After how many hours should the fabric be re-checked for tightness after doping?

The correct answer is that the fabric should be re-checked for tightness after 8 hours of doping. This timeframe is based on the fact that the doping process not only shrinks the fabric but also changes its adhesion and tension properties as it cures. After approximately 8 hours, the initial curing will have progressed enough to identify whether the fabric remains taut or has loosened. This step is crucial to ensure the fabric is properly secured and adequately supports the structure in which it is used, contributing to the overall safety and performance of the aircraft.

Monitoring the tightness at this interval also helps to assess whether additional doping may be required to maintain appropriate tension, as well as to prevent issues related to shrinkage or sagging that could affect aerodynamics or structural integrity. This practice is part of the meticulous care required in aircraft fabric covering to ensure longevity and reliability.