The equilateral triangle roof (44 ft sides) provides approximately 838 sq ft of area. Assuming 70% usable solar area (accounting for edges, walkways, and equipment) yields ~586 sq ft. At ~15 Watts/sq ft for modern rigid panels, we get:
Battery Specifications:
Average Continuous Power:
48.4 kWh / 24 hrs = 2,016 Watts available continuously if drawn evenly over 24 hours.
When pointing into the wind, the frontal area is roughly 300 sq ft (Legs: ~148 sq ft, Cabin: ~154 sq ft). Using standard aerodynamic drag formulas ($F = 0.5 \times \rho \times V^2 \times C_d \times A$, with $C_d \approx 1.2$ and propulsion efficiency ~50%):
| Wind Speed (MPH) | Drag Force (lbs) | Mechanical Power to Hold | Electrical Power Needed (Watts) |
|---|---|---|---|
| 20 MPH | ~367 lbs | ~14.5 kW | ~29 kW |
| 30 MPH | ~828 lbs | ~49 kW | ~98 kW |
| 40 MPH | ~1,472 lbs | ~116 kW | ~232 kW |
| 50 MPH | ~2,300 lbs | ~227 kW | ~454 kW |
Note: At 40+ MPH, the 230kWh battery would be drained in about an hour. Station-keeping in high winds is not sustainable purely on batteries.
By aiming across the wind, the NACA 0040 legs act as keels. The submerged lateral area is ~185 sq ft. The NACA 0040 will stall at an angle of attack of about 10-12 degrees, generating a $C_L$ of ~1.0. Because the seastead has high windage and limited keel aspect ratio, it can likely maintain control (without excessive leeway) in winds up to 30-35 MPH. Beyond this, the foils will stall, leeway will increase dramatically, and control will become marginal despite differential thrust.
Running downwind at 20 degrees off with differential thrust presents a severe broaching risk. The flat back of the cabin acts as a sail, pushing the stern around. The blunt leading edges of the NACA foils track well, but if the stern swings too far, the wind catches the broadside. With thrusters fighting this, you could maintain control up to about 45-50 MPH winds. Beyond this, the risk of a "death roll" or uncontrollable broach is too high. You cannot outrun a storm at 5 MPH.
| System | Average Draw (Watts) |
|---|---|
| Refrigeration | 150 |
| Watermakers (2hrs/day) | 100 |
| Starlink (2 units) | 120 |
| Electronics/Lighting/Ventilation | 200 |
| Incinerating Toilet (intermittent) | 50 |
| Misc / Pump cycles | 80 |
| Total Average House Load | ~700 Watts |
With 1,316 Watts of continuous excess power, the propulsive thrust will overcome the low drag of the NACA 0040 foils at low speeds. At ~1.3 kW of electrical power, you can maintain approximately 2.5 to 3 MPH (2.1 to 2.6 knots) 24/7 purely on sunlight.
| Item | Weight (lbs) | Cost (USD) |
|---|---|---|
| 1) 3x Legs (Marine Aluminum, bulkheads) | 3,000 | $15,000 |
| 2) Body (Frame, walls, roof, beams) | 5,500 | $30,000 |
| 4) 6x RIM Drive Thrusters | 600 | $18,000 |
| 6) Solar Panels (8.8kW) | 600 | $6,000 |
| 7) Solar Charge Controllers (3x) | 90 | $3,000 |
| 8) Batteries (230 kWh LiFePO4) | 6,900 | $20,700 |
| 9) Inverters (3x 5kW) | 150 | $6,000 |
| 10) 2x Water Makers + Storage (100gal) | 350 | $8,000 |
| 11) AC Units (3x 12k BTU) | 300 | $5,000 |
| 12) Insulation (Closed-cell spray foam) | 400 | $4,000 |
| 13) Flooring, cabinets, kitchen, bath, bed | 2,000 | $15,000 |
| 14) Waste Tanks (2x 50gal) | 100 | $1,500 |
| 15) Glass & Glass doors (Marine grade) | 600 | $6,000 |
| 16) Refrigerator (12V Marine) | 100 | $1,500 |
| 17) Davit/Crane for Dinghy | 250 | $4,000 |
| 18) Safety Equipment (EPIRB, raft, jackets, flares) | 200 | $5,000 |
| 19) Dinghy + Yamaha HARMO | 500 | $15,000 |
| 20) 2x Sea Anchors + Rode | 100 | $2,000 |
| 21) Kite Array (20x 6ft kites + lines) | 100 | $10,000 |
| 22) 24x Air Bags (inflatable buoyancy) | 150 | $2,000 |
| 23) 2x Starlink Kits | 30 | $2,500 |
| 24) Trash Compactor | 80 | $1,000 |
| 25) 3x Heave Plates (20 sq-ft each) | 600 | $3,000 |
| 26) Electric Incinerating Toilet | 50 | $2,000 |
| 27) Misc (Wiring, plumbing, anodes, paint, hardware) | 1,000 | $10,000 |
| TOTALS | ~23,650 lbs | $196,200 |
This design is effectively a SWATH (Small Waterplane Area Twin/Tri Hull). The waterplane area is very small (~369 sq ft total) but the stance is wide (25 ft from center to float). This creates a very high Metacentric Height (GM), making the vessel extremely stiff.
Because of the small waterplane area, the seastead will largely "ignore" wave heights, mostly maintaining its level. However, the submerged foils will experience orbital wave velocities, causing dynamic lift/drag forces.
| Wave (H/Period) | Speed | Front Wave Tip (ft) | Side Wave Tip (ft) | G-Force at Center (Front) | G-Force at Center (Side) |
|---|---|---|---|---|---|
| 3ft / 3s | 4 kts | 0.3 ft | 0.4 ft | 0.04 G | 0.05 G |
| 3ft / 3s | 5 kts | 0.4 ft | 0.5 ft | 0.05 G | 0.06 G |
| 5ft / 5s | 4 kts | 0.8 ft | 1.0 ft | 0.06 G | 0.08 G |
| 5ft / 5s | 5 kts | 1.0 ft | 1.2 ft | 0.08 G | 0.10 G |
| 7ft / 7s | 4 kts | 1.5 ft | 1.8 ft | 0.08 G | 0.11 G |
| 7ft / 7s | 5 kts | 1.8 ft | 2.2 ft | 0.10 G | 0.14 G |
Note: These are estimates. The 3-second period waves are close to the vessel's natural roll period, which could induce resonance without the heave plates. The G-forces are low but rapid, feeling like a quick vibration or jolt rather than a slow roll.
Battery Only (No Solar, Cloudy):
Assuming ~2kW draw for house loads + propulsion draw. Usable battery = 80% = 184 kWh.
Battery + Solar (Typical Caribbean Day):
Adding 48.4 kWh over a 12-hour sun period gives an extra ~4 kW continuous during the day.
Into 20 MPH Wind:
Aerodynamic drag roughly triples the power required for propulsion. Range drops by ~60% from the above figures.
Yes, you can register this as a "Trimaran Yacht." Panama, Liberia, and the Marshall Islands are very accommodating to novel designs under 24 meters (79 ft). Since your design is technically a trimaran (3 hulls), fits standard container dimensions, and has no commercial passengers, you can easily register it as a Private Yacht. You will need a naval architect to sign off on stability tests, but as a Yacht, the regulations are vastly more lenient than for commercial vessels.