This is a rough conceptual estimate, not a naval architecture signoff. Because your concept is unusual, some dimensions had to be inferred. The biggest uncertainties are:
Modern marine-installed solar usually lands around 18–22 W/ft² gross panel area depending on module choice. A reasonable planning figure is 20 W/ft².
| Solar Area | Watts per ft² | Installed Watts |
|---|---|---|
| 784 ft² | 18 W/ft² | 14,112 W |
| 784 ft² | 20 W/ft² | 15,680 W |
| 784 ft² | 22 W/ft² | 17,248 W |
Recommended planning value: about 15.7 kW installed solar.
Total displacement at the stated half-submerged condition: about 21,900 lb.
These numbers are very rough but intended to be realistic for welded marine aluminum.
| Component | Rough Weight Estimate |
|---|---|
| 3 large foil floats / legs (welded marine aluminum, stiffened) | 4,500–6,000 lb |
| Main triangle frame / beams / cross structure | 2,000–3,000 lb |
| Living box shell and framing (12 × 28 × 8, many windows) | 3,500–5,000 lb |
| Netting supports, railings, stairs, doors, ladders | 500–1,000 lb |
| Davit/crane structure | 300–700 lb |
| Solar support structure / hinges / fold-out support arms | 600–1,200 lb |
| 6 rim thrusters incl. mounts and cabling | 600–1,200 lb |
Estimated bare structural + propulsion hardware weight: about 12,000 to 18,000 lb.
A reasonable midpoint for planning is ~15,000 lb before batteries, interior fitout, water, crew, RIB, outboard, stores, etc.
| Case | Total Buoyancy @ 50% immersion | Structure Weight | Remaining Capacity |
|---|---|---|---|
| Optimistic | 21,888 lb | 12,000 lb | 9,888 lb |
| Mid estimate | 21,888 lb | 15,000 lb | 6,888 lb |
| Pessimistic | 21,888 lb | 18,000 lb | 3,888 lb |
That remaining capacity must hold:
For one float, each additional foot of immersion adds approximately:
For all 3 legs together: 2,304 lb per additional foot of immersion.
In simple amplitude terms, yes approximately. If wave height is 4 ft crest-to-trough, that is ±2 ft about mean level. If active control removes 1 ft from upward excursion and 1 ft from downward excursion, then apparent motion becomes ±1 ft, or about 2 ft total.
But real comfort depends on:
So it is not exactly “4 ft feels like 2 ft” in all cases, but it is a fair first-order way to think about it.
5 knots = 8.44 ft/s = 2.57 m/s.
To estimate required lift, assume we want one stabilizer on each leg helping vertical control. The amount of force required depends on how quickly the hull is moving vertically in the encountered wave. For a rough conceptual number, assume you need on the order of 500 to 1,500 lb of controllable lift per leg.
Using the lift equation:
L = 0.5 × rho × V² × S × Cl
This gives a needed foil area per stabilizer roughly in the range of:
| Target Lift per Leg | Approx Foil Area at 5 kn |
|---|---|
| 500 lb | ~8–12 ft² |
| 1,000 lb | ~16–24 ft² |
| 1,500 lb | ~24–36 ft² |
Recommended conceptual size: about 20 ft² per stabilizer foil, one on each leg. For example: 5 ft span × 4 ft chord, or 6 ft span × 3.3 ft chord.
That is in the right ballpark to produce meaningful stabilizing force at 5 knots. At 4 knots, much less force is available; at 6 knots, much more.
Assume 3 stabilizer “airplane” assemblies, each with:
| Item | Estimated Cost Each | Estimated Weight Each |
|---|---|---|
| Aluminum foil structure and weldment | $1,200–$2,200 | 90–150 lb |
| Tail/elevator assembly | $300–$700 | 20–40 lb |
| Shaft, bearings, seals, mount | $400–$900 | 20–40 lb |
| Small marine actuator | $400–$1,000 | 10–25 lb |
| Control electronics / sensor / cabling allocation | $300–$800 | 5–15 lb |
Per stabilizer total: $2,600–$5,600, weight 145–270 lb.
Three stabilizers total: $7,800–$16,800, weight 435–810 lb.
A useful planning midpoint is:
Because this is not a standard hull, drag is uncertain. A SWATH-like concept can reduce wave-induced motion but can still have substantial wetted area drag. Your three large immersed foils are relatively thick and deep, which adds wetted area.
For a preliminary estimate including appendage drag and realistic propulsive losses:
| Speed | Estimated Shaft/Electrical Propulsion Power | With Stabilizers Active |
|---|---|---|
| 4 knots | 4–6 kW | 4.5–6.5 kW |
| 5 knots | 7–10 kW | 7.5–11 kW |
| 6 knots | 12–18 kW | 13–19 kW |
For planning, I suggest these midpoint values:
LiFePO4 pack-level specific energy is often about 110–140 Wh/kg depending on packaging. 4,000 lb = 1,814 kg.
Planning value used: 230 kWh nominal, 207 kWh usable (90% usable).
| Speed | Power | Usable Battery | Hours | Range |
|---|---|---|---|---|
| 4 kn | 5 kW | 207 kWh | 41.4 h | 166 nmi |
| 5 kn | 8.5 kW | 207 kWh | 24.4 h | 122 nmi |
| 6 kn | 15 kW | 207 kWh | 13.8 h | 83 nmi |
| Speed | Total Power | Hours | Range |
|---|---|---|---|
| 4 kn | 6 kW | 34.5 h | 138 nmi |
| 5 kn | 9.5 kW | 21.8 h | 109 nmi |
| 6 kn | 16 kW | 12.9 h | 77 nmi |
This is the hardest part to predict without a proper motion model. A realistic answer is that stabilizer effectiveness increases strongly with speed because lift scales with velocity squared.
For a concept-sized foil around 20 ft² per leg:
| Speed | Estimated Crest Reduction | Estimated Trough Reduction | Total Apparent Height Reduction |
|---|---|---|---|
| 4 kn | ~0.3–0.6 ft | ~0.3–0.6 ft | ~0.6–1.2 ft |
| 5 kn | ~0.6–1.0 ft | ~0.6–1.0 ft | ~1.2–2.0 ft |
| 6 kn | ~1.0–1.5 ft | ~1.0–1.5 ft | ~2.0–3.0 ft |
So yes, at about 5 knots, reducing a wave by roughly 1 ft on crest and 1 ft on trough is plausible in favorable conditions. At 6 knots, possibly more. At 4 knots, probably less.
Because of the small waterplane area, actual heave should be much less than wave height, especially for longer-period waves. Still, this depends heavily on wave period and loading.
A rough first-pass estimate for vertical motion at the living platform without active stabilizers:
| Wave Height | 4 kn | 5 kn | 6 kn |
|---|---|---|---|
| 3 ft waves | ~0.7–1.1 ft motion | ~0.8–1.3 ft | ~1.0–1.5 ft |
| 4 ft waves | ~1.0–1.5 ft motion | ~1.2–1.8 ft | ~1.4–2.1 ft |
| 5 ft waves | ~1.3–1.9 ft motion | ~1.5–2.3 ft | ~1.8–2.8 ft |
With active stabilizers:
| Wave Height | 4 kn | 5 kn | 6 kn |
|---|---|---|---|
| 3 ft waves | ~0.5–0.9 ft motion | ~0.4–0.8 ft | ~0.3–0.7 ft |
| 4 ft waves | ~0.8–1.3 ft motion | ~0.6–1.1 ft | ~0.5–1.0 ft |
| 5 ft waves | ~1.1–1.7 ft motion | ~0.9–1.5 ft | ~0.7–1.4 ft |
These are conceptual comfort-motion estimates only, not guaranteed seakeeping values.
For the Caribbean, a good annual-average planning number for fixed horizontal solar is around 5.0 to 5.5 peak sun hours/day. Using 15.7 kW installed:
Using 63 kWh/day average net:
| Usable Battery Capacity | Net Solar per Day | Days to Recharge from Empty |
|---|---|---|
| 207 kWh | 63 kWh/day | ~3.3 days |
Estimated average Caribbean recharge time from empty: about 3 to 4 days.
If average net solar harvest is about 63 kWh/day, that equals:
At that power, steady 24/7 speed would be quite low. Using a cube-law type approximation from the earlier propulsion estimates:
| Condition | Average Propulsion Power Available | Estimated Sustainable 24/7 Speed |
|---|---|---|
| No stabilizers | ~1.63 kW | ~2.6–3.0 kn |
| Stabilizers active | ~1.0–1.3 kW net to propulsion after added loads/drag | ~2.2–2.7 kn |
So for true solar-only indefinite cruising, your likely speed is only around:
If you use batteries to carry through night and rely on daytime recharge, these average speeds still apply over the long run.
These costs are approximate China fabrication/export numbers for a one-off prototype vs. batch of 20. Shipping, import duty, design engineering, and certification may add significantly depending on destination.
| Subsystem | Estimated Cost |
|---|---|
| Marine aluminum floats / legs fabrication | $40,000–$80,000 |
| Main triangle frame and structural weldment | $20,000–$45,000 |
| Living area shell, windows, doors, basic fitout | $35,000–$80,000 |
| Solar array, hinges, controllers, wiring | $18,000–$35,000 |
| 6 rim drive thrusters and controls | $24,000–$60,000 |
| Battery bank 4,000 lb LiFePO4 (~230 kWh) | $35,000–$60,000 |
| Power electronics / inverters / BMS / distribution | $12,000–$25,000 |
| Stabilizer system (3 units) | $12,000–$25,000 |
| Davit/crane | $3,000–$8,000 |
| 14 ft RIB + outboard | $12,000–$25,000 |
| Interior, plumbing, tanks, misc. systems | $15,000–$40,000 |
| Assembly, testing, margin | $20,000–$50,000 |
Total one-off estimate: $246,000 to $533,000
Reasonable planning midpoint: ~$360,000
| Scenario | Estimated Cost Each |
|---|---|
| Low end, efficient production | $180,000–$230,000 |
| Likely practical range | $220,000–$320,000 |
| Higher-spec outfitted | $320,000–$400,000 |
Recommended planning figure for batch-of-20: ~$260,000 each.
| Item | Estimate |
|---|---|
| Total solar area | 784 ft² |
| Installed solar | ~15.7 kW |
| Total buoyancy at 50% float immersion | ~21,888 lb |
| Extra buoyancy per extra foot immersion, one leg | ~768 lb |
| Estimated structure weight | ~12,000–18,000 lb |
| Payload left after structure | ~3,900–9,900 lb |
| Suggested stabilizer foil area per leg | ~20 ft² |
| Stabilizer cost, total 3 units | ~$7,800–16,800 (batch 20), midpoint ~$12k |
| Stabilizer weight, total 3 units | ~435–810 lb, midpoint ~570 lb |
| Propulsion power at 4 / 5 / 6 kn | ~5 / 8.5 / 15 kW |
| Battery usable energy | ~207 kWh |
| Battery range at 4 / 5 / 6 kn incl. hotel loads | ~138 / 109 / 77 nmi |
| Solar recharge time from empty | ~3–4 Caribbean days |
| Solar-only continuous cruising speed | ~2.6–3.0 kn without stabilizers |
| Solar-only continuous cruising speed with stabilizers | ~2.2–2.7 kn |
| One-off build cost | ~$246k–533k, midpoint ~$360k |
| Batch-of-20 cost each | ~$220k–320k, midpoint ~$260k |
If you want, I can next turn this into a more polished web-ready HTML page with: