# Help with Drag Coefficient

1. Jun 2, 2015

### louisba

I'd like to know how to work out the drag coefficient of a sheet of cardboard. I know the formula, but to get it you need the drag force which in turn needs the drag coefficient.

For reference, the cardboard is about 3mm thick and is roughly 60cm by 20cm. It has a 100g weight attached to the bottom and is sort of in the shape of a propeller. Can anyone tell me how to work out the drag coefficient or tell me what it would be?

Also, the "propeller" has slots in it and has angles of attack sort of like flaps on an aeroplane, would the angle of attack have an effect on the coefficient?

Thanks!

Last edited: Jun 2, 2015
2. Jun 2, 2015

### billy_joule

The angle of attack does affect Cd.

Wiki has Cd for various shapes (including flat plates):

http://en.wikipedia.org/wiki/Drag_coefficient

Of you could find it experimentally, with a stop watch and somewhere to drop your creation from.
Or a spring scale and a car... (take force values for various car speeds, though you may have to go quite fast to get the parallel flow situation..)

Doing it experimentally will likely be more accurate and, of course, more fun.

Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook