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NERO Projects H6 rocket Laminate skin
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Thin walled aluminium laminate skin
One of the design goals of the H6 rocket was to fly the rocket faster than the speed of sound (Mach 1). To achieve this goal, it was necessary to design the rocket construction as light as possible. For the skin of the rocket body, we had been looking for a thin-walled Aluminium tube. This type of tube however, was not for sale. That's why we have decided to make it ourselves out of 0.3 mm thick Aluminium foil. By wrapping this foil, which had been covered with adhesive three times around an Aluminium drum-like mould we obtained a spirally wound Aluminium tube of about 1 mm thick. It took us about one year to perfect this technique to a point that it could be used as a practical production method. A tube made in this way proved to be so strong that an 80 kg person could stand on top of such a tube with a length of 50 cm without it buckling.

To obtain a good bonding between the Aluminium foil layers it is necessary to remove the oxide layer. This can be done by etching the foil. For this purpose a 20 cm diameter PVC tube was turned into an etching bath. Before etching, the Aluminium foil is wound into a spiral, together with some wooden sticks which would assure that there is a gap between the layers. This made it possible to fit a large piece of the foil into the small etching bath. After etching and drying, the adhesive is applied to the foil and then it is ready for wounding onto the drum mould. Because the adhesive had to be heated in order to spread it optimally on the foil, the wounded foil had to be kept under tension all the time. If this is not done, air bubbles can form in the adhesive layer. To keep the foil under tension, a special piece of equipment, the 'spring winch', had to be developed. The 'spring winch' continually winds the foil bit by bit while the adhesive is spreading across the foil. Some pictures of this production process are shown below.

47.5 kB		 The Aluminium foil is wound onto the drum mould.

55.4 kB		 The drum mould is place in the 'spring winch'.
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