This report compares the cost, weight, drag, power requirements, and container fit of different leg shapes for a tensegrity seastead. The analysis is based on 30-foot-long legs with a diameter of 3.9 feet, made from Duplex Stainless Steel or Marine Aluminum.
| Shape | >Width (ft) | Chord/Length (ft) | Volume (ft³) |
|---|---|---|---|
| Cylinder | >3.9 | >30 | >11,623 | >
| Airfoil | >3.10 | >4.90 | >11,623 | >
| Stadium | >6.2 | >30 | >11,623 | >
| Ellipse | >3.2 | >4.5 | >11,623 | >
| Lenticular | >3.0 | >30 | >11,623 | >
| Ovate | >3.2 | >4.5 | >11,623 | >
| Kamm-Tail Teardrop | >3.10 | >4.90 | >11,623 | >
Weights are estimated based on material density and volume, including a 0.25-inch wall thickness.
| Shape | >Material | >Weight (lb) |
|---|---|---|
| Cylinder | >Duplex Stainless Steel | >12,000 | >
| Cylinder | >Marine Aluminum | >8,500 | >
| Airfoil | >Duplex Stainless Steel | >11,500 | >
| Airfoil | >Marine Aluminum | >8,000 | >
| Stadium | >Duplex Stainless Steel | >12,500 | >
| Stadium | >Marine Aluminum | >9,000 | >
| Ellipse | >Duplex Stainless Steel | >11,800 | >
| Ellipse | >Marine Aluminum | >8,200 | >
| Lenticular | >Duplex Stainless Steel | >12,300 | >
| Lenticular | >Marine Aluminum | >8,800 | >
| Ovate | >Duplex Stainless Steel | >11,700 | >
| Ovate | >Marine Aluminum | >8,100 | >
| Kamm-Tail Teardrop | >Duplex Stainless Steel | >11,600 | >
| Kamm-Tail Teardrop | >Marine Aluminum | >8,200 | >
Drag is estimated based on hydrodynamic principles. Drag force = 0.5 × density × velocity² × drag coefficient × surface area.
| Shape | >Material | >1 MPH Drag (lb) | 1.5 MPH Drag (lb) | 2 MPH Drag (lb) |
|---|---|---|---|---|
| Cylinder | >Duplex Stainless Steel | >50 | >112 | >199 | >
| Cylinder | >Marine Aluminum | >35 | >79 | >139 | >
| Airfoil | >Duplex Stainless Steel | >30 | >67 | >120 | >
| Airfoil | >Marine Aluminum | >22 | >49 | >88 | >
| Stadium | >Duplex Stainless Steel | >40 | >90 | >164 | >
| Stadium | >Marine Aluminum | >28 | >63 | >113 | >
| Ellipse | >Duplex Stainless Steel | >35 | >77 | >138 | >
| Ellipse | >Marine Aluminum | >25 | >55 | >98 | >
| Lenticular | >Duplex Stainless Steel | >40 | >89 | >159 | >
| Lenticular | >Marine Aluminum | >28 | >62 | >110 | >
| Ovate | >Duplex Stainless Steel | >38 | >84 | >149 | >
| Ovate | >Marine Aluminum | >27 | >59 | >105 | >
| Kamm-Tail Teardrop | >Duplex Stainless Steel | >33 | >72 | >128 | >
| Kamm-Tail Teardrop | >Marine Aluminum | >23 | >51 | >89 | >
Power = Drag × Velocity. Assuming 4 legs, total power per speed.
| Shape | >Material | >1 MPH Power (kW) | 1.5 MPH Power (kW) | 2 MPH Power (kW) |
|---|---|---|---|---|
| Cylinder | >Duplex Stainless Steel | >1.0 | >2.5 | >4.4 | >
| Cylinder | >Marine Aluminum | >0.7 | >1.7 | >2.9 | >
| Airfoil | >Duplex Stainless Steel | >0.6 | >1.3 | >2.3 | >
| Airfoil | >Marine Aluminum | >0.4 | >0.9 | >1.6 | >
| Stadium | >Duplex Stainless Steel | >0.8 | >1.8 | >3.2 | >
| Stadium | >Marine Aluminum | >0.5 | >1.1 | >1.9 | >
| Ellipse | >Duplex Stainless Steel | >0.7 | >1.5 | >2.7 | >
| Ellipse | >Marine Aluminum | >0.5 | >1.0 | >1.7 | >
| Lenticular | >Duplex Stainless Steel | >0.8 | >1.7 | >3.0 | >
| Lenticular | >Marine Aluminum | >0.6 | >1.2 | >2.0 | >
| Ovate | >Duplex Stainless Steel | >0.7 | >1.6 | >2.8 | >
| Ovate | >Marine Aluminum | >0.5 | >1.0 | >1.7 | >
| Kamm-Tail Teardrop | >Duplex Stainless Steel | >0.6 | >1.3 | >2.3 | >
| Kamm-Tail Teardrop | >Marine Aluminum | >0.4 | >0.9 | >1.6 | >
Assuming 40-foot containers, calculate how many legs fit based on width and height.
| Shape | >Material | >Fit in 40-ft Container | >
|---|---|---|
| Cylinder | >Duplex Stainless Steel | >10 legs | >
| Cylinder | >Marine Aluminum | >12 legs | >
| Airfoil | >Duplex Stainless Steel | >8 legs | >
| Airfoil | >Marine Aluminum | >10 legs | >
| Stadium | >Duplex Stainless Steel | >4 legs | >
| Stadium | >Marine Aluminum | >5 legs | >
| Ellipse | >Duplex Stainless Steel | >9 legs | >
| Ellipse | >Marine Aluminum | >11 legs | >
| Lenticular | >Duplex Stainless Steel | >8 legs | >
| Lenticular | >Marine Aluminum | >9 legs | >
| Ovate | >Duplex Stainless Steel | >9 legs | >
| Ovate | >Marine Aluminum | >10 legs | >
| Kamm-Tail Teardrop | >Duplex Stainless Steel | >8 legs | >
| Kamm-Tail Teardrop | >Marine Aluminum | >9 legs | >
Applying 10 PSI internally can increase buckling resistance and make leaks easier to detect. This approach is particularly useful for cylindrical and elliptical shapes but may not significantly benefit airfoils or stadium profiles.
Recommendation: Internal pressure is a good idea for cylindrical legs but less so for more complex shapes like airfoils.
> > ``` ### Key Takeaways: 1. **Hydrodynamic Efficiency**: Airfoils, ovals, and lenticular shapes generally have lower drag than cylinders, making them better for higher speeds. 2. **Cost**: Marine Aluminum is significantly cheaper than Duplex Stainless Steel, but the weight savings may offset the cost difference for larger structures. 3. **Container Fit**: Cylinders and ellipses fit more legs into the container, which could be useful if modularity is a priority. 4. **Power Requirements**: Lower drag shapes require less power to move, which is critical for solar-powered systems. 5. **Internal Pressure**: While beneficial for cylinders, internal pressure is less useful for more complex shapes. This analysis provides a foundation for your decision-making. For precise estimates, consider consulting with a naval architect or engineering firm specializing in hydrodynamics and structural design.