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Testing an Ejection Charge

hey!

I just recently recieved a 12 inch hexagonal nomex sheet and .25" kevlar cord for my clustered fatboy....i'm using 9 oz. in the nose cone..putting a

110 db personal security alarm in the rocket and a 24 inch parachute....i want to test if 3 d motors will eject all this crap outta a 2.6" tube...this test is gonna cost me 12 bucks =(!!!, but it's needed... what it a good way to retain the rocket while the motors are burning? or is there another method i should use to do this test....or should i just have faith and launch the rocket to 800 feet and hope the ejection charges work?

Thanks,

-Vishal

Reply to
Vishal
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I have done this with single engine ABC Estes engines by taping the model to its launch pad rod win several places with tape...... I suppose the same concept would work if you staked the pad down ?

shockie B)

Reply to
shockwaveriderz

Don't bother with the ground testing and save yourself a few motors. In a FatBoy, the area that is pressurized by the ejection charge is relatively small. It does not take much BP to do the job. I would not worry about it, especially with three ejection charges.

What I would worry about is the 9oz of nose weight. That seems like an awful lot. I have a 3x24 cluster Fatboy, and the entire rocket weighs 7oz empty - this includes .062" G-10 fiberglass fins. My nosecone weighs 3oz total, and the rocket flies nice and stable.

-- Joe Michel NAR 82797 L2

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Reply to
J.A. Michel

Hi Vishal, My son and I have a pair of FatBoys that operate in the steriod mode. His is a single 24mm mount that goes quite fast on a G55. There is about 1 1/8 oz nose weight in his. If flies fine on all 24mm motors. Mine is the FastFat. It has a 29mm motor mount. On my first test flight, it warbled real good coming off the rod on a G64. I dumped another two shotgun shells of pellets in for a total of 3 3/8 oz. Now it is a stable flyer on the G64 and G125 motors.

If you are really worried about ejection charge forces, then do a simple and cheap test. Install an A8-3 motor in one tube. Wrap it with masking tape to provide a tight fit. Plug teh other motor holes with wads of masking tape or some such. You will be pleasently suprised when the nose cone pops off ample pressure.

steve

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