0030 foil-shaped legs — one at each vertex. Because the legs present only a small cross-section to the water surface, wave-induced motion is dramatically reduced compared with a conventional hull, producing a soft, stable ride even in moderate seas.
Top-down view — not to scale. All three legs are NACA 0030 foils oriented with the blunt (leading) edge forward.
| Parameter | Value | Metric |
|---|---|---|
| Platform shape | Equilateral triangle | 38 ft / side |
| Total footprint area | 626 sq ft | 58.1 m² |
| Interior living area | 595 sq ft | 55.3 m² |
| Truss height (floor → ceiling) | 7 ft | 2.13 m |
| Number of legs | 3 | — |
| Leg foil section | NACA 0030 | — |
| Leg chord | 7.5 ft | 2.29 m |
| Leg max thickness | 2.25 ft | 0.69 m |
| Leg length (total) | 18 ft | 5.49 m |
| Draft at base operating weight | 5.9 ft | 1.79 m |
| Freeboard (platform above water) | ~12 ft | ~3.7 m |
| Solar peak power | 9.0 kW | — |
| Daily solar production (Caribbean) | 44 kWh | — |
| Battery capacity (base) | 50 kWh | LiFePO₄ |
| Thrusters | 6 × rim-drive | 30 kW total |
| Stabilizers | 3 servo-tab units | — |
| Metacentric height (GM) | ~50 ft | ~15 m |
| Container required | 1 × 40-ft (FEU) | — |
| Assembly time estimate | 2–4 weeks | 4–6 person crew |
The living platform is an equilateral triangle with 38-foot sides, yielding a total footprint of 626 sq ft (58.1 m²). After accounting for the thin-wall construction, the usable interior measures approximately 595 sq ft — comparable to a generous one-bedroom apartment.
Each side of the triangle is a 7-foot-deep Warren truss (floor-to-ceiling), providing both structural depth and the wall framework. Each 38-foot side ships as two 19-foot bolted segments. The truss members are:
Interior flooring uses a combination of ³⁄₁₆″ aluminum checker plate in high-traffic and wet areas, and lighter composite/marine-plywood panels elsewhere. Floor joists span the interior at roughly 3-foot spacing, supported by the bottom chords of the perimeter truss.
Walls are a lightweight aluminum tube frame infilled with plexiglass (acrylic) windows on the upper two-thirds and solid ⅛″ aluminum panels on the lower third. Approximately 50% of the total wall area is glazed, providing panoramic ocean views from the living space. Wall thickness is roughly 6 inches — just enough for the frame, insulation, and panel attachment.
The roof is a flat aluminum deck (⅛″ sheet with stiffening ribs) supported by purlins spanning between the top chord and a center ridge structure. The entire upper surface is available for solar panel mounting.
Three vertical foil legs provide all buoyancy. Each leg is a NACA 0030 symmetric airfoil shape — 7.5-foot chord, 2.25-foot maximum thickness, and 18-foot total length. The legs are oriented with the blunt (leading) edge facing forward, producing low hydrodynamic drag when the seastead is underway.
| Foil family | NACA 0030 |
| Chord (c) | 7.5 ft (2.29 m) |
| Max thickness (t) | 2.25 ft (0.69 m) |
| t/c ratio | 30% |
| Cross-section area | 11.56 sq ft |
| Volume per leg | 208.1 cu ft |
| Total 3-leg volume | 624.3 cu ft |
Each leg is built from aluminum ribs, stringers, and skin:
At base operating weight (~5.9 tonnes), the draft is only 5.9 ft — roughly 33% of the leg length. This places the living platform about 12 ft above the waterline, well clear of typical wave crests. The SWATH waterplane area is a mere 34.7 sq ft, so the seastead is nearly immune to short chop.
At maximum designed payload (50% submersion), the draft reaches 9 ft — still leaving 9 ft of freeboard on the legs. Reserve buoyancy is enormous: over 50% of total leg volume remains above water even at full load.
Six rim-drive electric thrusters provide propulsion and maneuvering. Each thruster has a 1.2-foot (14.4″) diameter, with the flat face oriented fore-and-aft for minimal drag when not in use.
| Cruising speed (eco) | 3 knots |
| Power at 3 kn | ~4 kW |
| Range at 3 kn (50 kWh battery) | ~37 NM |
| Max speed (all thrusters) | ~6–7 knots |
| Power at 6 kn | ~15 kW |
Range is battery-only. Solar recharging extends range for island-hopping.
Each main leg has a servo-tab stabilizer mounted near its aft end — essentially a small underwater airplane that damps pitch and roll motions.
| Main wing span | 10 ft |
| Main wing chord | 1.2 ft |
| Fuselage length | 5 ft |
| Elevator span | 2 ft |
| Elevator chord | 6 in |
The servo-tab principle uses a small actuator on the elevator to change the angle of attack of the main wing — a large hydrodynamic force is produced with only a tiny control input. At 5 knots each stabilizer generates over 450 lbs of corrective force.
A pivot fitting notches into the thin trailing edge of the NACA 0030 leg — the notch only needs to reach ~25% of the stabilizer wing chord.
The 626 sq ft roof is covered with high-efficiency monocrystalline panels. After deducting structural overlaps and access walkways, approximately 500 sq ft of active panel area is available.
| Parameter | Value |
|---|---|
| Panel area | ~500 sq ft |
| Panel efficiency | ~20% |
| Peak power (STC) | 9.0 kW |
| Caribbean peak sun hours (annual avg) | 5.5–6.0 hrs |
| System efficiency factor | 0.85 (temp, wiring, inverter) |
| Daily production | ~44 kWh |
| Configuration | Capacity | Weight |
|---|---|---|
| Base | 50 kWh | 1,040 lbs |
| Extended | 100 kWh | 2,080 lbs |
| Maximum (using payload) | ~200 kWh | 4,160 lbs |
LiFePO₄ (lithium iron phosphate) chemistry is selected for safety, cycle life (>3,000 cycles), and tolerance of high temperatures. The base 50 kWh bank stores roughly one full day of solar production.
| Load | Watts | Hrs/Day | kWh/Day |
|---|---|---|---|
| LED lighting (interior + exterior) | 100 | 6 | 0.6 |
| Refrigeration / freezer | 120 | 24 | 2.9 |
| Navigation electronics | 50 | 24 | 1.2 |
| Starlink internet | 75 | 12 | 0.9 |
| Induction cooktop | 1,800 | 1 | 1.8 |
| Water maker (400 GPD) | 400 | 2 | 0.8 |
| Ventilation fans | 60 | 12 | 0.7 |
| Water heater | 1,500 | 0.5 | 0.8 |
| Entertainment / misc | 100 | 4 | 0.4 |
| Total consumption | ~10 kWh | ||
| Surplus available | ~34 kWh |
| Component | lbs | kg |
|---|---|---|
| STRUCTURE | ||
| Triangle truss frame (3 × 38-ft sides) | 2,900 | 1,315 |
| Floor (aluminum plate + composite) | 1,200 | 544 |
| Walls (frame + aluminum panels + plexiglass) | 1,300 | 590 |
| Roof panels (aluminum) | 700 | 318 |
| 3 Leg foil structures | 1,100 | 499 |
| 3 Stabilizer assemblies | 180 | 82 |
| 6 Rim-drive thrusters + mounts | 360 | 163 |
| Ladders (3, built into legs) | 90 | 41 |
| Hardware, brackets, misc structure | 450 | 204 |
| Structural Subtotal | 8,280 | 3,756 |
| SYSTEMS | ||
| Solar panels (9 kW) | 500 | 227 |
| Wiring, inverter, BMS, bus bars | 200 | 91 |
| Batteries — 50 kWh LiFePO₄ | 1,040 | 472 |
| Plumbing (tanks, pumps, piping) | 300 | 136 |
| Fresh water (100 US gallons) | 834 | 378 |
| Systems Subtotal | 2,874 | 1,304 |
| INTERIOR FITOUT | ||
| Galley (counters, sink, induction stove) | 250 | 113 |
| Head (marine toilet, shower) | 200 | 91 |
| Bed / sofa / table | 300 | 136 |
| Storage, cabinets, flooring finish | 250 | 113 |
| Interior Subtotal | 1,000 | 454 |
| CREW & PROVISIONS | ||
| 2 adults | 350 | 159 |
| Food (1 month) | 300 | 136 |
| Personal items | 200 | 91 |
| Crew Subtotal | 850 | 386 |
| TOTAL BASE OPERATING WEIGHT | 13,004 | 5,900 |
| Parameter | Value | Notes |
|---|---|---|
| Max displacement (50% submersion) | 19,975 lbs (9.1 t) | 312 cu ft displaced |
| Base operating weight | 13,004 lbs (5.9 t) | Full crew & stores |
| Draft at base weight | 5.9 ft (1.79 m) | 33% leg submersion |
| Freeboard at base weight | 12.1 ft (3.69 m) | Platform above waterline |
| Available payload | 6,971 lbs (3.2 t) | To reach 50% submersion |
The SWATH trimaran configuration provides extraordinary stability. The three legs are spaced ~19 ft from the platform center, creating a wide base of support that resists roll and pitch.
| Stability Parameter | Value | Significance |
|---|---|---|
| Total waterplane area | 34.7 sq ft | Very small — wave insensitivity |
| Waterplane 2nd moment (I) | 12,700 ft⁴ | Wide leg spacing dominates |
| Metacentric height (GM) | ~50 ft | Extremely stiff in roll |
| Heave stiffness | 2,220 lbs/ft | 1 tonne → only 1 ft of sinkage |
| Reserve buoyancy (>50% of leg volume) | >9 tonnes | Enormous safety margin |
In practical terms: the seastead barely responds to short-period waves (which it essentially ignores thanks to the tiny waterplane), and the wide leg spacing means even large, slow swells produce only gentle, slow motions. The three stabilizers actively damp whatever residual motion remains.
For stationary deployment, three helical (screw) anchors are installed on the seabed — one forward, two aft — connected by vertical tension legs (high-strength synthetic line or chain) to attachment points at the base of each leg. Winches on the platform adjust tension for varying conditions.
Two seasteads can connect stern-to-stern using a lightweight aluminum gangway (8–12 ft long, with non-slip decking and flexible universal joints at each end). When connected, people can walk safely between seasteads, enabling a real floating community. The walkway stows flat on the aft deck during transit.
A 14-ft RIB dinghy is secured sideways against the center of the aft edge, supported by two cantilevered aluminum beams and secured with quick-release lines. When the seastead is underway, the dinghy is shielded from wind and spray by the living area.
All structural parts, hardware, and selected systems fit inside a single standard 40-foot (FEU) shipping container with significant room to spare. This allows the Chinese shipyard to load everything into one container for ocean freight to the Caribbean.
| Item Category | Qty / Notes | Packed Volume | Weight |
|---|---|---|---|
| Truss chord segments (19 ft tubes) | 12 pcs | 60 cu ft | 1,800 lbs |
| Web members, gussets, splice plates | ~300 pcs | 50 cu ft | 1,100 lbs |
| Floor panels | 10 panels | 25 cu ft | 1,200 lbs |
| Wall frame members | various | 40 cu ft | 550 lbs |
| Wall panels (aluminum + plexiglass) | stacked flat | 40 cu ft | 750 lbs |
| Roof panels | stacked flat | 20 cu ft | 700 lbs |
| Leg ribs (NACA 0030 cutouts) | 30 pcs | 15 cu ft | 450 lbs |
| Leg stringers + bulkheads | ~27 pcs | 12 cu ft | 200 lbs |
| Leg skin panels (flat sheets) | 6 sets | 10 cu ft | 450 lbs |
| Stabilizer components | 3 sets | 10 cu ft | 180 lbs |
| Thrusters | 6 units | 15 cu ft | 360 lbs |
| Ladders + misc brackets | — | 10 cu ft | 200 lbs |
| Hardware box (fasteners, seals, hinges) | — | 8 cu ft | 350 lbs |
| TOTAL IN CONTAINER | 315 cu ft | 8,290 lbs |
The estimate below is based on marine aluminum fabrication at a Chinese coastal shipyard with CNC cutting and robotic welding capabilities, for a firm order of 10 seasteads delivered at once.
| Line Item | Per Unit (USD) | Notes |
|---|---|---|
| Marine aluminum 5083 (material) | $12,000 | ~4 tonnes inc. cutting waste |
| CNC plasma / laser cutting | $1,800 | ~35 machine hours |
| Robotic MIG/TIG welding | $2,200 | ~40 machine hours |
| Manual welding & fit-up | $3,500 | ~80 skilled labor hours |
| Plate forming & bending | $800 | Leg skins, curved panels |
| Surface treatment (primer) | $2,000 | Chemical wash + marine primer |
| Plexiglass (acrylic) panels | $1,200 | ~300 sq ft, ½″ thick |
| SS hardware (fasteners, hinges, seals) | $2,000 | 316 stainless steel |
| Quality control & inspection | $800 | Dye penetrant, dimensional check |
| Engineering (amortized ÷ 10) | $3,000 | Detail drawings, jigs, prototype |
| Packaging & container loading | $500 | Blocking, bracing, wrapping |
| Subtotal | $29,800 | |
| Shipyard margin (15%) | $4,470 | |
| TOTAL STRUCTURAL — Per Seastead | ~$34,000 | Range: $30k – $38k |
| TOTAL STRUCTURAL — 10 Seasteads | ~$340,000 |
Excludes solar panels, batteries, thruster motors, interior appliances, dinghy, and shipping from China to the Caribbean.
| Category | Est. Cost (USD) | Notes |
|---|---|---|
| Structural parts (Chinese shipyard) | $34,000 | Aluminum, plexiglass, hardware |
| Solar panels (9 kW, rigid monocrystalline) | $9,000 | $1.00/W, marine mounting hardware |
| Battery system (50 kWh LiFePO₄ + BMS) | $12,000 | $240/kWh installed |
| Rim-drive thrusters (6 units) | $12,000 | $2,000 each (Chinese mfg) |
| Stabilizer actuators & hardware | $1,000 | Linear actuators, pivots |
| Electrical systems (inverter, wiring, panels) | $5,000 | Marine-grade throughout |
| Plumbing & water systems | $2,500 | Tanks, watermaker, pumps |
| Interior fitout (galley, head, furniture) | $5,000 | Lightweight marine grade |
| Mooring system (3 helical screws + tension legs) | $3,000 | Dyneema® lines, winches |
| 14-ft RIB dinghy | $5,000 | Hypalon, rigid floor |
| Yamaha HARMO electric outboard | $10,000 | Integrated steering + power |
| Container shipping (China → Caribbean) | $4,000 | One-way ocean freight |
| Import duties & taxes (~5%) | $5,000 | Varies by destination country |
| Assembly labor (4 weeks × 5 people) | $12,000 | Local Caribbean labor |
| Contingency (10%) | $11,950 | |
| COMPLETE SEASTEAD — Per Unit | ~$131,000 | Range: $115k – $150k |
Estimated assembly time: 2–4 weeks with a crew of 4–6 people (including at least one certified aluminum welder for on-site finishing).
This MVP demonstrates the core SWATH trimaran seastead concept at minimum cost. Future iterations can scale up:
| Parameter | Value |
|---|---|
| Platform shape | Equilateral triangle, 38 ft per side |
| Total footprint / interior area | 626 / 595 sq ft |
| Floor-to-ceiling height | 7 ft |
| Wall glazing ratio | ~50% plexiglass |
| Hull type | SWATH — 3 × NACA 0030 foil legs |
| Leg dimensions (chord × thickness × length) | 7.5 × 2.25 × 18 ft |
| Draft (base) / Max draft | 5.9 ft / 9.0 ft |
| Freeboard (platform above water) | ~12 ft |
| Max displacement (50% submersion) | 19,975 lbs (9.07 tonnes) |
| Base operating weight | 13,004 lbs (5.90 tonnes) |
| Available payload | 6,971 lbs (3.16 tonnes) |
| Solar peak power | 9.0 kW (500 sq ft) |
| Daily solar production (Caribbean) | ~44 kWh |
| Battery (base / max) | 50 kWh / ~200 kWh |
| Daily consumption (typical, no A/C) | ~10 kWh |
| Thrusters | 6 × 5 kW rim-drive (30 kW total) |
| Cruising speed / range | 3 kn / ~37 NM (battery) |
| Stabilizers | 3 × servo-tab hydrofoil |
| Roll stability (GM) | ~50 ft (extremely stable) |
| Mooring | 3 × helical screw + tension legs |
| Tender | 14-ft RIB + Yamaha HARMO |
| Shipping | 1 × 40-ft container |
| Assembly time | 2–4 weeks (4–6 crew) |
| Structure cost (10-unit order) | ~$34,000 / unit |
| Complete cost (all-in) | ~$131,000 / unit |