Design Specifications
Spar Dimensions:
39ft × 10ft × 5ft
Material:
Duplex Stainless Steel
Container Compatibility:
Fits in 40ft Container
Underwater Portion:
70% (≈27.3ft)
Floors Inside Spar:
5 Levels
Porch Area:
20ft × 20ft
Thrusters:
8 RIM-drive units
Weight & Buoyancy Analysis
Structural Weight Estimates
Spar Structure (Duplex Steel):
≈15,000 lbs
Porch Structure:
≈3,500 lbs
Ballast Cable & Fairings:
≈800 lbs
Interior (Basic):
≈4,000 lbs
Systems & Equipment:
≈2,500 lbs
Total Structural Weight:
≈25,800 lbs
Displacement & Payload
Spar Volume (approx):
1,950 ft³
Seawater Weight (64 lb/ft³):
124,800 lbs
Net Buoyancy (Structure subtracted):
≈99,000 lbs
Available for Ballast & Payload:
≈73,200 lbs
Power System Analysis
Solar Power Generation
Fixed Solar Area (20×20ft):
400 ft² (37.2 m²)
Expandable Solar Panels:
+ 640 ft² (59.5 m²)
Total Solar Area (deployed):
1,040 ft² (96.6 m²)
Panel Efficiency:
22% (modern panels)
Caribbean Solar Insolation:
5.5 kWh/m²/day avg
Estimated Daily Generation:
≈53 kWh/day (deployed)
Estimated Daily Generation (folded):
≈20 kWh/day
Battery Storage
4 Days Storage at 53 kWh/day:
212 kWh capacity
Lithium Battery Weight (est.):
≈2,650 lbs (12.5 lb/kWh)
Average Available Power (24h):
≈2,208 W continuously
Ballast & Stability
Ballast Recommendations
For optimal stability in Caribbean waves (3-8 ft):
Recommended Ballast Weight:
15,000 - root.25,000 lbs
Cable Length:
50-80 ft below spar
Cable System Recommendation: Winch system preferred over fixed cable. This allows:
- Adjustment for different sea states
- Ability to raise ballast for maintenance
- Optimization for travel vs. stationary operation
- Emergency ballast release capability
Stability Analysis
The wing-shaped spar design should provide:
- Natural pitch resistance: Wing shape provides hydrodynamic damping
- Roll reduction: Deep ballast + low CG + active thrusters
- Wave alignment: Ability to turn into waves reduces cross-sectional area
Mobility & Performance
Thruster Performance
Available Power for Thrusters:
1,325 W (60% of avg)
RIM-drive Efficiency:
≈70% power to thrust
Total Thrust Power:
≈928 W effective
Speed Estimate
For a wing-shaped spar with 8 RIM-drive thrusters:
Estimated Cruising Speed:
3.5 - 4.5 MPH (3.
0 - 4.0 knots)
This assumes calm conditions. Speed would decrease in waves or adverse currents.
Motion Control Effectiveness
Pitch Reduction (thrusters):
Moderate (20-30% reduction)
Roll Reduction (turning):
Significant (40-50% reduction)
The differential thrust capability will be most effective against roll when proactively turning into waves.
Comfort & Habitability
Estimated Motion by Floor Level
Floor 1 (Bottom):
Minimal motion, < 0.1g in 8ft waves
Floor 2 (Lowest acceleration):
Very comfortable, < 0.15g
Floor 3 (Mid-level):
Moderate motion, ≈0.2-0.25g
Floor 4 (Upper):
Noticeable motion, ≈0.3g
Floor 5 (Top of spar):
Significant motion, ≈0.4g
Porch Area (Above spar):
Most motion, ≈0.5g in 8ft waves
Wave Conditions
- 3ft waves: All levels comfortable, porch usable most times
- 5ft waves: Lower 3 floors comfortable, upper floors noticeable, porch limited use
- 8ft waves: Bottom 2 floors comfortable, upper floors challenging, porch unusable
Cost Estimate
Fabrication in China (Basic Interior)
Duplex Steel Spar Fabrication:
$85,000 - $120,000
Porch Structure & Components:
$25,000 - $35,000
8 RIM-drive Thrusters:
$40,000 - $60,000
Solar System (1+ kW):
$15,000 - $25,000
Battery System (212 kWh):
$30,000 - $45,000
Ballast & Winch System:
$8,000 - $15,000
Basic Interior Fit-out:
$20,000 - $30,000
Total Estimated Cost:
$223,000 - $330,000
Note: Does not include design, engineering, shipping, or assembly costs.