All values are order‑of‑magnitude estimates based on the description provided. They are intended to give a realistic “ball‑park” figure for a prototype‑level design.
| Parameter | Value | Units |
|---|---|---|
| Wing‑shaped spar dimensions (chord × thickness × span) | 10 ft × 5 ft × 39 ft | ft |
| Cross‑sectional area (ellipse) | π × 5 × 2.5 = 39.3 | ft² |
| Under‑water height (70 % of 39 ft) | 27.3 | ft |
| Under‑water volume | 39.3 × 27.3 ≈ 1 072 | ft³ |
| Water density (seawater) | 64.2 | lb/ft³ |
| Displacement | ≈ 68 800 | lb |
| Component | Estimated weight (lb) | Notes |
|---|---|---|
| Duplex‑SS hull shell (≈1 050 ft², 6 mm thick) | ≈ 10 300 | Vol ≈ 20.7 ft³ × 500 lb/ft³ |
| Internal floors (5 floors, steel grating & frames) | ≈ 5 000 | ≈ 1 000 lb per floor |
| Porch platform (20 ft × 20 ft, 0.05 ft thick) | ≈ 10 000 | Plate + supports/railing ≈ 3 000 lb |
| Solar panels (720 ft², ≈ 2 lb/ft²) | ≈ 1 440 | 400 ft² roof + 320 ft² fold‑out |
| Battery bank (see §4) | ≈ 3 600 | Li‑FePO₄, 20 lb/kWh |
| Inverters, control electronics, misc. | ≈ 1 500 | |
| Cable, winch, rotating fairings | ≈ 500 | |
| Sub‑total (structure + equipment) | ≈ 32 340 | |
| Ballast (steel/concrete) | ≈ 12 000 | Low‑CG weight to achieve stable trim |
| Total weight (approx.) | ≈ 44 340 |
Displacement ≈ 68 800 lb, giving a buoyancy margin of ≈ 24 000 lb – enough for payload (people, stores, water, extra equipment).
| Item | Value |
|---|---|
| Porch roof | 20 ft × 20 ft = 400 ft² |
| Fold‑out side panels (2 × 20 ft × 8 ft) | 320 ft² |
| Total panel area | ≈ 720 ft² |
| Average Caribbean insolation | ≈ 5.5 peak‑sun‑h/day |
| Panel performance (typical 15 W/ft² × 5.5 h) | ≈ 0.0825 kWh/ft²/day |
| Gross daily energy | ≈ 59 kWh |
| System losses (inverter, charger, wiring) – ~20 % | ≈ 12 kWh loss |
| Usable daily energy | ≈ 45–50 kWh |
| Parameter | Value |
|---|---|
| Daily usable energy (chosen for calcs) | 45 kWh |
| 4‑day storage | 180 kWh |
| Specific weight (LiFePO₄ incl. packaging) | ≈ 20 lb/kWh |
| Battery weight | ≈ 3 600 lb |
| Parameter | Value |
|---|---|
| Usable daily energy | 45 kWh |
| Average power (over 24 h) | 45 kWh / 24 h ≈ 1.875 kW (1 875 W) |
| Power allocated to propulsion (60 %) | 0.6 × 1.875 ≈ 1.125 kW (1 125 W) |
| Number of RIM‑drive thrusters | 8 |
| Average power per thruster | ≈ 140 W |
The 140 W average per thruster is modest. In practice the thrusters can be over‑driven for short bursts (e.g., 2–3 × average) using stored battery energy, giving short‑term thrust of a few hundred watts per unit.
Using a propulsive efficiency of ~50 % (typical for small electric thrusters) and a drag coefficient for a slender spar (Cd ≈ 0.2), the thrust needed to overcome drag at low speed is roughly:
The 8 thrusters can deliver ≈ 20–30 lbf of thrust per kilowatt of electrical input. With an average of 1.125 kW to the thrusters the net thrust is roughly 25–35 lbf – enough to overcome drag at about 1 mph. When the thrusters are run at higher bursts (up to ~3 kW total for short periods) the thrust can reach ~80 lbf, pushing the platform to perhaps 1.5–2 mph in calm water. In a seaway the speed will be lower, typically 1–2 mph.
| Control method | Expected effectiveness |
|---|---|
| Differential thrust (higher vs. lower thrusters) – pitch reduction | Limited – thrusters are clustered near the thickest part of the spar, giving a short lever arm. Expect a modest 10‑20 % reduction in pitch amplitude. |
| Turning (yaw) to keep bow into waves – roll reduction | More effective. With a low centre of gravity (ballast) the natural roll period is already long. Active yaw to align with the wave direction can cut roll angles by ~30 %. |
| Overall stability | The deep ballast and long vertical spar give a high righting lever. Even without active control roll angles are expected to stay under 5° in typical Caribbean swell. |
Using deep‑water wave theory (period 6–8 s) and exponential decay with depth, the peak orbital acceleration at the surface is ≈ 0.05 g for a 3‑ft wave, 0.08 g for a 5‑ft wave, and 0.10 g for an 8‑ft wave. At each floor the acceleration is reduced by the depth factor.
| Floor (from bottom upward) | Approx. height above still‑water line (ft) | 3‑ft wave (g) | 5‑ft wave (g) | 8‑ft wave (g) |
|---|---|---|---|---|
| Floor 1 (batteries, deepest) | –20 | ≈ 0.02 | ≈ 0.03 | ≈ 0.04 |
| Floor 2 | –12 | ≈ 0.03 | ≈ 0.05 | ≈ 0.07 |
| Floor 3 | –5 | ≈ 0.04 | ≈ 0.06 | ≈ 0.09 |
| Floor 4 | +2 | ≈ 0.05 | ≈ 0.08 | ≈ 0.11 |
| Floor 5 (just below porch) | +8 | ≈ 0.07 | ≈ 0.10 | ≈ 0.14 |
| Porch (open platform) | +20 | ≈ 0.09 | ≈ 0.13 | ≈ 0.18 |
These values include both vertical orbital acceleration and a modest contribution from roll (≈ 5° max). The total g‑force is well below the discomfort threshold (≈ 0.3 g) for all but the most extreme 8‑ft waves, suggesting the living quarters will be relatively comfortable.
A heavy keel (steel or concrete) of roughly 10 000–15 000 lb provides a low centre of gravity, giving a righting lever that dominates roll dynamics. The cable to the ballast can be 10–20 m (≈ 30–65 ft) long; a longer cable increases the pendulum‑like stabilizing effect but also adds drag and must be tensioned to avoid sagging. A winch is useful for fine‑tuning, but a fixed cable with rotating fairings is simpler and reduces vortex‑induced vibration. We suggest a fixed cable length of about 15 m (≈ 50 ft) with freely rotating fairings.
| Item | Estimated cost (USD) |
|---|---|
| Duplex‑SS hull & porch (material + fab) | $80 000 |
| Solar panel system (≈ 10 kW, incl. mounting) | $5 000 |
| Li‑FePO₄ battery bank (180 kWh) | $40 000 |
| 8 × RIM‑drive thrusters | $16 000 |
| Inverters, controllers, wiring | $5 000 |
| Winch, cable, fairings | $2 000 |
| Basic interior (floors, simple fittings) | $15 000 |
| Logistics, shipping, misc. | $10 000 |
| Total | ≈ $173 000 |
Costs are rough and can vary with supplier, exchange rates, and specification refinements. Volume production would lower the price per unit.
Answer: Yes – the concept is sound. The wing‑shaped spar fits in a standard 40‑ft container, uses readily available duplex stainless, and provides a stable, low‑centre‑of‑gravity platform. The main challenges are:
With those tweaks the design could evolve into a practical, low‑cost “tiny house on the sea” that can be shipped worldwide, assembled on site, and operated with renewable energy.
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