With three cylindrical legs (3.9 ft diameter, 16 ft submerged):
| Parameter | Duplex 2205 Stainless | Marine Aluminum (5083) |
|---|---|---|
| Wall Thickness | 1/4" sides, 1/2" ends | 3/8" sides*, 3/4" ends* |
| Weight (3 legs) | 10,400 lbs (4,730 kg) | 5,300 lbs (2,400 kg) |
| Material Cost | $45,000-$60,000 | $24,000-$30,000 |
| Life Expectancy | 25-30 years (excellent corrosion resistance) | 15-20 years (requires anodes/paint) |
| Fabrication | Difficult, requires specialized welding | Easier to fabricate and repair |
*Recommended reduction from 1/2" to 3/8" to save 1,800 lbs critical weight.
With 24 ft legs at 45° from 50 ft triangle corners:
The legs are short and stocky (L/D = 6.15), making them resistant to Euler buckling. With the tensegrity cables providing lateral support at the bottom and the ball joint at top, the critical buckling load exceeds 1,000 metric tons axial.
Lateral load capacity: The structure can withstand current speeds up to 8-10 knots sideways before yielding (well above typical ocean currents).
Available thrust: 4 × 2,090N = 8,360N (1,880 lbs)
| Wind Speed | Drag Force | Power to Hold Station | Status |
|---|---|---|---|
| 30 MPH | 860 lbs (3,830N) | 51 kW | ✓ Can hold |
| 40 MPH | 1,530 lbs (6,800N) | 122 kW | ⚠ Marginal |
| 50 MPH | 2,380 lbs (10,600N) | 237 kW | ✗ Will drift |
At 1 MPH (0.447 m/s) cruise: Drag is low, maybe 2,000N total. Power = 894W. The 3kW mixers are overkill for cruising but necessary for station-keeping in wind.
For 2 days autonomy: 400 kWh
Three isolated 10kW systems with breaker ties provides excellent redundancy. If one system fails, the other two can handle essential loads (navigation, communications, one AC unit).
| Item | Weight (lbs) | Cost Unit 1 | Cost (20 units) |
|---|---|---|---|
| 1. Legs (Al 5083, 3/8") | 5,300 | $30,000 | $22,000 |
| 2. Body (Al frame + panels) | 8,000 | $180,000 | $120,000 |
| 3. Tensegrity Cables (Dyneema) | 800 | $25,000 | $18,000 |
| 4. Motors & Controllers (4+1) | 1,200 | $40,000 | $32,000 |
| 5. Propellers | 0 | Included | Included |
| 6. Solar Panels (33kW) | 2,200 | $25,000 | $18,000 |
| 7. Charge Controllers (3×10kW) | 150 | $15,000 | $12,000 |
| 8. Batteries (400kWh LiFePO4) | 8,000 | $130,000 | $100,000 |
| 9. Inverters (3×10kW) | 300 | $12,000 | $9,000 |
| 10. Water Makers (2) & Storage | 600 | $13,000 | $10,000 |
| 11. Air Conditioning (4 units) | 800 | $12,000 | $9,000 |
| 12. Insulation | 1,500 | $10,000 | $7,000 |
| 13. Interior (floors, cabinets, furniture) | 4,000 | $50,000 | $35,000 |
| 14. Waste Tanks | 400 | $5,000 | $3,500 |
| 15. Glass & Doors | 1,000 | $15,000 | $12,000 |
| 16. Refrigeration | 200 | $2,000 | $1,600 |
| 17. Biofouling (1st year) | 150 | $0 | $0 |
| 18. Safety Equipment | 500 | $10,000 | $8,000 |
| 19. Dinghy | 300 | $5,000 | $4,000 |
| 20. Sea Anchors (2) | 100 | $4,000 | $3,000 |
| 21. Kite Propulsion | 200 | $10,000 | $8,000 |
| 22. Air Bags (32 total) | 400 | $6,400 | $5,000 |
| 23. Starlink (2 units) | 50 | $4,000 | $3,000 |
| 24. Trash Compactor | 100 | $1,000 | $800 |
| 25. Misc/Contingency (10%) | - | $70,000 | $50,000 |
| TOTALS | ~42,000 lbs (19,000 kg) |
$770,000 | $550,000 |
With the small waterplane area (3.33 m² total) and wide leg spacing (50 ft triangle):
This is significantly more stable than a 100 ft catamaran, which would experience 10-15° rolls in 7 ft seas.
With the pyramid body (low center of gravity with batteries at corners) and 50 ft beam:
Bad Cases to Worry About:
Weather Routing: With 5-7 day forecasts, you have adequate warning to reach open ocean 300+ miles from hazards. The seastead can drift 100 miles during a storm and still be safe.
Against fiberglass yachts: The duplex or aluminum legs with 3/8" walls will likely slice through or crush fiberglass hulls with minimal damage to the seastead (perhaps paint/deep scratches). The seastead is the "heavy ship" in collisions. Risk is to the yacht, not the seastead.
| Location/Type | Cost per sq ft | Notes |
|---|---|---|
| This Seastead | $335 | 2,300 sq ft / $770k |
| Nantucket Beach House | $2,000-$4,000 | Land value dominant |
| Malibu Oceanfront | $1,500-$3,000 | High construction costs |
| 100 ft Catamaran (comparable space) | $870-$1,300 | $2M-$3M for 2,300 sq ft |
Catamaran Comparison: A 90-100 ft catamaran offers comparable interior space (2,000-2,500 sq ft) but costs $2.5M-$4M. The seastead is 3 to 5 times cheaper and has superior stability in 7 ft seas (6° vs 15° roll).
Rating: High Viability. The cost per square foot ($335) is competitive with luxury houseboats and vastly superior to oceanfront real estate. The "gentle motion" value proposition in 7 ft seas is unique. Target market: Luxury eco-tourism, digital nomad retreats, research stations.