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Design
Design
ALBA was my level 2 high-powered-rocketry certification rocket. It consisted of a cardboard body tube, a 3D-printed nosecone, a plywood fin assembly, and an aluminum boat tail. ALBA was initially designed through a combination of OpenRocket and CAD.
Boa ttails make rockets more efficient by reducing the wake drag of the rocket. The effect of ALBA's boattail was analyzed using COMSOL, a CFD software. ALBA's boat tail resulted in about an 8% drag reduction over a similar rocket without a boattail. However, any performance increase is offset by the weight of the boat tail. The objective of this project was not to make the most efficient rocket. I wanted to earn my L2 certificate and thought that a boat tail would be an interesting addition. I also wanted to practice manufacturing using a lathe.
Manufacturing
Manufacturing
The aluminum boat tail began as a cylindrical piece of aluminum. Using a manual lathe, it was first bored to the correct dimensions. To get the intended inner profile, I derived an equation for the depth of the cut as a function of the radial distance. This allowed me to create the inner tapered surface. I then created the tapered outer surface with an angled cutting edge. Since the boat tail also acts to hold in the motor and transfer the force to the body tube, a motor retainer was epoxyed into the boat tail. The retainer allowed you to insert the motor and then secure it by screwing on a separate piece.
The fins and centering rings were laser cut out of 6mm birch, and everything was epoxied together to create the fin assembly. The body tube was then cut and slid over the fin assembly. The nosecone was made in three parts that were epoxied together. The printer that I had available was not large enough to accommodate the entire nose cone, making this necessary.
Launch
Launch
IMG_0082.movALBA was launched in the middle of a frozen Lake Winnipesaukee in February, 2025. The rocket successfully launched on a J270 motor to just under 3000 ft and came down under parachute.
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