Feedback wanted on 3X5: an L2 scratch build design for Freedom Launch

jhill9693

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First flight report:
  • H128W-8
  • Eggtimer TRS altimeter, main @ 650ft
  • Altitude: 935ft
Altitude underperformed the sim at 1250ft. Delay was too long, nearly came in ballistic with a noticeable whistle! Altimeter performed nominally, firing the main nearly the same instant as the motor ejection charge. X-chute performed beautifully and delivered the rocket gently.

Photo credit: Wes Munn
 

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jhill9693

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I passed the L2 written test, with 37/40 correct answers. This part worried me a little since I spent way more time building 3x5 than I did studying the practice test :p

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Unfortunately, the certification flight was not successful.

I used a loaned CTI case and a J270-12 reload from Ken with Performance Hobbies.
  • CSI J270-12 (4800ft)
  • Eggtimer TRS, main @ 650ft
  • GPS saved my bacon!
  • Altitude: 4549ft
CSI has a DMS-like ease of assembly.

However, the included e-match failed to light the motor. Second attempt with an “igniter that can light water” succeeded.

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It promptly disappeared into a cloud out of sight. I heard a worrying whistle… then my sister spotted the parachute. Relieved, I set out toward the last known coordinates, which weren’t live-updating. I didn’t realize at first, but the rocket was out of range and the Eggfinder LCD Receiver was not picking up the signal.

Unfortunately the parachute was just the parachute, a nose cone, and a bit of shock cord. But thankfully, the Eggfinder receiver recovered the signal and gave updated coordinates (and altitude—4549 feet—a personal record).

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I found the rest of the rocket nearly completely intact despite coming down under a 24” thin mill nylon drogue. Only slight zipper trying to start suggests that the TYVEK tape I wrapped around the end for the purpose was a good call.

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Upon recovering and disassembling Ken’s hardware, I realized the ejection charge malfunctioned and the drogue did not deploy when it was supposed to. I infer from this that the main deployed at ballistic speed and broke away. The resulting yank probably separated the coupler from the lower airframe and deployed the drogue.

I’m so glad I put in a GPS. It landed in a 4ft gully and the terrain interfered with the normal range of the signal.

KEY TAKEAWAYS:
  • Use an altimeter-controlled backup drogue charge, even if you think you don’t need it!
So, I guess now I get to come back in October to try again. At least the written test is done!
 
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jhill9693

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Nice straight boost, right into the cloud 😳
 

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