Flight Log for 7 December 1997, Monroe, WA

Overcast appr. 4000' AGL, wind S 2-5; changing to heavy rain appr. 12:30 pm.
Model
Flt
#
Recovery Type
Motor
Comments
Fat Fat Boy
5
18" plastic parasheet Estes D12-7 core, 3x Quest C6-0 outboards air started with Jet-X wick. There was only time for one flight before the rain started, what with helping a new flier prep, talking about a few things, and fielding comments on the motor setup in the Fat Fat Boy.  I had the motors set up for the core motor to ignite with a conventionally installed Estes igniter, and identical lengths of Jet-X wick, each embedded in the nozzle of the D12 core motor and the nozzle of one outboard.  I took great care to ensure that all Jet-X wick segments were in contact with the propellant in the outboard motors, and fixed everything in place with small balls of wadding -- I feared that the Estes earplugs and Tiger-Tac plugs would damage the pyrogen on the Jet-X wick.  All prep was done the day before, to allow taking plenty of time and working in a more controlled environment than the back of a car.
On ignition, the D12 came to life immediately, and lifted the model clear of the pad.  With two ounces of nose weight and a full motor load (D core and C outboards), this model weighs around eight ounces, and a D12 can safely lift up to 14 in calm conditions -- there was no problem with the liftoff, and in fact the rocket tracked as if on rails, despite only 3/4 caliber stability margin (according to VCP).  The core motor burned normally, and the rocket then coasted for a second or two before the outboards ignited.  I had thought from viewing the launch that all three ignited together, but another observer reported a delay of a fraction of a second on one ignition -- but even with that, the rocket changed course very little if at all (the advantage of air starting clusters), and boosted like a scalded cat.
Unfortunately, it seems the D12 had a short delay -- best guess based on my recollection and that of the other observer I mentioned is that the delay was no more than 5 seconds, possible as little as 4.  As a result of this short delay, the core motor deployment occurred almost immediately after outboard burnout, and the high speed of the rocket caused three of the six suspension lines to strip off the parachute.  Even with only a streamered parachute, though, the rocket landed slowly enough on the soft ground to avoid damage.


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