What is the purpose of "dope" in the fabric covering process?

The purpose of "dope" in the fabric covering process is to seal the fabric and enhance its strength. Dope is a type of chemical treatment applied to the fabric, typically made from nitrocellulose or similar compounds. When applied, it creates a hard, protective finish that not only seals the fabric against moisture and environmental factors but also increases the overall structural integrity of the covering. This enhancement is critical for maintaining the durability and lifespan of the aircraft's outer fabric, ensuring that it can withstand the stresses of flight and various weather conditions. By providing this added strength, dope plays a vital role in the safety and performance of the aircraft.