What does applying a finish coat primarily provide?

Applying a finish coat primarily provides a smooth and protective outer layer to the aircraft's fabric covering. This finish coat serves multiple important functions, including enhancing the durability of the fabric, protecting it from environmental factors such as moisture and UV radiation, and contributing to the overall longevity of the aircraft's covering system.

The smooth texture of the finish coat not only improves the aircraft's appearance but also reduces drag, which can be beneficial for flight efficiency. This coating creates a barrier that helps prevent wear and tear from external elements, making it crucial for maintaining the integrity of the fabric and the aircraft as a whole over time. Thus, the finish coat is essential for ensuring that the fabric covering performs well in various operating conditions while also maintaining an appealing look.