Especially with airships, the gasbags are often protected by an outer envelope. Some gasbags were also fitted with a manually operated manoeuvering valve at the top. This describes a large rigidly framed outer envelope containing several separate gasbags. Letting out the gasbags and the weight-saving measures were begun. The hull contained 14 hydrogen-filled gasbags. It was so successful that all the gasbags of "Macon" were made from it. The interior contains one or more gasbags, cells or balloons to provide lift. The ship remained suspended until the gasbags were inflated with hydrogen. By mid-1929 the ship's structure was nearly complete and its gasbags were inflated. This caused the gasbags to chafe against the structure, causing holes in the fabric. New, lighter, gasbags were also fitted.