30 ft long • Same buoyancy volume as 3.9 ft diameter cylinder (≈11.94 ft² cross-section)
| Shape | Frontal Width (ft) | Cd (streamlined) | Cd×Width | Drag vs Cylinder | Notes |
|---|---|---|---|---|---|
| Cylinder (baseline) | 3.9 | 1.00 | 3.90 | 100% | Easy to manufacture |
| Stadium (racetrack) | 3.5 | 0.80 | 2.80 | 72% | Simple to fabricate |
| Ellipse | 3.4 | 0.65 | 2.21 | 57% | 3.4×4.8 ft approx |
| Lenticular | 3.3 | 0.60 | 1.98 | 51% | Lens-like symmetric |
| Ovate | 3.2 | 0.50 | 1.60 | 41% | 3.2 ft wide × 4.5 ft chord (user spec) |
| Kamm-Tail Teardrop | 3.1 | 0.35 | 1.085 | 28% | 3.1×4.9 ft (user spec). Excellent compromise. |
| Airfoil (optimized) | 2.8 | 0.30 | 0.84 | 22% | ~2.8×6.0 ft. Best performance, harder to build. |
| Optimized Strut | 2.6 | 0.25 | 0.65 | 17% | Modern low-drag section with moderate thickness. |
| Shape | Marine Alum Weight (lb) | Marine Alum Cost (USD) | Duplex SS Weight (lb) | Duplex SS Cost (USD) | Fit in 40ft Container |
|---|---|---|---|---|---|
| Cylinder | 1,650 | $7,500 | 2,450 | $14,800 | 3–4 |
| Stadium | 1,720 | $9,800 | 2,550 | $18,500 | 5 |
| Ellipse | 1,740 | $10,200 | 2,580 | $19,200 | 5 |
| Lenticular | 1,760 | $10,500 | 2,610 | $19,800 | 5 |
| Ovate | 1,780 | $10,800 | 2,640 | $20,100 | 6 (alternating) |
| Kamm-Tail Teardrop | 1,810 | $11,200 | 2,680 | $20,900 | 5–6 (alternating) |
| Airfoil (optimized) | 1,850 | $13,500 | 2,750 | $24,500 | 4–5 |
| Optimized Strut | 1,830 | $13,000 | 2,720 | $23,800 | 5 |
*Costs include material, rolling/forming, welding, hard points, and basic internal baffles. Asia (China/Vietnam) fabrication. Aluminum 6mm, Duplex SS 3mm wall. ±25% uncertainty.
| Shape | 1.0 mph | 1.5 mph | 2.0 mph |
|---|---|---|---|
| Cylinder | 125 | 281 | 500 |
| Stadium | 90 | 202 | 360 |
| Ellipse | 71 | 160 | 285 |
| Lenticular | 64 | 143 | 255 |
| Ovate | 51 | 115 | 205 |
| Kamm-Tail Teardrop | 35 | 78 | 139 |
| Airfoil (optimized) | 27 | 61 | 108 |
| Optimized Strut | 21 | 47 | 83 |
Assumes two 2.5m submersible mixers, 60% overall propulsive efficiency (realistic for large thrusters).
| Shape | 1.0 mph | 1.5 mph | 2.0 mph |
|---|---|---|---|
| Cylinder | 1.7 kW | 5.7 kW | 13.5 kW |
| Stadium | 1.2 kW | 4.1 kW | 9.7 kW |
| Ellipse | 1.0 kW | 3.2 kW | 7.7 kW |
| Lenticular | 0.9 kW | 2.9 kW | 6.9 kW |
| Ovate | 0.7 kW | 2.3 kW | 5.5 kW |
| Kamm-Tail Teardrop | 0.5 kW | 1.6 kW | 3.7 kW |
| Airfoil (optimized) | 0.4 kW | 1.2 kW | 2.9 kW |
| Optimized Strut | 0.3 kW | 0.9 kW | 2.2 kW |
Yes, I agree that 10 psi internal pressure would work well for all the closed shapes listed (cylinder, ellipse, lenticular, ovate, Kamm-tail, stadium, etc.).
Internal pressure puts the shell in tension, which dramatically increases resistance to buckling under compressive loads and lateral water pressure. It also makes leak detection trivial (pressure drop = leak). This technique is commonly used in aircraft fuselages and some marine structures. All the shapes you listed are closed pressure vessels and can use this method effectively.
Assumptions: Half leg submerged • Seawater • Cd values are for streamlined orientation at these low speeds (Re ≈ 4–8×10⁵) • Hard points at both ends • Legs must survive 4 mph lateral load as a column/beam without buckling (pressure helps significantly).
All numbers are engineering estimates (±25%). Detailed FEA and tank testing recommended before construction.