Design Overview
The seastead is a trimaran-style SWATH (Small Waterplane Area Twin Hull) design with three NACA foil-shaped legs providing buoyancy. The structure features a triangular frame with 40-foot sides, a rectangular living area, and active stabilizers for enhanced wave response.
Main Frame
Equilateral triangle frame made of aluminum box beams
Living Area
12 feet wide, extending to back of triangle, 8 feet height
Buoyancy Legs
19 feet long, 10 foot chord, 2 foot width NACA foil shape
Solar Power Analysis
• Living area roof: 12 ft × 24 ft = 288 sq ft
• Fold-down panels (2 sides): 2 × (8 ft × 8 ft) = 128 sq ft
• Total solar area: 288 + 128 = 416 sq ft
• Assuming 20W/sq ft solar panels: 416 × 20 = 8,320W
Total Solar Area
Installed Solar Power
Typical Daily Yield
Caribbean conditions (4-6 peak sun hours)
Weight & Buoyancy Analysis
• Aluminum frame (40ft×3 beams + cross bracing): ~3,000 lbs
• Living area structure (walls, floor, roof): ~4,000 lbs
• 3 buoyancy legs (marine aluminum, 19ft each): ~3,600 lbs
• Netting, railings, fixtures: ~1,000 lbs
• Total structure weight: ~11,600 lbs
• Leg volume: 19 ft × 10 ft × 2 ft = 380 cu ft
• 50% submerged: 190 cu ft submerged per leg
• Buoyancy force (salt water): 190 × 64 lbs/cu ft = 12,160 lbs per leg
• Total for 3 legs: 36,480 lbs buoyancy
• Available buoyancy after structure: 36,480 - 11,600 = 24,880 lbs
Structure Weight
Total Buoyancy
Available Payload
For batteries, systems, occupants, supplies
Active Stabilizer Analysis
• Additional submerged volume per foot: 10 ft × 2 ft × 1 ft = 20 cu ft
• Additional buoyancy: 20 × 64 lbs/cu ft = 1,280 lbs per foot per leg
• For all 3 legs: 3,840 lbs per foot of additional submersion
• At 5 knots (8.44 ft/s), to generate 1,280 lbs of lift
• Using lift equation: L = 0.5 × ρ × v² × A × Cl
• Assuming Cl = 1.0 (high lift configuration)
• ρ (salt water) = 1.99 slugs/cu ft
• Required area: ~12 sq ft per stabilizer (wing + tail)
• Dimensions: ~3 ft chord × 4 ft span
Stabilizer Lift per Leg
Buoyancy adjustment per foot of water depth change
Stabilizer Wing Area
Per stabilizer (3 ft × 4 ft approximate)
Stabilizer Weight
Marine aluminum construction with actuator
Stabilizer Cost (Batch of 20)
Including actuator and control system
Wave Reduction Effect: A stabilizer system that can reduce 1 foot from wave peaks and add 1 foot in troughs effectively halves the wave action. A 4-foot wave would feel like a 2-foot wave, significantly improving comfort and stability.
Propulsion & Power Analysis
| Speed (knots) | Power Required (kW) | Range with 4000 lbs Batteries* | Wave Reduction with Stabilizers | Actual Motion (4ft wave) |
|---|---|---|---|---|
| 4 knots | 6.5 kW | 140 hours / 560 nm | ~1.2 ft reduction | ~1.0 ft movement |
| 5 knots | 12 kW | 80 hours / 400 nm | ~1.0 ft reduction | ~1.2 ft movement |
| 6 knots | 20 kW | 48 hours / 288 nm | ~0.8 ft reduction | ~1.5 ft movement |
Continuous Solar-Powered Operation: With 8.3 kW solar and 1 kW for house systems, available propulsion power is 7.3 kW. This would allow approximately 4.5 knots continuous speed 24/7 in good solar conditions. With stabilizers active (adding ~1 kW load), continuous speed would be reduced to approximately 4.0 knots.
• 40 kWh battery capacity
• Caribbean average: 5 peak sun hours/day
• Solar yield: 8.3 kW × 5 hours × 0.85 efficiency = ~35 kWh/day
• Charging time for full 40 kWh: ~1.15 days (27.5 hours of good sun)
• In practice: 1-2 days depending on conditions
Cost Estimation
| Component | Single Unit Cost | Batch of 20 Cost (each) |
|---|---|---|
| Aluminum Structure & Frame | $85,000 | $68,000 |
| Living Area Construction | $120,000 | $95,000 |
| Buoyancy Legs (3) | $45,000 | $36,000 |
| Solar Power System (8.3 kW) | $25,000 | $20,000 |
| Battery System (40 kWh) | $15,000 | $12,000 |
| RIM Drive Thrusters (6) | $36,000 | $28,800 |
| Stabilizer System (3) | $9,000 | $5,400 |
| RIB Boat & Davit | $35,000 | $28,000 |
| Systems & Electronics | $40,000 | $32,000 |
| Assembly & Finishing | $50,000 | $40,000 |
| TOTAL ESTIMATED COST | $460,000 | $365,200 |
Note: Costs are estimates for manufacturing in China and do not include design, engineering, transportation to final destination, or regulatory compliance costs. Marine-grade aluminum construction and marine systems command premium pricing even with Chinese manufacturing.
Performance Summary
Maximum Speed
With all thrusters at full power
Solar-Only Continuous Speed
24/7 operation in good conditions
Wave Response Reduction
With active stabilizers engaged
Transatlantic Crossing Time
At 4-4.5 knots continuous (3,000 nm)
Design Advantages: The SWATH configuration with NACA foil legs provides inherent stability with small waterplane area. Active stabilizers further enhance comfort by dynamically adjusting buoyancy distribution. The design balances solar-powered continuous operation with reasonable speed for ocean crossings.