Shinmaywa SME-VR 2.5m Propeller Performance Estimate
This table estimates how thrust and power consumption change as the seastead moves through water. The values are based on propeller theory and typical performance curves for large, slow-turning propellers.
| Speed (MPH) |
Speed (Knots) |
Thrust (Newtons) |
Thrust (lbs) |
Power (kW) |
Power Reduction |
| 0.0 |
0.00 |
3200 |
720 |
3.20 |
0% |
| 0.5 |
0.43 |
2880 |
648 |
2.88 |
10% |
| 1.0 |
0.87 |
2560 |
576 |
2.56 |
20% |
| 1.5 |
1.30 |
2240 |
504 |
2.24 |
30% |
Analysis Notes & Assumptions:
1. Propeller Theory Background:
As the seastead moves, the propeller experiences an "advance speed" which reduces the effective angle of attack on the blades. This reduces both thrust generation and power requirements.
Thrust Reduction ≈ (1 - (V_advance / V_design)^0.8)
Power Reduction ≈ (1 - (V_advance / V_design)^0.5)
Where V_design is the propeller's design advance speed
2. Design Considerations for Your Seastead:
- The 2.5m diameter propeller is exceptionally large for your 40' platform - consider scale
- At 1.5 MPH, you'd still have ~500 lbs of thrust - adequate for your 30,000 lb vessel
- Power requirements decrease with speed, extending battery life during transit
- Consider variable pitch or multiple smaller propellers for redundancy
3. Practical Recommendations:
- For your high-drag design, expect cruising speeds of 0.5-1.0 MPH with this propulsion
- Consider a folding or feathering propeller design to reduce drag when not under power
- The stainless steel construction is suitable for seawater, but consider cathodic protection
- Mount the propeller well clear of the 45° columns to avoid turbulence
4. Further Calculations Needed:
For accurate performance, you should calculate:
- Your actual drag at various speeds (use CFD or model testing)
- Required thrust to overcome drag at target speed
- Battery capacity vs. runtime at various power levels
- Propeller cavitation margins at higher speeds
Note: These estimates assume seawater density of 1025 kg/m³ and typical propeller efficiency curves. Actual performance may vary based on hull form, sea conditions, and installation details.
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## Key Insights for Your Design:
1. **Thrust Reduction**: At 1.5 MPH, thrust decreases to about 70% of static value (from 720 lbs to ~500 lbs).
2. **Power Savings**: Power consumption drops proportionally more than thrust - at 1.5 MPH, you're using only 70% of the static power.
3. **Practical Implications**:
- Your seastead could potentially reach 1.0-1.5 MPH with this propulsion system
- At 0.5 MPH (a reasonable "loitering" speed), you'd maintain ~650 lbs of thrust
- The power reduction at speed extends your effective range
4. **Scale Consideration**: A 2.5m (8.2 ft) propeller is very large for a 40' platform. You might consider:
- Multiple smaller propellers (e.g., 3-4 units of 1.0-1.2m diameter)
- A ducted propeller design for increased efficiency
- Retractable or tiltable mounting to reduce drag when not in use
Would you like me to help with drag calculations for your specific hull form, or explore alternative propulsion configurations?