Flight Log - 2022-11-12 - David Deavours's Wildman Goblin 5 Foam Core CF Fins

Wildman 5" Goblin with .5" Foam-core Carbon Fiber fins.  

Flight Date: 2022-11-12
Rocket Name: Wildman Goblin 5 Foam Core CF Fins
Flyer's Name: David Deavours
Motors: L1940X
Expected Altitude: 8,000.00 Feet
Wind Speed: 5.00 mph
Launch Site: Kloudbusters
Actual Altitude: 2,000.00 Feet

A tragic drag separation of this beautiful rocket.  Here's what happened.  This version of the Goblin has .5" foam core carbon fins instead of the 3/16" plate carbon fiber. I flew the 3/16" fin version of this rocket on the L1940x in a drag-race with John Williams at Mini Midwest Power 2022 with great success.  When I built the .5" foam core fin version, I copied my successful design to this new rocket.  This included 4 2-56 shear pins in the nosecone to hold in the main (it's HED).  Also, I have a single 2-56 shear pin in the booster section to hold it in during the flight.  

The race started great, I beat my competitor off the pad and was clearly pulling hard on the puncy L1940x motor.  At about 2,000' the wheels fell off - or more specifically the motor burned out.  The rocket was near if not in Mach so those big, thick fins suddenly pulled hard on the nosecone.  The single 2-56 shear pin proved not enough to hold the heavy AV Bay and Nosecone down to the booster and separated near mach.  The force sheared my eye bold on the AV bay and drove the Kevlar harness 2" into one fin.  The booster came down under a shattered drogue and core sampled.  The AV bay and nosecone continued up another 2,000' and the altimeter fired off the main charges at 900' as expected.  Bob recovered the main and nosecone section for me on his new Honda 110.  Jim recovered the booster section with about 3" of Argonia clay stuck in the tube.  

Photos on the pad and of the carnage are attached.  Lesson to all builders of large, draggy finned rockets. Use more shear pins than you think you need.  Tim used 2 2-56 pins and survived; my single pin was just not enough shear resistance!!  

1Aerotech L1940X


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