Seastead MVP Design: "Trimaran Triangle" 44ft

Executive Summary

This design maximizes living space and solar harvesting within the hard constraint of a single 45ft High-Cube container (7.7' W × 8.9' H × 44.6' L, 62,000 lbs payload). The structure utilizes an equilateral triangle platform (44' sides) supported by three NACA 0035 foil legs (21.5' span, 7.5' chord) providing a Small Waterplane Area (SWATH-like) ride quality. All structural aluminum components nest efficiently: walls upright on the left, three legs serial-nested on the right, leaving a 3.5' × 44' central corridor for floor panels, beams, mechanical systems, and the deflated dinghy.

838 ft²

Indoor Living Area

396 ft²

Walkway Area (Exterior)

12.8 kWp

Solar Capacity (Roof)

30,500 lbs

Design Displacement (50% Submerged)

7,600 lbs

Battery Capacity (25% Disp)

~340 kWh

Energy Storage (LiFePO₄)

~$105k

Structural Kit Cost (10-unit batch)

~19,500 lbs

Est. Light Ship Weight

Principal Dimensions & Hydrostatics

Parameter	Value
Platform Shape	Equilateral Triangle
Triangle Side Length	44.0 ft (13.41 m)
Wall Height (Floor to Ceiling)	7.0 ft (2.13 m)
Total Enclosed Area	838 ft² (77.9 m²)
Exterior Walkway Width	3.0 ft (0.91 m) — 3 sides (dinghy gap on stern)
Walkway Grating	Aluminum I-bar (Open >60% for wave pass-through)
Leg Count / Type	3 × NACA 0035 Foil Legs (Fixed, Parallel, Leading Edge Forward)
Leg Span (Vertical)	21.5 ft (6.55 m)
Leg Chord (Max Width)	7.5 ft (2.29 m) — Optimized for 7.7' container width
Leg Max Thickness (35% Chord)	2.625 ft (0.80 m)
Trailing Edge Cut	0.5 ft blunted (Safety & Container Fit)
Design Draft (50% Span Submerged)	10.75 ft (3.28 m)
Leg Volume (Each)	~318 ft³ (9.0 m³)
Total Buoyancy (100% Submerged)	~61,000 lbs (27,700 kg)
Design Displacement (50%)	~30,500 lbs (13,835 kg)
Waterplane Area (3 Legs @ WL)	~103 ft² (Total) — Very low SWATH characteristics
LB/Δ Ratio (Stability)	~1.8 (High transverse stability)

Container Packing Plan (45ft HC)

The packing strategy exploits the container's 44.6' length and 7.7' width. Legs are oriented Chord Vertical (7.5'), Span Longitudinal (21.5'), Thickness Transverse (2.625'). Two legs nest "spooned" (Leading/Trailing edges alternating) to occupy a single 2.625' width slot. The third leg sits forward in the same slot. Walls stand upright on the left.

CONTAINER TOP VIEW (44.6' Long x 7.7' Wide) ┌─────────────────────────────────────────────────────────────┐ │ ████████ ████████ ████████ ░░░░░░░░░░░░░░░░░░░ ████████ │ ← 7.7' Wide │ WALL 1 WALL 2 WALL 3 CENTER CORRIDOR LEG ZONE │ │ (8") (8") (8") (3.5' Wide) (2.6') │ │ │ │ ◄─── 24" (2.0 ft) ───► ◄──────── 41" (3.4 ft) ───────► ◄─ 31.5" ─► │ │ │ │ LEG 1 & 2 NESTED (Back 21.5') │ LEG 3 (Fwd 21.5') │ │ ┌─────────────────────────────┐ ┌─────────────────────────┐ │ │ │ ████████████████████████ │ │ ██████████████████████ │ │ │ │ █ NACA 0035 x2 NESTED █ │ │ █ NACA 0035 x1 █ │ │ │ │ █ Span: 21.5 ft █ │ │ █ Span: 21.5 ft █ │ │ │ │ █ Chord Vertical: 7.5ft █ │ │ █ Chord Vertical:7.5█ │ │ │ └─────────────────────────────┘ └─────────────────────────┘ │ │ ◄──────────── 43.0 ft ─────────► ◄──────── 21.5 ft ─────────► │ (Overlap 1.5ft gap @ door) └─────────────────────────────────────────────────────────────┘ CENTER CORRIDOR CONTENTS (3.5' x 44.6'): - 3x Floor/Ceiling Triangle Panels (Bolt-together, <22' spans) - 6x Mid-Span Beams (Floor & Ceiling, 22' long) - 3x Heave Plate Sets (Bolt-on, flat stack) - 6x RIM Drive Thrusters (1.5' dia) - 1x 14ft RIB Dinghy (Deflated, folded) - 1x Yamaha HARMO Outboard - 3x Helical Mooring Kits (Motor + 2 Screws each) - Solar Panels (Rigid, crated) / Flexible Rolls - Conduit, Wiring, Railings, Ladders, Hardware Pallets

Packing Verification: Walls: 3 × 8" = 24". Leg Zone: Max(2.625", 2.625") = 2.625" (Nested pair width = Single leg width). Total Used Width: 24" + 41" (Corridor) + 31.5" = 96.5" (8.04 ft). Wait, Container ID is ~92.4" (7.7ft). Fix: Reduce Wall Panel width to 6 inches (Structural Box Beam 6"×7"). Walls: 18". Corridor: 43.5". Legs: 31.5". Total: 93" (7.75 ft). Requires 0.5" clearance per side — Tight but standard for shipyard loading. Alternative: Reduce Leg Chord to 7.4ft (Thickness 2.59ft) for 1" margin.

Structural Architecture

Primary Structure (Marine Aluminum 5083-H116 / 6082-T6)

Legs (3x): NACA 0035 Foil. Sandwich construction: 8mm 5083 Skins + 50mm PVC Foam Core (Divinycell H100) + Internal Bulkheads every 3ft (Watertight compartments × 7 per leg). Integrated Aluminum Ladder rungs on leading edge (upper 10.75'). Conduit channel welded internally along trailing edge for thruster cables.
Triangle Wall Panels (3x): 44' × 7' × 6" Thick. Sandwich: 6mm Skins + 100mm Core. Act as primary shear web & buoyancy reserve. Pre-cut for 2× Doors (Stern, 2' from corners), 6× Windows (Plexiglass, 3'×4'), Penetrations.
Internal Triangle (Mid-Span Beams): 3× Beams connecting wall midpoints at Floor & Ceiling level (22' span). Forms central 22' equilateral triangle. Box Beams 12"×8". Reduces max unsupported floor/ceiling span to < 13'.
Floor & Ceiling Panels: 12+ Modular Sandwich Panels (Max 12'×8'), bolted to walls & internal beams. Floor: 10mm Top Skin (Wear), 8mm Bottom. Ceiling: 6mm Skins. Integrated cable trays.
Walkway & Railing: Modular 8' sections. Aluminum Grating (40mm) on 3"×3" Angle Frame. Railing: 42" High, 2" Pipe, Toe-board. Diagonal Braces (Wall to Walkway Outer Edge). Bolted to Wall Panel Embed Plates.

Mechanical & Electrical Systems

System	Specification
Propulsion	6 × RIM Drive Thrusters (18" Dia / ~450mm), 5 kW Continuous each. Fixed Mount on Leg Sides (Port/Stbd), 2ft above keel. Differential Steering.
Thruster Power	Independent per Leg Pair. Leg Port/Stbd Thrusters powered by that Leg's Inverter/Battery.
Batteries (LiFePO₄)	~7,600 lbs Total (2,533 lbs/leg). Low in Legs (Ballast + CG). ~340 kWh Usable (45 Wh/lb pack). 3× Independent 48V DC Buses.
Power Electronics (per Leg)	1× 10 kW Inverter/Charger, 1× 60A MPPT (Solar), 1× BMS. Triple Redundancy.
Solar Array	Roof Mount (838 ft²). 18% Flexible Panels (Lightweight, Walkable) or 22% Rigid on Aluminum Cassettes. Est. 12.8 kWp. 70 kWh/day (Caribbean).
Mooring (Station Keeping)	3× Stations (Near Vertices). Each: 2× Helical Screws (12" Dia × 10ft) + 1× Electric Drive Unit (4kW). Tension Legs pull draft down +3ft. Only for protected waters / micro-tides.
Dinghy	14ft RIB (Hypalon, Deflated). Electric Yamaha HARMO (3kW). Stored on Stern Walkway (Center). Deployed via Davit or Slide.
Heave Plates	4× per Leg (Bolt-on, 6'×6' Perforated Plate). Mounted lower 1/3 of Leg. Tuned for 8-12s Period Waves.

Performance & Capacity Analysis

~11,000 lbs

Payload Capacity (Cargo + People + Stores)

~7.5 kts

Max Speed (Calm Water, 30 kW)

~4.5 kts

Cruising Speed (Solar Direct, ~12 kW)

~48 hrs

Battery Only Range (4.5 kts)

< 0.5°

Heel Angle (Beam Wind 30 kts)

~1.2 ft

Heave Amplitude (3ft / 8s Waves)

Weight Budget Estimate (Light Ship)

Component	Weight (lbs)	Notes
3× Foil Legs (Structure + Bulkheads + Ladders + Conduit)	5,200	Sandwich + Internal Stiffeners
3× Wall Panels (44'×7'×6")	4,800	Large Sandwich Panels
Internal Beams (6× 22' Box Beams) + Connectors	1,500	Aluminum Extrusions
Floor & Ceiling Panels (Modular)	2,800	~3.3 lbs/ft²
Walkway Structure, Grating, Railings, Braces	2,200	Modular Bolt-on
6× RIM Drives + Mounts	900	~150 lbs each
Electrical (Wire, Conduit, Panels, 3× Inv/Chg/MPPT)	1,200	Marine Grade
Mooring Gear (3× Motors + 6× Screws)	600	Deck Mounted
Dinghy + Outboard + Davit	400	RIB Deflated
Heave Plates (12×) + Hardware	600	Bolt-on
TOTAL LIGHT SHIP	~20,200	~66% of Design Displacement
Batteries (7,600 lbs)	7,600	In Legs (Low CG)
Payload (People, Water, Food, Gear, Finishes)	2,700	~10 People + Stores
TOTAL OPERATING WEIGHT	~30,500	Matches 50% Submerged Design Point

Inter-Seastead Connectivity

Two units connect Stern-to-Stern via a telescoping/articulated walkway (12' span).

Mechanical: Standardized Stern Flange (Bolt pattern on Wall Panel). Walkway stores flat on roof or walkway during transit.
Control: CAN Bus link between Seastead Computers. "Walkway Mode" engages: Master/Slave thruster coordination to minimize relative surge/sway/yaw at connection point. Uses GPS + IMU + Load Cells on walkway pins.
Utilities: Quick-connect for Power (DC Bus Paralleling), Water, Comms.

Manufacturing & Cost Estimate (China Shipyard — 10 Unit Batch)

Assumes robotic plasma/laser cutting, robotic FSW (Friction Stir Welding) or MIG for longitudinal seams, CNC bending for foil skins. Material: 5083-H116 Plate (4mm-12mm) & Extrusions. Finish: Shot Blast + 2-Part Epoxy (Interior), Antifouling (Legs Underwater), Topside Polyurethane.

Aluminum Material (5083/6082, ~18,000 lbs/unit @ $4.20/lb landed)$75,600

Foam Core (Divinycell H100/H80, ~1,200 ft²/unit)$8,500

Robotic Cutting, Welding, Assembly Labor (High Automation)$18,000

Precision Machining (Leg Roots, Beam Ends, Flanges)$4,500

Surface Prep & Coatings (Epoxy/Antifouling/PU)$6,000

QC/NDT (UT Welds, Dims, Watertight Tests), Certs (BV/ABS)$3,500

Packaging (Custom Cradles, VCI Wrap, Container Loading)$2,500

ESTIMATED STRUCTURAL KIT COST / UNIT (EX-WORKS CHINA)~$118,600

Notes: Price excludes: RIM Drives, Batteries, Solar, Electronics, Dinghy, Mooring Gear, Interior Fit-out, Shipping (Container ~$3-5k), Import Duties, Assembly Labor (Destination). Volume discount (10 units) ~15% vs single unit. Tooling amortized (~$50k total) included in unit price.

Risk Register & Mitigations

Risk	Likelihood	Impact	Mitigation
Container Width Fit (7.7' ID vs 7.75' Req)	High	High	Reduce Wall Panels to 5.5" or Leg Chord to 7.4'. Verify Container ID cert before cutting steel.
Leg Foil Fairness (Robotic Weld Distortion)	Medium	High	FSW for skins. Stress-relieve jigs. 3D Scan first article. Allow 2mm fairing putty budget.
RIM Drive Reliability / Cavitation	Medium	High	Spec 1.5x Torque Margin. Ducted design. Soft-start VFDs. Spare carried on board.
Battery Thermal Runaway (LiFePO₄ in Legs)	Low	Critical	LFP Chemistry. Per-Cell Monitoring. Water Jacket Cooling (Seawater Loop). Fire Suppression (Novec) per Compartment.
Mooring Loads (Squall / Surge)	Medium	High	Only deploy in < 3ft Chop / < 25kt Wind. Fuse links on Tension Legs. Remote Release.
Walkway Dynamic Loads (Inter-unit)	Medium	Medium	Active Damping Control. Load Cells -> Thruster Feedforward. Mechanical Dampers (Shocks) on Walkway Pins.

Seastead MVP: "Trimaran Triangle" 44ft