Costs are estimated FOB Asia (China/Vietnam/Korea) including materials, fabrication, and welding. Transport to destination is excluded. Non-cylindrical shapes assume internal ribbing for buckling resistance.
Aluminum is preferred for weight savings and corrosion resistance in the splash zone. Estimated wall thickness: 6mm (0.25").
| Shape | Est. Weight (lbs) | Est. Cost (USD) | Hydrodynamic Rating | Manufacturing Complexity |
|---|---|---|---|---|
| Cylinder (3.9' Dia) | ~1,600 | $8,000 - $10,000 | High Drag | Low (Standard Pipe/rolling) |
| Stadium (Rect w/ Rounded Ends) | ~2,100 | $14,000 - $18,000 | Medium Drag | Medium (Welded plate + ribs) |
| Ellipse | ~2,000 | $16,000 - $20,000 | Low-Medium Drag | High (Complex forming) |
| Lenticular (Lens Shape) | ~2,200 | $22,000+ | Low Drag | Very High (Double curvature) |
| Ovate / Asymmetric Teardrop | ~2,100 | $18,000 - $22,000 | Very Low Drag | High (Complex forming) |
| Kamm-Tail Teardrop | ~2,000 | $15,000 - $19,000 | Very Low Drag | Medium-High (Flat rear plate) |
| Optimized: Wide Chord Airfoil | ~2,400 | $16,000 - $20,000 | Ultra Low Drag | Medium (Simple curves, internal ribs) |
Higher strength and impact resistance, but heavier and more expensive to fabricate. Estimated wall thickness: 4mm (0.15").
| Shape | Est. Weight (lbs) | Est. Cost (USD) | Notes |
|---|---|---|---|
| Cylinder | ~3,500 | $15,000 - $18,000 | Standard option for steel |
| Kamm-Tail / Airfoil Shapes | ~4,500 | $30,000+ | Expensive welding and forming required |
Drag is calculated for half-submerged legs (15ft draft) moving at the specified speeds. Power is the total propulsion electrical wattage required for 4 legs assuming a system efficiency of 60%.
| Shape (Dims) | Speed (MPH) | Drag Force (lbs) | Total Power (4 Legs) | Notes |
|---|---|---|---|---|
| Cylinder 3.9' Dia |
1.0 | ~ 75 lbs | ~ 450 Watts | Baseline. Drag scales linearly with length. |
| 1.5 | ~ 170 lbs | ~ 1,500 Watts | ||
| 2.0 | ~ 300 lbs | ~ 3,600 Watts | ||
| Stadium 3.5' W x 4.2' L |
1.0 | ~ 60 lbs | ~ 360 Watts | ~20% less drag than cylinder. Good compromise. |
| 1.5 | ~ 135 lbs | ~ 1,200 Watts | ||
| 2.0 | ~ 240 lbs | ~ 2,900 Watts | ||
| Kamm-Tail 3.1' W x 4.9' L |
1.0 | ~ 20 lbs | ~ 120 Watts | Best Value. ~75% drag reduction vs cylinder. |
| 1.5 | ~ 45 lbs | ~ 400 Watts | ||
| 2.0 | ~ 80 lbs | ~ 950 Watts | ||
| Wide Chord Airfoil 2.2' W x 7.0' L |
1.0 | ~ 12 lbs | ~ 70 Watts | Ultra Efficient. ~85% drag reduction. Fits 3 per container. |
| 1.5 | ~ 27 lbs | ~ 240 Watts | ||
| 2.0 | ~ 48 lbs | ~ 570 Watts |
Container Internal Width: ~7.7 ft. Legs are 30 ft long (fits lengthwise).
| Shape | Width Profile | Qty per Container | Stacking Logic |
|---|---|---|---|
| Cylinder (3.9' Dia) | 3.9 ft | 3 or 4 | 3 fit easily in a triangle stack. 4 fit if squared off (very tight on width). |
| Stadium / Ellipse (~4.2' Chord) | ~4.2 ft | 3 | Can stack 3 in a triangle, inverting the middle one for volume efficiency. |
| Kamm-Tail / Ovate (~4.9' Chord) | ~4.9 ft | 2 | Chord exceeds half-width. Can only stack 2 side-by-side (width ~9.8ft is too much, but actually 2x thickness fits). Note: 4.9' Chord leaves narrow aisle. Max 2 legs. |
| Wide Chord Airfoil (7.0' Chord) | 7.0 ft | 3 | Surprisingly efficient. Chord fits width (7.0 < 7.7). Thickness is small (2.2'). Can stack 3 legs vertically or triangularly. |
Question: Can we use 10 PSI internal pressure for strength and leak detection?
Verdict: Excellent. The circular cross-section naturally resists internal pressure (hoop stress). 10 PSI creates uniform tension, effectively pre-stressing the skin against buckling. This is highly recommended for cylinders.
Verdict: Problematic without ribs. Applying 10 PSI to a non-circular shape causes the flatter sides to bulge outward (like a balloon). This induces significant bending stress at the corners or curved transitions.
Verdict: Poor. The flat sides will bulge significantly under 10 PSI. This shape would require heavy internal framing to maintain geometry under pressure.
All shapes, if built with the estimated wall thicknesses (6mm Al / 4mm Steel), will easily withstand the hydrodynamic force of moving at 4 MPH. The critical load is the axial compression from the tensegrity cables. Non-cylindrical shapes (like the Kamm-Tail or Wide Chord) actually have higher stiffness (Moment of Inertia) in the direction of motion, making them excellent for this application, provided the internal ribs are welded correctly.
This shape offers the best balance of cost, drag reduction, and shipping efficiency. While it only fits 2 per container (vs 3 for cylinders), the 75% reduction in drag allows you to use significantly smaller thrusters and solar arrays, saving money and weight in the long run.
If you can accept the wider footprint (7 ft wide), this is the optimal engineering solution. It fits 3 per container (matching the cylinder shipping cost) and has the lowest drag of all options. It creates a very stable base for the seastead due to the wide chord.
Use the 10 PSI internal pressure strategy only for Cylinders. For the Kamm-Tail or Airfoil shapes, rely on internal ribs for strength and use external coatings/sensors for leak detection. Pressurizing complex shapes adds difficult engineering challenges with minimal buckling benefit.