Project
Sugar / Kno3 cast engine

Construction

• These rockets were made out of 2" schedule 80 CPVC which has better mechanical properties at higher temperatures than PVC. Fuel was a 60 / 40 mixture of sugar and Kno3 mixed with water and melted in an electric wok at 300 degrees until all the water was evaporated and the sugar was in a molten state. The engine had a 5/8" round core and was lit with an electric igniter. The end cap and nozzle assembly were made with 2" PVC couplings containing rings of 2" PVC pipe secured in place with PVC glue and machine screws. The nozzle was cast out of Pourstone with a 3/4" throat. Nosecones were made from gauze filled with plaster. Each half was cast in a mold and then assembled, trimmed and painted. Fins were made from double thick mat board with a poster board laminate and attached to the rocket with fully threaded aluminium rods. The fin section was attached aft of the nozzle and vented with a number of 1/4" holes. The fin section was attached to the nozzle with 8 aluminium fully threaded rods.

Pros

• Rockets were stable and structurally sound.
• Good initial flights. Flights later in the month displayed some aerodynamic problems due to a design change.
• Easy to construct.

Cons

• CPVC is about 20 times more expensive than regular PVC.
• Machine screws add too much weight.
• Machine screws weaken the structural integrity of the nozzle.

Pictures

• One of the rocket launches.
• Me next to one of the rockets on the launch rail assembly.
• Me next to four rockets.
• The nozzle casing and fin section assembly before fins were added.
• Top view of the nozzle casing and fin section assembly.
• Fins added to the fin section assembly.
• Fin sections primed.
• Convergent and divergent sections of the nozzle being made.
• Bottom end of nozzles and convergent sections.
• Convergent sections added to nozzle assembly.
• Convergent sections secured into nozzle assembly.
• Finished nozzle assembly.
• Mold for nosecones.
• Finished painted fin section assemblies.
• A close up of the holes in the fin section that will join with pins from the nozzle section.
• Finished fins.
• Nozzle painted with high temperature paint.
• Another view of the nozzle assembly.
• Nozzle assembly attached to engine casings.
• Nosecone drying in mold.
• One half of a finished nosecone.
• Finished engines.

Video

• Three good flights.
• A flight later that month with stability problems.
• A flight later that month with stability problems.
• A flight later that month with stability problems.
• A flight later that month with stability problems.

CAD Drawings

• 414 rocket design.