Today I finished assembling the Polaron III stack. This rocket has all new bottles joined by aluminium Robinson couplings. Each aluminium coupling including washers weighs 9 gms compared to a brass one that weighs 21 gms. This means about 35 grams was saved in coupling weight.
Each bottle's base has been reinforced with fiber glass strapping tape to minimise the distortion around each coupling. I have also tried using minimum tape overall this time to reduce weight further.
The pink bands are thin flexible rubber aerodynamic seals for some joints. Made out of common kitchen rubber gloves.
A new set of fins was also made that are attached with rubber bands to the rocket, for shock absorption on landing, and together they are also lighter by about 20 grams compared to Polaron II's. The fins are made from plastic VHS covers.
The entire stack was pressure tested to 100 psi without leaks. The first flight will be around 120psi, with max pressure targetted for around 135 psi.
The payload section is still to be attached.
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