Durable semi-rigid flexible duct

A durable semi-rigid, flexible duct having an axis running the length of said duct and having an inner and outer surface, comprising:

• a pair of coaxial sleeves, including an inner sleeve and an outer sleeve disposed parallel to and about said inner sleeve;
• a resilient wound element disposed between said inner sleeve and said outer sleeve;
• wherein each of said inner sleeve and said outer sleeve constitutes an aluminum foil ribbon layer,
• wherein each of said sleeves has metallic properties,
• wherein said wound element imparts corrugations to said inner sleeve and said outer sleeve, said inner and outer sleeves being formed with a plurality of closely and evenly-spaced ridges embossed in between a pair of said corrugations, such that said duct is axially extendible between a compacted configuration suitable for storage and for shipping and an extended configuration suitable for installation in an air transport arrangement;
• wherein said layers of both said inner sleeve and said outer sleeve are of a predetermined thickness rendering said duct substantially rigid when in said extended configuration and enabling said duct to maintain its substantial rigidity upon extension from said compacted configuration;
• and
• wherein said closely and evenly-spaced ridges impart additional rigidity to said duct, causing said duct to be resilient and withstand heavy impact forces, which might crush the duct and reduce its diameter.