```html
Seastead Tension Leg Mooring System Analysis
>
>
Seastead Tension Leg Mooring System Analysis
1. Hoisting and Lowering Procedure for Prototype (1/2 Scale)
The proposed procedure for hoisting and lowering the helical mooring screws involves the following steps:
1.1 Preparation
- Position the prototype seastead in shallow water (e.g., 8 feet).
- Attach a floating rope to the mooring screw eye.
- Wind the mooring rope around the capstan wheel and secure it with a spring-loaded clamp.
- Ensure the capstan wheel is positioned to allow smooth sliding along the hex shaft.
1.2 Lowering the Screw
- The seastead crew uses the dinghy to hold the seastead in place and ensures the mooring screw is vertical.
- The captain drives the seastead away from the mooring screw, causing the capstan wheel to spin and lower the screw.
- The rope provides resistance, and the helical screw begins to sink into the seabed.
- The process is repeated until the screw is fully seated.
1.3 Hoisting the Screw
- Reverse the process: the seastead moves closer to the mooring screw.
- The rope is tightened, and the capstan wheel is rotated upward.
- Resistance from the seabed prevents the capstan wheel from moving upward with the screw.
- Multiple cycles of tightening and loosening are performed to extract the screw.
1.4 Ensuring Proper Operation
- During lowering, ensure the capstan wheel rests on the seabed and slides smoothly along the shaft.
- During hoisting, ensure the spring-loaded clamp holds the rope securely until tension is applied.
- Use extra rope (80 feet from the capstan to the seastead, 200+ feet on the other side) to minimize slippage.
2. Helical Screw Load Capacity
Estimating the load capacity of the helical screw in marine stainless steel:
2.1 Technical Specifications
- Diameter: 6 inches
>
- Length: 8 feet (102 inches)
- Escape load: 1,000 lbs
>
- Material: Marine stainless steel
>
2.2 Load Capacity Analysis
Using industry standards for marine hardware, a 6-inch helical screw with marine stainless steel construction can easily handle a 1,000 lbs escape load. The exact safety factor depends on the material grade and coating, but marine stainless steel (e.g., 316 or 321) typically has a yield strength of 25,000-30,000 psi.
3. Cost and Weight Estimation
Estimating the cost and weight of the helical screws with capstan wheels:
3.1 Prototype (1/2 Scale)
| Component |
>
Quantity |
>
Weight (lbs) |
Cost (USD) |
| 6-inch Helical Screw |
>
3 |
>
50 |
>
3,000 ($1,000 each) |
| Capstan Wheel (12-inch diameter) |
3 |
>
100 |
>
3,000 ($1,000 each) |
| Hex Shaft (8-foot length) |
3 |
>
30 |
>
1,500 ($500 each) |
| Total |
|
180 |
7,500 |
3.2 Full Scale
| Component |
>
Quantity |
>
Weight (lbs) |
Cost (USD) |
| 12-inch Helical Screw |
>
3 |
>
150 |
>
9,000 ($3,000 each) |
| Capstan Wheel (24-inch diameter) |
3 |
>
300 |
>
9,000 ($3,000 each) |
| Hex Shaft (12-foot length) |
3 |
>
90 |
>
4,500 ($1,500 each) |
| Total |
|
540 |
22,500 |
4. Operational While in Water
4.1 Time to Install/Remove Screws
With two people (one in the dinghy and one on the seastead), it is estimated that:
- Installing one screw: 15-20 minutes
>
- Removing one screw: 20-25 minutes
>
- Installing/removing three screws: 1.5 to 2.5 hours
>
5. Full Scale Scaling Analysis
5.1 Proposed Scaled Dimensions
| Parameter |
>
Prototype (1/2 Scale) |
Full Scale |
>
| Helix Diameter |
>
6 inches |
>
12 inches (Double) |
| Hex Shaft Length |
>
8 feet |
>
12 feet (1.5x) |
| Capstan Diameter |
>
12 inches |
>
24 inches (Double) |
| Escape Load |
>
1,000 lbs |
>
8,000 lbs (8x) |
| Seastead Thrust |
>
400 lbs |
>
2,000 lbs (5x) |
| Rope Length |
>
280 feet |
>
560 feet (2x) |
5.2 Feasibility Analysis
The scaled design appears to be feasible. However, the weight and cost will increase significantly. The procedure for installation and removal should remain similar, but additional considerations may be needed for handling larger components.
6. Conclusion
The proposed tension leg mooring system is viable for both the prototype and full-scale seastead. The procedure for installation and removal is practical, and the load capacity of the helical screws is sufficient. Scaling the design to full size may increase costs and weight, but the method should remain workable with careful planning.
>
>
```