Upthrust calculations for hovercraft

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    Calculations Upthrust
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Discussion Overview

The discussion revolves around calculating upthrust for a remote-controlled model hovercraft. Participants explore various factors influencing upthrust, including air cushion pressure, fan output, and skirt design. The conversation includes both theoretical approaches and practical suggestions for measurement.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Experimental/applied

Main Points Raised

  • One participant seeks a formula for calculating upthrust, noting the importance of air cushion pressure and the use of a ducted fan with a 9V motor.
  • Another participant suggests estimating upthrust using the relationship between pressure and area, mentioning that the hovercraft's skirt dimensions and weight are also significant factors.
  • A third participant expresses difficulty in calculating static pressure, despite being able to determine velocity pressure from their engine output.
  • A later reply advises measuring thrust experimentally with an electronic scale rather than relying solely on analytical calculations.

Areas of Agreement / Disagreement

Participants do not reach a consensus on a specific method for calculating upthrust, with some advocating for theoretical calculations and others suggesting practical measurement approaches. Multiple competing views remain on how to best determine the necessary parameters.

Contextual Notes

Limitations include the dependence on specific definitions of pressure and the hovercraft's design, as well as the unresolved nature of static pressure calculations. The discussion does not clarify the assumptions behind the proposed formulas or measurements.

Who May Find This Useful

Individuals interested in model hovercraft design, aerodynamics, and experimental physics may find this discussion relevant.

nuttall86
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Hi,
usually don't ask for help but this is bugging me now!
I am working on a r/c model hovercraft, i have been trying to work out the upthrust but can not get a formula to do so.
I know the air cushion pressure is a factor, i am using a ducted fan for upthrust with attatched 9 v motor.

Any help would be very much appreciated.

cheers
nuttall86
 
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An estimate could be made from the cushion pressure, and the pressure from the mass of air that the fan can shift ( its usually stated with the fan/motor if its a complete assembly ).

Pressure = Force/Area

Upthrust (F) = Pressure x Area

Your hover craft skirt dimensions and its weight will be factors also.

Weight = mass x 9.81

Youll want a nice balence between weight and upthrust and skirt area.

If you know the mass of air your fan can shift, you can calculate the skirt pressure. Though if you make sure its over rated and you can vary the speed, you can just find it experimentally.

The pressure will depend on the skirt design, so you can play about with that.

You could make more detailed estimates if needed, sorry if this isn't enough, my level of physics is poor.
 
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Yeah, I'm trying to figure out the same thing, but I have no idea how to work out the pressure. If my engine output is 780m^3/h, where do I go from there? I can do the velocity pressure, which works out to about 2 kg, but I am stumped when it comes to the static pressure. Anybody know?
 
If you are trying to calculate this analytically, good luck. Get yourself an electronic scale and try to measure the thrust with your model.
 

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