Estimating Stall Speed For A Trainer

I have been very interested in finding the calculation for stall speed. I have found it, but it is way to complicated for me to understand. So, I tried to make my own simplified version. I thought: Okay, what effects stall speed.

• Air density
• Maximum lift coefficient of the airfoil
• Wing loading

When I tried to go on this without much success, I decided to focus just on the relationship between wing loading and stall speed for a given lift coefficient and air density. Since the weather is not very good here in the wintertime, I went on the simulator and got the E-flite Apprentice with SAFE technology. Here is a graph I made with the relationship between wing loading and stall speed. 

The wing loading is the vertical (y) and the stall speed is the horizontal (x). What is basically happening is that the up until 61.8 grams/sq. decimetre of wing loading, for every 10 grams/sq dm. of wing loading I added, the stall speed or (more useful) landing speed increased by five kilometres per hour each time. After 61.8 grams per square decimetre, the landing speed was increasing by 3 - 4 kilometres per hour instead. I may repeat this test again just to be sure of these results. 

All of this means that my estimate for stall speed, with the airfoil of the Apprentice (which I'm guessing has a lift coefficient of 0.9 on landing) is: wing loading / 1.35 = stall speed. As far as I know, this would become less accurate after 60 grams/sq dm. or so because the relationship changes. 

Many people say that knowing the stall speed for an RC plane isn't useful because all you have is your eye which can't tell you exactly what speed the RC plane is flying at. This is true. 

But my suggestion is to set out some cones that your plane will have to fly over before it lands. By finding how far apart your cones are, and estimating your landing speed, you can say that if the RC plane went over those cones in x number of seconds, it's going at the right speed.