Seastead Design

A fully containerized, modular platform that packs into a single 45′ High Cube container — all buoyancy, structure, power, and propulsion included.

Container Envelope

Type

45′ High Cube

Shipping envelope

Length

44.6 ft

13.59 m

Width

7.7 ft

2.35 m

Height

8.9 ft

2.71 m

Max Gross

62,000 lbs

28.1 t

Target Buoyancy

27,500 lbs

at desired waterline

Structure weight is kept under the buoyancy limit to allow for humans, batteries, and provisions.

Triangle Frame & Living Area

Side Length

44.0 ft

equilateral triangle

Wall Height

7.0 ft

floor to ceiling

Walkway Width

3.0 ft

aluminum grating

Walkway Height

1 ft above floor

diagonal braces below

Doors: Two doors on the back side — 2 ft from left and 2 ft from right. Walkway wraps around the entire outside except where the dinghy is stored aft.

Internal Structure

Mid-point ring: A second triangle 22 ft on a side connects the midpoints of the walls at floor and ceiling.
All remaining spans are ≤ 22 ft, made from bolted-in smaller panels.
Roof is fully covered with solar panels.

Triangle frame (44′) → inner ring (22′) → infill panels
All walls 7′ high, assembled from three 10″-wide sections packed upright

Buoyancy Legs (Foils)

Quantity

trimaran arrangement

Length

21.5 ft

each leg

Chord

8.5 ft

NACA 0035 profile

Trailing Edge

0.5 ft clipped

fits within 8.9′ height

Submergence

50%

0.5 × 14.5′ in water

Built-in Ladder

Top half, front

above-water access

Each leg is attached near a vertex of the triangle. The thickest 3′ (1.5′ each side) is within the triangle footprint, but each leg is as close to its respective point as possible.

Heave plates are bolted onto the lower portion of each leg for wave-response damping.

RIM-Drive Thrusters

6 total — 1.5 ft diameter, one on each side of each leg, ~2 ft from bottom.
Fixed orientation → forward thrust; differential steering.
Can reverse one side / forward the other for zero-radius turns in harbors.
Power delivered via a conduit/pipe welded to the trailing edge of each leg.
No through-hulls in the legs; multiple airtight compartments for safety.

Batteries: ~25 % of displacement is LiFePO₄, located low in the legs. Each leg has its own charge controller, inverter, and feeds its pair of thrusters — triple-redundant power.

Container Packing Arrangement

Right Side – Legs

Leg 1 (round down, point up) + Leg 2 (round up, point down) stacked → just over foil thickness. Leg 3 (round down) forward of them.
Total width ~3–4 ft along right wall.

Left Side – Walls

Three wall sections stood upright (7′ tall, ~10″ thick each). ~3 ft total width on the left.

Center – Everything Else

Beams, floor/ceiling panels, walkway grating, dinghy (deflated), helical anchors, winches, thrusters, electronics, wiring, etc.

Key packing constraint: The 8.5′ chord of the foils fits within the 8.9′ container height by clipping the trailing edge 0.5′. Buoyancy is nearly identical to the full 8.5′ foil.

Dinghy

Type

14′ RIB

deflatable for shipping

Outboard

Yamaha HARMO

electric

Stowage

Sideways aft

centered behind living area

Two supports extend aft near the center, with two ropes down to the dinghy. When underway, the living area shields the dinghy from wind.

Tension-Leg Mooring

Anchors

6 helical screws

paired at each corner

Pull-down

3 ft (initial)

enough for Caribbean tides

Tension (target)

2,000–3,000 lbs

per leg, ~1 ft pull-down

Tidal Range

Very small (start)

Anguilla → eventual larger

Active tide compensation: A computer-controlled winch on each leg can pay out / haul in cable as the tide rises and falls. Geared very slowly for quiet, smooth operation.

Winch Type Recommendation

For slow, continuous length adjustment at 2,000–3,000 lbs tension, the ideal winch combines:

Helical-Gear Winch

High reduction ratio in a compact package. Very low backlash, excellent for holding position without power. Quiet when driven at low RPM.

★★★★★ quiet & stiff

Worm-Drive Winch

Self-locking — no need for a brake. Extremely smooth and quiet at very low speeds. Ideal for “set and forget” tension with occasional adjustment.

★★★★☆ self-locking

Planetary Winch (servo)

For precise computer control. Pair with a low-RPM servo motor and a helical output stage. Can do micro-adjustments automatically based on load cell feedback.

★★★★★ best for automation

Our recommendation: A planetary or helical-gear winch driven by a low-RPM brushless DC motor with an integrated load cell. Geared for a line speed of ~0.1–0.5 in/s — slow enough to be silent, fast enough to track a 6′ tide over 6 hours. Add an electromagnetic brake for fail-safe holding.

For larger tidal ranges (e.g., 6–10 ft), the same winch with a longer cable drum and a slightly higher gear ratio will work — the key is very low speed + high mechanical advantage to keep noise and power consumption minimal.

Connecting Two Seasteads

A walkway joins two seasteads, one behind the other, while underway.
Both onboard computers coordinate thrusters to minimize walkway movement, especially when a person is crossing.
Enables a real floating community.

Power & Control

Solar

Full roof coverage

all over the triangle

Battery

LiFePO₄

~25% of displacement, low in legs

Propulsion

6× RIM drives

electric, differential thrust

Redundancy

3 independent systems

one per leg (charger + inverter + thrusters)

Each leg has its own charge controller and inverter. The two thrusters on a leg draw from that leg's battery bank. A failure in one leg does not affect the others.

All dimensions chosen so that every part fits inside a single 45′ High Cube container — walls upright on the left, the three NACA‑0035 foils stacked on the right, and all remaining components (beams, panels, dinghy, thrusters, anchors, winches, wiring) in the center. Assembly at any shipyard worldwide.

Winch control algorithm for tide tracking: slow helical/planetary winch, computer-controlled, with load-cell feedback. Geared for silent operation and capable of handling both Caribbean micro-tides and larger ranges.