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8.2.14 The pod stuck on my boost/glider and the thing crashed. What is wrong?




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This article is from the Model Rockets FAQ, by Wolfram von Kiparski with numerous contributions by others.

8.2.14 The pod stuck on my boost/glider and the thing crashed. What is wrong?

You've just been shot down by the "Red Baron". If the pop pod
stuck, try sanding to loosen things up a bit. Or dust the
mating surfaces with powdered graphite, Teflon, or even talcum
powder. Check the action of the pop pod when
deploying. Streamers or parachutes have a nasty habit of
catching on things that you didn't want them to, like glider
wings.

Sometimes fastening the recovery system to the pop pod in a
different manner will prevent tangling. I use an external
Kevlar line that is glued to the pylon root, but use strapping
tape to fasten the line to the end of the tube just below the
nose cone so the line is opposite the glider. That seems to
help, at least for me. Ballasting the pop pod can also help,
especially if ejection occurred long before apogee.

Some pop pod systems are specifically designed to prevent this
problem, Try one of them.

One I favor particularly on smaller gliders is to skip the pop
pod and go back to a fixed pylon like the old Sky Slash and
Falcon. To keep it NAR legal, you tape a small streamer to the
motor casing, and wrap it tight before installing the
motor. Use a tube that is slightly loose inside to allow for
the streamer.

A mid ejection two piece pop pod eliminates the string that is
the common cause of the red baron. The down side is another
small piece to have to search for.

In the mid 70's Greg "Fat Albert" Stewart published his "Baron
Killer" pop pod. It shifts the motor back much like the
original Astron Scout, and tumbles down. Small fins on the pop
pod keep it legal for competition. He also used nested square
brass tubing to attach the pop pod to the glider, a very
positive attachment. Danger! bad ASCII art follows:

		\ pod
		 ------------------------------
				====|__________ 1/8" square K&S brass
				tube with
						3/32" square tube
						inside
 
			________
		________|______|______________ more 1/8" square brass
		tube \
			fuselage

Another Red Baron proof pop pod is the shotgun cluster
pod. Shotgun refers to an over and under or side by side
cluster pod arrangement, so named because it looks like the
business end of a double barrel shotgun. For B BG you use a
cluster of 2 A3-4T motors. The bottom one (i.e. closest to the
boom) is ignited on the pad. A 2" piece of thermalite in the
nozzle of the top motor is stuck in the exhaust of the first
motor. It ignites the second motor just about when the first
one burns out. About 3 seconds after that burnout, the first
ejection charge fires, separating the pod, but deploying NO
recovery system. Thus no red baron. A second later, after the
pod has fallen free, the second ejection deploys a chute or
streamer. It works very nicely, especially when the
alternative is to go to a fatter and heavier motor casing (2
A3s vs a single B4). You can also cluster two motors of
different delay, and ignite both at the same time.

You can also have the opposite problem, where the pop pod
falls off too soon, sometimes under power. First check the
fit. If it is too loose, use tape to make it tighter. This
could also happen at launch, where the glider is blown off the
pop pod by wind, or just after launch due to a structural
failure. Use a Power Tower type launcher to fly a glider and
provide additional support for the glider on the pad. Some pop
pod hooks, like the molded Apogee hook, are designed to
prevent premature glider separation.

 

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