Fan Thrust Calculator
Calculate thrust produced by electric ducted fans (EDF), industrial blowers, and axial ventilation fans.
Fan Thrust Calculator
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What Is a Fan Thrust Calculator?
The Fan Thrust Calculator evaluates the thrust generated by Electric Ducted Fans (EDF) and axial ventilation fans. By enclosing fan blades in a shroud duct, tip losses are reduced, allowing high-speed, compact jets and hovercraft to produce concentrated static and dynamic thrust.
How to Use This Calculator
- Enter fan rotor diameter and blade pitch or duct exit diameter.
- Enter fan rotational speed (RPM).
- Review generated thrust in grams and Newtons.
Ducted Fan Momentum Thrust Formula
T_{\text{fan}} = \dot{m} \cdot v_{\text{exit}} = \rho \cdot A_{\text{duct}} \cdot v_{\text{exit}}^2Where rho is air density, A_duct is nozzle exit cross-sectional area, and v_exit is exhaust velocity through the duct.
Worked Example
Scenario: A 70mm EDF spinning an 11-blade rotor at 45,000 RPM producing 120 mph exit velocity.
Duct Diameter: 70mm (0.07m).
Exit Airspeed: ~120 mph (53.6 m/s).
Calculated Thrust: ~1,550 grams (15.2 N / 3.42 lbs).
Tips & Key Notes
- Ensure the intake duct has a rounded lip; sharp intake edges cause severe boundary layer separation and can reduce static thrust by up to 30%.
- A slight nozzle exhaust reduction (nozzle choke of 85%–90% FSA) increases exit velocity for high top speeds.
- Multi-blade EDF rotors (9 to 12 blades) produce a realistic turbine "whoosh" jet sound compared to loud 3-to-5 blade screeching props.
Frequently Asked Questions
What is FSA in ducted fans?
FSA stands for Fan Swept Area. It is the total interior cross-sectional area of the fan shroud minus the cross-sectional area of the central motor hub.
Why are open propellers more efficient than ducted fans for hovering?
Open propellers have much larger diameters, moving a larger volume of air slowly. Ducted fans move small volumes of air rapidly, making them ideal for high speeds but inefficient for static hover.
How does an EDF compare to a gas turbine?
EDFs run on electric batteries and brushless motors with zero flame or jet fuel required. They are cleaner, cheaper, and safer, though with shorter flight duration.
What causes thrust loss in RC jet ducting?
Long intake and exhaust tubes, internal obstructions, unfaired wiring, and sharp bends create friction and drag that reduce effective thrust.
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