Design evaluation for storm survival and control in high winds
Primary Structure: Triangular platform (80ft sides, 40ft back) with enclosed living space (14ft wide) and open porches.
Buoyancy System: Three NACA foil-shaped legs (19ft long, 10ft chord, 3ft width), 50% submerged.
Propulsion: Six RIM drive thrusters on each side of the legs.
Control Challenge: Differential thrust may become insufficient in extremely high winds.
The proposed system consists of:
(Note: This is a conceptual representation)
With an adjustable bridle drogue system and three deep legs acting as keels/daggerboards, the seastead can be steered off directly downwind. The control range depends on:
Estimated angular range: ±30-45 degrees from directly downwind.
The three 19-foot legs (50% submerged) provide significant lateral resistance, similar to daggerboards on a sailing multihull. This allows for meaningful directional control even when dragged by a drogue.
To maintain approximately 6 knots (10.8 km/h, 3.08 m/s) while deploying a drogue for stability:
| Wind Speed | Wind Force (approx.) | Required Drogue Drag Area | Drogue Type Recommendation | Notes |
|---|---|---|---|---|
| 30 mph (48 km/h) | ~1,500 N on structure* | 0.5-1.0 m² effective area | Small parachute or series drogue (partial deployment) | Minimal drag needed; thrusters may still provide control |
| 40 mph (64 km/h) | ~2,700 N on structure* | 1.5-2.5 m² effective area | Medium parachute or series drogue | Begin to need meaningful drogue for stability |
| 50 mph (80 km/h) | ~4,200 N on structure* | 3.0-4.5 m² effective area | Large parachute or full series drogue | Significant drogue required; thrusters likely insufficient |
| 60 mph (96 km/h) | ~6,000 N on structure* | 4.5-6.0 m² effective area | Large parachute or heavy series drogue | Full storm conditions; drogue essential for control |
*Wind force estimates are approximate based on assumed exposed area of seastead structure. Actual forces will depend on exact geometry and wind profiles.
The Jordan Series Drogue (JSD) is an excellent candidate for this application because:
Implementation suggestion: Use a JSD with 100+ cones (typical for vessels of similar size). Incorporate a collapse line system that can "bundle" cones together to reduce their effective drag area. This would allow drag adjustment from perhaps 20% to 100% of maximum.
Another option is a parachute-style drogue with adjustable vents:
The proposed drogue system with adjustable bridle and winch control should work well for the following reasons:
Important consideration: The system must be designed to handle sudden shock loads if waves or wind gusts cause rapid tension changes. Winches should have load-limiting features or shock-absorbing elements in the lines.