# How Can I Calculate The Thrust of a Given Propeller?

1. May 31, 2013

### sjmay

I'd like to know how to calculate the thrust of any given propeller

2. Jun 1, 2013

### SteamKing

Staff Emeritus
Not a simple calculation. In the past, model propellers were tested and the thrust values obtained were scaled up to full size units. Now, computational fluid dynamics (CFD) can be used for preliminary design purposes, but model testing has not been rendered entirely obsolete.

3. Jun 1, 2013

### sjmay

What if I were to assume zero free stream velocity?

4. Jun 1, 2013

### Simon Bridge

You and about every aerospace and marine engineer in the World!
But there has been a lot of work on this a you can get good ballpark figures for specific configurations.
See:

http://www.grc.nasa.gov/WWW/k-12/airplane/propth.html
... simplified theoretical framework courtesy of NASA.

http://www.gobrushless.com/testing/thrust_calculator.php
... a simple thrust calculator for specific kinds of prop.

So... how complex it is depends on what you want to know for.

5. Jun 1, 2013

### sjmay

The NASA link you sent me was very helpful, though it did seem a little too good to be true (the equations were very simple and easy to follow). I'm determining thrust for a propeller on a light RC airplane. In your second link, a specific thrust was given at a given altitude for a given RPM value. But isn't the free stream velocity also a critical parameter in determining propeller thrust?

6. Jun 1, 2013

### Simon Bridge

The NASA link is very simplistic - for an RC craft you want to guarantee more than you need and throttle back.
The thrust calculator seems a little optimistic - I think it is for static thrust only and they make a lot of assumptions.

You should check on RC enthusiast forums.

http://www.rcfaq.com/RPMSTATS/propfaq.htm