Based on specifications from http://seastead.ai/ai/seastead.goals.html
Leg Dimensions: 24ft long, 3.9ft diameter. Submerged length ~16ft. Wall thickness varies by choice.
| Attribute | Option 1: Duplex Stainless 2205 | Option 2: Marine Aluminum (5083/6061) |
|---|---|---|
| Thickness (Side/Ends) | 0.25" / 0.5" | 0.5" / 1.0" |
| Est. Weight (3 Legs) | ~18,500 lbs | ~6,800 lbs |
| Est. Material Cost (Raw) | ~$15,000 - $20,000 | ~$8,000 - $12,000 |
| Life Expectancy | 50+ years (Excelllent corrosion resistance) | 30-50 years (Requires monitoring/anodizing) |
| Recommendation | Indestructible, but very heavy. | Recommended. Significant weight saving improves stability, motion, and reduces cost. Easier to ship. |
3 Cylinders, Diameter 3.9ft, Submerged Length 16ft.
The main triangle frame is 50ft per side. The legs go out at 45 degrees from corners.
The submerged "loop" of cable forms a smaller triangle. Assuming the leg attachment points are roughly 20ft inward from the corners at the waterline (due to the 45-degree angle and length), the bottom cable triangle is approximately 30-35ft per side.
The body is a pyramid. Base 50ft, Height 25ft. Total surface area is roughly 2,800 sq ft. 80% coverage = 2,240 sq ft of panels.
Panel Spec: Standard 300W residential panel is ~17 sq ft. (17 sq ft * 2,240 = 132 panels). Or use thin film for better angle integration.
Requirement: Store 2 days of energy.
| Item | Watts (Avg) | Notes |
|---|---|---|
| AC (1 unit running) | 1,500 | Intermittent |
| Fridge/Appliances | 400 | Continuous |
| Lighting & Electronics | 200 | Continuous |
| Water Makers | 500 | 1-2 hrs/day |
| Total House Load | ~2,600 Wh (Avg 110W) | Over 24h |
Surplus for Propulsion: With ~180kWh generated and ~40kWh used, you have ~140 kWh (140,000 Wh) available for propulsion daily.
Note: Solar production varies wildly by weather. Winter generation might be 30% lower.
4x Submersible Mixers (3kW each). Total 12kW thrust potential.
At 0.5 to 1 MPH (0.44 to 0.88 ft/s), drag is very low.
Calculating drag on the Pyramid structure (Triangle ~1300 sq ft frontal area projection) + Cables/Legs.
| Wind Speed | Drag Force | Power to Hold Station |
|---|---|---|
| 30 MPH | ~450 lbs | ~3,000 Watts |
| 40 MPH | ~800 lbs | ~7,000 Watts |
| 50 MPH | ~1,250 lbs | ~14,000 Watts |
Analysis: At 30mph, you can hold station on solar alone. At 50mph, you would drain batteries rapidly or drift. The "Sea Anchor" is crucial here (see Storm section).
Estimates based on Aluminum legs (recommended) and standard market rates.
| Item | Est. Weight (lbs) | Est. Cost (USD) | Notes |
|---|---|---|---|
| 1. Legs (Alum) | 6,800 | $25,000 | Fab + Materials | 2. Body (Frame + Cladding) | 5,000 | $30,000 | Steel/Alum frame |
| 3. Tensegrity Cables | 300 | $2,000 | Dyneema (or SS if Al legs) |
| 4. Motors & Controllers | 600 | $20,000 | 4x Mixers + controllers |
| 5. Propellers | Included | Included | Part of mixers |
| 6. Solar Panels | 2,000 | $12,000 | 40kW |
| 7. Charge Controllers | 100 | $2,000 | 3 Strings |
| 8. Batteries (LiFePO4) | 800 | $15,000 | 100kWh |
| 9. Inverters | 150 | $3,000 | 3x Multiplus |
| 10. Water Makers | 300 | $8,000 | 2x 40gph |
| 11. AC | 400 | $4,000 | 4x Window units |
| 12. Insulation | 500 | $3,000 | Foam |
| 13. Finish (Floor/Cab/Bath) | 3,000 | $25,000 | Marine grade |
| 14. Waste Tanks | 200 | $1,500 | Poly |
| 15. Glass/Doors | 400 | $5,000 | Sliding doors |
| 16. Fridge | 100 | $1,500 | Residential |
| 17. Biofouling (Year 1) | 1,000 | $0 | Growth weight |
| 18. Safety Equip | 300 | $2,500 | Life vests, rafts |
| 19. Dinghy | 200 | $3,000 | Inflatable |
| 20. Sea Anchors | 200 | $1,500 | Parachute |
| 21. Kites | 50 | $1,000 | 20x Kites |
| 22. Air Bags (32 total) | 300 | $3,000 | Backup flotation |
| 23. Starlink | 20 | $1,500 | 2x Units |
| 24. Trash Compactor | 50 | $800 | Marine |
| 25. Misc/Fitting | 1,000 | $5,000 | Bolts, rails, etc |
With 3.9ft diameter legs, the waterline area is small. However, the "pitch" (rocking front to back) depends on the length of the platform (50ft) vs wave length.
| Wave Height | Estimated Tip (Front to Back) | Comfort Level |
|---|---|---|
| 3 ft | ~0.5 ft | Comfortable |
| 5 ft | ~1.5 ft | Moderate motion |
| 7 ft | ~3.0 ft | Significant motion (stomach upset) |
Note: Because of the heavy displacement and deep "keel" (legs), this platform will likely pitch less than a 100ft catamaran in the same waves. Catamarans have high centers of gravity and narrow hulls.
The righting moment (stability) is provided by the deep legs acting like a keel. The overturning force is wind on the pyramid living space.
You cannot stay on board. You must either:
Given the massive steel/aluminum structure and legs, a fiberglass yacht hitting it would suffer catastrophic damage (like hitting a concrete breakwater). The Seastead would likely be unscathed, maybe scratched paint.
Interior Sq Ft of Seastead: Base 1,080 sq ft * 2.5 floors (usable) = ~2,500 sq ft.
Comparable Catamaran: A 50-60 foot catamaran (like a Lagoon 560) has roughly 2,000-2,500 sq ft of living space.
Cost: Used Lagoon 560 is ~$1.5M. New is ~$2M+.
Cost Ratio: The Seastead is ~10x cheaper ($150k vs $1.5M).
Motion: Yes, the Seastead will pitch/roll significantly less in 7ft waves due to the deep, dampening leg effect compared to a lightweight catamaran.
$1,000/day. Cost $150k.
150 days (approx 21-22 weeks) of full occupancy to pay for the first unit.
Cost per sq ft of Seastead: $150,000 / 2,500 sq ft = $60/sq ft.
Viable Niche: Yes. The $60/sq ft is the hook. It offers ocean living accessible to the upper-middle class or as a unique rental property. It solves the "not in US waters" issue for those wanting tax/legal freedom.