Tips to Select an Airfoil

The airfoil is the heart of an airplane. The airfoil you choose should have characteristics suited to the way you want your model to fly. But there are hundreds of airfoils to choose from, so how do you make this important decision?

The final selection of an airfoil depends on your design’s mission profile or how you want your design to perform. For a sailplane you need high lift, low drag, and low pitching moments. For an aerobatic model a symmetrical airfoil will give it the ability to fly upside down equally well. For a sport model, A moderately cambered airfoil will provide a high enough lift coefficient, low drag and pitching moment coefficients along with a gentle stall.

You can watch this video to understand the factors to consider while choosing the right airfoil for your design:

Here is a summary of the topics discussed in the video:

· Airfoils can be characterized into 3 main categories:

1. Heavily cambered

2. Moderately cambered

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3. No camber or symmetrical

· To select an airfoil for your design, you should know how to read airfoil plots. These plots contain information, that can be used to compare different airfoils. You can use tools like airfoiltools.com or XFLR5 to analyze these plots.

· The next aspect to consider is the stall pattern. There are three major types of stall:

1. Sharp

2. Sudden Lift Loss

3. Gentle

· Pitching moment is the nose up or nose down tendency of the airfoil. Cambered airfoils have negative pitching moments, meaning they have a nose down tendency.

· Reynolds number affects the characteristics of the airfoil, so it must be considered while comparing airfoils. Generally, low Reynolds numbers mean lesser lift coefficient and higher drag coefficient.

· In Summary, first decide how you want your airplane to fly, then look at various airfoil plots that will allow this kind of flight, and choose the best one.

These topics are discussed in more details in the above video.