Concept: Custom 40-ft high-cube marine-aluminum living module (legally a Panama-flagged catamaran yacht) + four nested frustum hull sections + four beams + cables, solar, LFP banks, electric thrusters. Target: thrifty full-time liveaboards, Caribbean island-hopping, stay out of hurricane season, moorings/anchor, Starlink, no diesel/sailing skill required.
Assumptions used for packing: each main section is a frustum ~33 ft long, ~2 ft small OD, ~5 ft large OD, ~10 mm wall; four identical parts nested small-into-large; flanges on the large ends stay outside. Taper gives ~0.09 ft diameter change per foot of length. Wall thickness implies an axial offset of roughly 0.7–0.8 ft per nested interface so the cones do not occupy the same metal.
| Item | Estimate | Fits 40-ft HC? (internal ~39.5 ft L × ~7.7 ft W × ~8.9 ft H) |
|---|---|---|
| 4 main hull sections nested “like cups” | ~35.0–35.5 ft overall stack (33 ft + ~3 × 0.73 ft offsets) | Yes, length-wise with ~4 ft spare. Outer diameter ~5+ ft fits width and height if laid along the floor (chocked). |
| 4 pointy end-caps nested | Much shorter; user intent is they nest inside the innermost main section or ride on the thin end with supports | Yes if they remain true cones of modest length. If the NA fattens or “boat-bows” them they may need to sit beside/on the stack instead. |
| 4 beams (one piece, <40 ft, ~45°) | Length set by geometry; must be < internal length. Probably 28–38 ft depending on exact attachment and deadrise of beams | Yes if cut to fit; may need to lie alongside the nested hulls or on top with dunnage. |
| Solar (roof + 3 ft wings), packed | Flat-packed modules + rails; ~50 m² deployed | Yes, standard packing. |
| Batteries, tanks, thrusters, ladders, walkways, cables, hatches, airbags, interiors | See weight table | Volume-wise yes if hulls take the long axis. Weight vs. payload: 40-ft HC payload is typically ~26 t; you are well under if estimates hold. |
If nested mains come out longer than ~38 ft after real flange/plate thickness, shorten the mains a few feet and lengthen the pointy caps (exactly as you suggested). NA should freeze LOA vs. the 24 m yacht threshold at the same time.
One frustum lateral area ≈ 33–34 m² × 10 mm ≈ 0.33–0.35 m³ of metal ≈ 900–950 kg before flanges, ring frames, the watertight bulkhead plate, hatches, and weld reinforcement. Use ~2,000–2,400 lb per section as a working number until the NA sizes scantlings.
| Part | Est. weight (lb) | Est. weight (kg) | Notes |
|---|---|---|---|
| 4 hull sections (plated + flanges + bulkhead plates) | 8,800–10,500 | 4,000–4,800 | 1 cm was a starting guess; NA may go thicker at joints or thinner amidships. |
| 4 pointy caps | 800–1,600 | 360–730 | Depends on length/shape the NA chooses. |
| Custom 40-ft HC living module (aluminum, ISO corners isolated/removable) | 5,000–9,000 | 2,300–4,100 | Lighter than steel HC; extra structure at 8 corners and solar attachments. |
| 4 beams | 1,800–3,500 | 800–1,600 | Function of section (tube vs. I vs. truss) and buckling/tension interaction with cables. |
| Cables, fittings, extra assembly winch points | 400–900 | 180–410 | |
| Solar array + racks (~50 m², 10 kW-class) | 1,500–2,400 | 680–1,100 | Marine-grade, walkable or not. |
| LFP batteries (see below) | ~2,000 | ~900 | Target ~100 kWh usable pack level. |
| 2 electric thrusters + controls + shafts/props | 400–900 | 180–410 | |
| Tanks (water, grey/black), airbags, hatches, ladders, walkways, railings | 1,200–2,500 | 540–1,130 | Empty tanks. |
| Minimal interior, electrical, Starlink, pumps, safety gear | 1,500–3,000 | 680–1,360 | Thrifty fit-out. |
| Lightship (empty, no people/water/fuel-as-water) | ~24,000–37,000 | ~11–17 t | Use 12–15 t as a planning midpoint until NA + shipyard weigh the prototype. |
Planning energy: ~50 kWh/day solar in typical Caribbean (see speed section). “2 days of solar output” → ~100 kWh usable storage. Marine LFP packs (UN38.3, BMS, cases) often land around 90–130 Wh/kg at pack level.
| kWh (usable, planning) | Weight (lb) | Weight (kg) | |
|---|---|---|---|
| Total (4 banks) | ~100 | ~2,000 (range 1,700–2,400) | ~900 (range 770–1,090) |
| Each of 4 banks (hull ends) | ~25 | ~500 (range 425–600) | ~225 (range 190–270) |
Put mass at the four hull extremities as you planned (rotational inertia + some lowering of CG). Each bank needs its own watertight compartment, hatch, ventilation/off-gas path, and isolation from the rest of the frustum. Airbags in each half-section are a good “float even if holed” idea; they must be inspectable and not chafe.
Solar area: 40 ft × (8 ft + 3 ft + 3 ft) ≈ 560 ft² ≈ 52 m². At a realistic marine STC packing of ~180–220 W/m² you get roughly a 9–11 kW array. Caribbean equivalent peak-sun-hours often ~4.5–5.5 in good months → on the order of 45–55 kWh/day to the batteries after realistic losses (dirt, heat, MPPT, wiring). Use 50 kWh/day as the planning number.
House loads (very rough): Efficient minisplit(s) + fridge + water + Starlink + lights in a 40-ft aluminum box in the Caribbean might be ~18–30 kWh/day with A/C and ~5–10 kWh/day with A/C off. Planning: 25 kWh/day with A/C, 7 kWh/day without.
Propulsion: No resistance curve exists yet. The table uses a placeholder power-vs-speed guess for a ~12–15 t, long, unusual cat in calm water after losses (not conservative for waves, fouling, or current). A naval architect’s resistance + propeller calculation will replace this entire table.
| Case | Conditions (as requested) | Est. speed | Est. distance | Logic (placeholder) |
|---|---|---|---|---|
| 1 | Typical Caribbean sun, 24/7 for days, A/C on, charge by day / use by night | ~3–4 kn sustainable average if motoring around the clock; ~4–5 kn if motoring mainly by day | ~70–100 nm/day if they choose to keep moving; or “unlimited” duration at slow speed while sun continues | ~50 kWh solar − ~25 kWh house ≈ 25 kWh/day for propulsion ≈ 1 kW average. Slow. Hops are better done as daylight sprints. |
| 2 | Same as 1, all A/C off | ~4–5+ kn average if 24/7; higher in daylight | ~90–130 nm/day possible in good sun if they keep moving | ~43 kWh/day leftover. Still modest power; hull efficiency unknown. |
| 3 | Batteries full, use them up in 5 h, no sun | ~6–7 kn (if the hulls allow it at ~15–20 kW) | ~30–35 nm | 100 kWh / 5 h = 20 kW to the system. House loads extra if A/C on—reduce speed or time. |
| 4 | Batteries full, use them up in 10 h, no sun | ~5–6 kn | ~50–60 nm | 10 kW class. More realistic for “get to the next island before dark” without sun. |
| 5 | Batteries full, 10:00, no clouds, solar + batteries, 4 h, no A/C | ~6–7 kn | ~24–28 nm in those 4 h | Morning-to-early-afternoon solar might add ~25–35 kWh on top of battery draw. Good for a short hop leaving after coffee. |
Most Caribbean hops are short; the useful mode is “leave at sunrise, battery + solar, A/C optional, arrive same afternoon.” Continuous 24/7 motoring is not this boat’s strength unless the NA finds unusually low resistance. Large, slow-turning props are the right instinct. Centerboards/daggerboards/fixed fins (item 11) are worth studying for cross-wind and yaw; they also add grounding risk and assembly complexity—trade study for the NA.
China can be substantially cheaper than EU/US yards for this class of work, but a novel tensegrity-ish cat with custom CSC container, lithium, and “yacht that ships as a kit” still needs real analysis (FEA, stability booklet, electrical, assembly, flag). Treat the ranges as 2020s-order-of-magnitude in USD; get written quotes. One competent firm doing 1–5 as a package is usually better than five vendors.
| # | Scope | Est. cost (USD) |
|---|---|---|
| 1 | Feasibility / design review – “can this work?”, load-path sketch, first weight/power/cost bands, red flags | $8,000 – $20,000 |
| 2 | Basic design – lines, structure concept, hydrostatics/stability, scantling approach, electrical architecture, beam/cable loads | $25,000 – $55,000 |
| 3 | Detailed production design – cut files, weld maps, robot-friendly nesting, BOM, tolerances for a Chinese aluminum yard | $70,000 – $140,000 |
| 4 | Formal engineering assembly sequence (including in-water lift-by-cable procedure, temporary winches, failure modes) | $12,000 – $28,000 |
| 5 | Compliance paperwork package (see sub-list) | $35,000 – $85,000 |
| 6 | Quality-control check after factory (drawings vs. metal, NDT sampling, dimensional, weld, anodes/isolation) – usually a paid inspection trip + report, not “class” | $6,000 – $18,000 per visit (travel extra) |
| 7 | Total (1–6, one prototype cycle, no full IACS class) | $160,000 – $340,000 A bundled quote from one firm might land ~$180k–$260k if scope is controlled. |
Item 5 sub-break (what “compliance” often actually means):
Using a 3PL in China to hold solar, thrusters, catalog LFP, tanks, fasteners, etc., kitting them into each structural container, and shipping to St. Maarten (or later anywhere) is the right model. Rough adders: $1,200–$4,000 per kit for storage, consolidation, export docs, and packing, plus a small monthly retainer if inventory sits. Cheaper than your own warehouse on the island for the first 20–50 boats. Confirm they can handle UN38.3 lithium as part of a mixed container.
Includes marine aluminum structure (hulls, living module, beams, caps), solar, LFP, thrusters, tanks, basic electrical, cables, hatches, airbags, ladders/walkways, anodes, and a thrifty interior allowance. Excludes NA fees, 3PL, ocean freight, duty (St. Maarten duty-free helps), and Caribbean assembly labor. Lithium and solar prices move; aluminum and labor less so.
| Quantity | Est. unit cost of all parts (USD) | Comments |
|---|---|---|
| First single prototype | $180,000 – $320,000 | One-off fixturing, extra NDT, design tweaks, higher scrap, no volume quotes on packs/thrusters. |
| Following order of 20 | $95,000 – $150,000 | Tooling amortized; still modest volume for lithium and custom extrusions/plate. |
| Following order of 50 | $80,000 – $125,000 | |
| Following order of 200 | $60,000 – $100,000 | Only if the design is frozen and the yard is running a real series. Interiors and lithium dominate the floor. |
| Item | Estimate |
|---|---|
| Ocean freight, 40-ft HC, China to St. Maarten (spot market) | $4,000 – $12,000 per box (volatile). Budget $7,000 midpoint + insurance + origin/destination handling. |
| 3PL kitting (above) | $1,200 – $4,000 |
| Assembly at a Dutch St. Maarten yard (in-water final, as you described) | Prototype: 4–8 weeks, $25,000 – $70,000 labor/crane/yard/temp winches/surveyor. Repeat units with videos + experienced crew: 1.5–4 weeks, $12,000 – $35,000. |
| Your extra assembly cables/winches (reusable) | $2,000 – $8,000 once, then reuse. |
Rolled-up “in the water, Caribbean” cost (parts + freight + 3PL + assembly), excluding NA amortized and your overhead:
Amortize the $160k–$340k engineering over the first 20 boats (~$8k–$17k each) or eat it in the prototype. Videos + instructions for kit customers are cheap compared with yard time; they also reduce your support burden.
You will not get “production car” margins, but you also should not price like a one-off custom metal yacht. After 20 boats you have some trial history, videos, and a repeatable kit.
| Offer | Suggested range after first 20 (USD) | Rationale |
|---|---|---|
| Fully assembled, in the water, Caribbean | $280,000 – $420,000 | Covers landed cost, warranty reserve, sales, a modest margin, and the fact that insurance/novelty still need a cushion. Too low and you cannot support customers; too high and you compete with used production cats. |
| Kit (customer + local yard assemble at their expense) | $160,000 – $250,000 FOB or CIF a major port | You skip yard risk and some working capital. Customer/yard must follow the engineered sequence; you still owe them drawings, videos, and a support channel. Price so that a competent yard’s labor still lands the boat under the assembled number. |
Catalog marine LFP packs with UN38.3 is the right starting point. Sea freight of lithium (Class 9) in a container is done constantly when packing, declaration, state of charge, and IMDG paperwork are correct.
The extra friction is your box is not a series-produced ISO container. A CSC plate with low or zero stacking weight is still a CSC plate if the approving body accepts the prototype/testing path. Some carriers and some terminals are allergic to (a) lithium + (b) non-standard boxes in the same sentence. That does not make it impossible; it means:
Opinion: it can be shipped as part of the kit more often than “never,” but it is a process problem, not a physics problem. Do not treat “we have ISO corners and a CSC plate” as automatic acceptance. Budget a logistics specialist for the first 20.
Joining the two large-end flanges of each hull on land, floating hulls and living module, then using temporary extra cables/winches so that tightening the permanent stays walks the beams and lifts the living module, is plausible if the NA designs the temporary load cases (uneven tension, one winch failure, wind, current, people on deck). Do not improvise this. Final batteries/solar/interior on the water can save yard square-meters; it also means working over the side with lithium and electrical—procedures and weather windows matter. Kit videos are high value for both your yard and a customer’s yard.