How do you calculate wing loading for a plane, and then determine if that wing loading is heavy, light or in-between? The prop chart in my engine-manual is pretty nebulous as to sizes and I've built a plane whose instructions say to consult the engine manual.

Lightness depends on the size of the model. A large model with a higher wing loading will fly similarly to a small model with a low wing loading. Best to either ask specifically about a particular plane or just gain experience with different models so you know for yourself.

[link=http://airfieldmodels.com/information_source/math_and_science_of_model_aircraft/formulas/index.htm]Formulas for Model Aircraft[/link]

Cafeen:
I have just finished building a deHavilland Beaver kit. I calculated it out to have a wing loading of 22.9 oz./sq. ft. The plane weighs in at 5.25 lbs, and the wings are each 32.5" to the cabin. The instructions say the plane should weigh between 5 and 5.5 lbs when finished, so the weight's right on the mid point. The full-size Beaver is a stol plane used to transport hunters/fishermen to otherwise inaccessible lakes in Canada. This model is to scale size. The wing loading is quite high I would think, to be an stol. I'm trying to find the proper size propeller for this plane, and I want to get a prop that is readily available. I'm using an O.S. 40 4-cycle. What would you suggest?

23 ounces on a 65" + wingspan isn't all that high, but it ain't gonna be a STOL aircraft.

You base prop size more on the engine than the airframe, but in this case I'd think a larger diameter, smaller pitch prop would be appropriate. (You want torque for shorter take off runs and better climb, rather than top speed.) Your engine manual should list a range of prop sizes, but I'd guess at something like a 10 X 5 or 11 X 4.

Can you look up the recommended range for props?
Dennis-