Small Step: Build Description and Flight Report

The Goal:
Have fun and test the $40 EggTimer recording altimeter.


  • Scratch built near-minimum diameter K rocket
  • Aerotech K1100 rocket motor
  • Eggtimer recording altimeter
  • Magnetic Switch by Featherweight
  • Rattworks AARD
  • BigRedBee GPS locator and tracking

  • Electronics

    The electronics include an Eggtimer $40 dual deploy, recording altimeter. The Eggtimer altimeter is a kit, which is simple to assemble with only basic soldering skills. The PC based software is minimalist. The software has a small learning curve, takes a little fiddling to connect to the altimeter, but works fine once setup. I recommend the Eggtimer and will be using this altimeter more often.

    The other component I have not used before is a magnetic switch by Featherweight. To power-up the electronics, simply wave a magnet outside the airframe, near the magnetic switch. The magnet included with the switch was too wimpy. I replaced the stock magnet with a large rare Earth magnet from McMaster.

    The BigRedBee GPS is installed in the wooden nosecone.

    The nosecone is programmed to pop at apogee. The RattWorks AARD will release the main parachute at 1000'.


    Flight and Aftermath

    Both the Eggtimer altimeter and the BigRedBee GPS suffered a power failure at approximately the same time, near apogee. The nosecone separated, but the main parachute did not deploy. Either the magnetic switches failed, or the shock of deployment disconnected both sets of batteries.

    I give credit to the Eggtimer. It survived the tent-peg from 10,000 feet and will fly again. The magnetic switches and the BigRedBee were completely destroyed.