This analysis estimates the time required to install helical mooring screws into the sand using a lever bar and a dinghy with a 10 hp outboard motor. The calculations are based on typical Caribbean sand conditions.
The installation time depends on the diameter of the helical mooring screw, the depth of penetration, and the applied force. The following table provides estimates based on the given parameters.
| Screw Diameter | >Target Depth | >Estimated Turns | >Estimated Time | >
|---|---|---|---|
| 6 inches (152 mm) | 7 feet (2.1 meters) | 60-70 turns | >6-10 minutes | >
| 12 inches (305 mm) | 11 feet (3.3 meters) | 120-140 turns | >15-25 minutes | >
The lever bar is used to multiply the force applied by the operator, making it easier to turn the mooring screw. Below are the ideal bar characteristics for each size of helical screw:
| Screw Diameter | >Ideal Lever Length | >Weight | >Strength Requirements | >Recommendations | >
|---|---|---|---|---|
| 6 inches (152 mm) | 10-12 feet | >20-30 pounds | >Standard steel bar (e.g., 1/2-inch diameter) | Lightweight, stiffer materials like aluminum may suffice | >
| 12 inches (305 mm) | 15-18 feet | >40-60 pounds | >High-strength steel bar (e.g., 5/8-inch diameter) | Longer bar to reduce powering requirements; ensure ductility | >