Here is one of the few propellor models I could find. I know it is not for a model airplane, but maybe you can work around with it.
If that won't do, them search for a tutorial on propellor design on model airplane forums, or anywhere else for the matter.
I know this tutorial is for SolidWorks, but perhaps you also can work around with it.
http://www.nmine.com/solidprop.htm
And if you ever need anything else for inventor, the following site has been very helpful to me, with a large library of free downloads:
http://www.cbliss.com/inventor/index.htm