Alan Sherwoods neue L9/LZ36

15 litres (helium). All contained in the outer cover; no internal gasbags.

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You are right, it is a rigid frame with no internal gasbags. It is filled by feeding helium in at the tail, while there is a hole on the underside near the nose the air comes out. The gases do mix, but after feeding in 3 times the volume, the contents are 99% pure. I generally use twice the volume, getting about 97%. I leave the hole open to ensure pressure is equalized.

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I thought you asked how is the frame made, but perhaps you have edited it. So to answer that question: The frame is made from 0.3 mm pultruded carbon fibre rods. Its construction was very different from normal zeppelin practice. This airship has no internal gas bags, the outer cover is the only gas membrane. The structure and outer cover were made in unison. The rounded nose/tail and the central cylindrical section were made separately and then joined. Here is a brief description of the process. For the nose/tail, a wooden tool the same shape as the airship nose/tail was made, with grooves where the longitudinals go. Carbon rod longitudinals were then layed into these grooves, and fastened together at the tip. Strips of cover (4 micron metallised mylar) were then glued onto the longitudinals. This assembly was then removed from the tool. Rings were made from 0.3mm carbon rod, and inserted into the longitudinal/cover assembly, pushing it out into the final shape and stretching the mylar taut. The cylindrical section was made by taping a large sheet of mylar down to a table, then gluing on the longitudinals and transverse rods. This was then ‘rolled up’ (like sushi roll) into a cylinder, using round discs at either end. The transverse rods were then joined to form rings, and a sealing tape glued over the join. The end discs were then removed. Estimated weight of structure alone 12 grams.

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