Calculating lift force of a motorised hovercraft

In summary: You would need 3 electric motors total to power your hovercraft. One to power the lift, one to power the thrust, and one to power the hydrolics.
  • #1
orblight
1
0
Hello, I need help regarding calculating the lift force for a hovercraft. I found an equations online on thrust propulsion.

Equation →
T= π/4 x D^2 x (v + Δv/2) x ρ x Δv

D- diameter of propeller
v- velocity of incoming flow
Δv- additional velocity, accelerated by propeller
ρ- density of air (1.225 kg/m^3)

I know that the (v) would be zero initially as the hovercraft is not moving. The problem I have right now is that I do not know how to calculate the additional velocity from a given motor as it Only gives the rpm and not the velocity. If I were to convert rpm to rad/s then to m/s. This would only calculate the velocity of a point mass instead which is not the linear velocity I need. Or am I wrong? Thanks
 
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  • #2
Does this page help you understand better your equation?

Also, you are talking about «calculating the lift force» but you give an equation for thrust propulsion. You might be interested in this thread for lift force.
 
  • #3
Hi, I'm trying to work out what size electric motor is required for my hovercraft

I have a 6.5m x 3m hovercraft that is run by hydralics and a 3.9 Rover V8 motor which requires 150 horse power to lift it's 1200kg mass.
I am wanting to convert the motors over to electric and a diesel generator but not sure on what size Kw motor to install.
The lift fan has 5 blades at a diameter of 850mm and runs at 3000rpm

any help would be appreciated

Cheers
 
  • #4
1 horsepower is 0.746 kW, so you need 112 kW of power no matter the type of motor. The equation in this post can give you an estimation of what power you need just to lift the hovercraft. You still need additional power to push it forward though.

Electric motors are generally rated by their continuous power but they can reach much much higher peak rating. Check the specs carefully. The 150 hp of your V8 motor is the peak rating. The continuous power should at least greater than the power needed to lift the hovercraft.

Your electric motor needs to have a similar rpm compare to your engine or you will have to install a gear reducer to get a comparable rpm range. Gear ratio doesn't affect the power output.
 
  • #5
Thanks for your reply.

I was intending to remove the hydrolics altogether and install 3 separate electric motors... one for lift and two for the thrust therefore I believe I shall require less power due to the motor not having to operate the hydrolic pumps and motors and moving the fluid around

Cheers
 

What is the formula for calculating lift force of a motorised hovercraft?

The formula for calculating lift force of a motorised hovercraft is F = ρ * A * V2 * CL, where
F = lift force in Newtons
ρ = density of air in kg/m3
A = area of the hovercraft in m2
V = velocity of air in m/s
CL = coefficient of lift for the hovercraft's shape and design.

How does the density of air affect the lift force of a motorised hovercraft?

The density of air directly affects the lift force of a motorised hovercraft. As the density of air increases, the lift force also increases. This is because the lift force is dependent on the mass of air that is displaced by the hovercraft. Therefore, in denser air, more mass is displaced, resulting in a higher lift force.

What role does the area of the hovercraft play in the calculation of lift force?

The area of the hovercraft is a crucial factor in the calculation of lift force. The larger the area of the hovercraft, the more air it can displace, resulting in a higher lift force. This is why hovercrafts with larger surface areas are able to lift more weight.

How does the velocity of air affect the lift force of a motorised hovercraft?

The velocity of air also plays a significant role in the calculation of lift force. As the velocity of air increases, the lift force also increases. This is because a higher velocity means more air is being displaced, resulting in a greater lift force.

What is the coefficient of lift and how does it affect the lift force of a motorised hovercraft?

The coefficient of lift (CL) is a dimensionless value that represents the lift generated by the shape and design of the hovercraft. It takes into account factors such as the angle of attack, shape of the hovercraft, and airfoil design. A higher CL means a higher lift force, while a lower CL means a lower lift force. Therefore, it is important to consider the CL when designing a hovercraft for optimal lift force.

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