Any tips for igniting AT D21's?

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Active Member
Jan 12, 2004
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Hi guys,

I have recently purchased a couple of AT D21's and have never used a composite motor before. I dont have an Interlock ingniter clip (only standard alligators on my 12V system), and was wondering if anyone has any good tips for ensuring reliable ignition? Can I clip onto the copperhead using alligators?


put a piece of masking tape on one side of the igniter lead. The place another piece of masking tape further up the lead, but on the opposite side. I usually have a little overlapping to help keep the tape connected. Then place the clips on the leads, where each lead comes in contact with a different side of the igniter.
I'd like to add a couple ideas to n3tjm's post. Toothed clips may pierce masking tape, shorting the igniter. Electrical tape or two layers of masking tape will help. A small piece of plastic tubing on one side of each clip is even better. Another thing to look for on copperheads is thin, copper threads hanging from the edges.... could creat a short. Pull those off. And creases in the copper may hide a crack. Nothing can fix this. I've sometimes heated the end of the copperhead with a lighter to separate the two conductors. Pull them apart alittle. Then standard clips can be used with no tape or tubing. Don't heat the business end!

Hold a match to the tail end of the igniter. The plastic between the two copper strips will burn away. Now you have two leads to attach your clips to.

I'll try the heating of the end of the igniter trick to separate the copper strips.

I presume that you can just attach the clips without masking tape etc to these strips?

One more question though....Do you need to plug the nozzle like estes and quest motors?

No, Just be sure the head is at the top of the propellant grain. It must light at the top.
You want to vent the plug that holds the igniter. If you don't, pressure will build up so fast, that when the plug does go, the sudden decompression may snuff out the motor.
Basically, not really a plug, but you'll need to use masking tape to keep the igniter at the top of the motor grain. Tape it in over the nozzle, then poke a hole in the tape to vent it.


One caveat - I had a D21 CATO on me last Sunday. In doing some Googling around, I have found out that this particular motor is *extremely* prone to CATO's.

You may want to fly it on a model that you consider "expendable" in case something bad happens.
Originally posted by GGoldy
No, Just be sure the head is at the top of the propellant grain. It must light at the top.

The D21 is a slotted grain motor. Gently poke the igniter into the nozzle with a slight angle toward the side of the case. Keep gently poking it as you turn the motor so you probe around the circumferance. When you find the slot, the igniter will go in about 2 inches. If you don't get the igniter all the way in the motor will not work correctly.
I never had one cato... but I have seen them cato. I also seen quite a few F72 and G80's bite the dust on ignition. I have seen a G80 blow an Initiator to bits...