Mounting of Deployment canisters

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Well-Known Member
Jan 22, 2009
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I in the mist of constructing my first dual deployment and want some advice or insight on how to mount ejection canisters.

Setup A
What I have seen is construction of the rocket in the anti-zippper configuration. The altimeter mounted in the forward section, with the ejection canister dangling down the rocket body the the aft section. I am under the impression that this is the prefer method.
Why ? or Why not ?

One setup actually had a heavy wire cable connected to a wood block where the canister was mount and dangled down the rocket body.

Setup B
The other is that the ejection canister is mount on the altimeter bay itself.

For setup A my concerns are:
In the case of the wire dangling down the rocket body,how to keep the ejection canister wire from tangling the parachute.

If I have a ejection canister actually mounted on the bulkhead of the aft section. How do I disconnect the wire running to the ejection canister to allow the rocket to seperate ?
Some designs use some type of connection to realease went the rocket seperates ? ( Banana plugs etc)

Setup B
Wires are not a concern they are mounted on the Altimeter bay.

Right now I looking at design a Setup A , only running the ejection wire down the rocket body inside a cardboard tube attached (glued) to the inside and use banana plugs at the aft bulkhead so that when the rocket is to seperate that the wire connection doesn't interfere.

Thanks in advance

Can't quite understand your two scenarios. Pictures are worth 1000 words. A quick sketch would help.

I put the ebay in the middle of the tube (by attaching two w/ screws, or gluing into one and attaching the other w/ screws.) The charges get attached to the ends of the ebay by various methods. The laundry get pushed OUT of either end. * are the charges
                |        |        |
        Aft    *|      Eb|ay      |* Fore

I love this forum.:) I came here to ask very similar to the same question. Regarding setup A, is there any thing bad going to happen if the canister is pointing the opposite way it should, or pointing sideways? I figure it will still be ejected either way due to the pressure, but I am wondering about, say, the canister blowing out a wall if it's pointed that direction.. Thank ye!

I'll take option B for smoothest deployment (Alex).

Option A and C (for lack of a name) will tend to push the 'chute back into the airframe. If your separation is vigorous enough, or your 'chute pack is loose enough, this may not be a problem. But it would suck if your chute got crammed back into the airframe and the two sections hurtled earthward in a flat spin connected by the shock cord. Assuming that your ebay is firmly mounted in the airframe, B is a better bet (IMNSHO). C adds even more complexity (which is seldom good, even though I'm often guilty of it).

As far a canisters blowing out a wall, unless the charge is real big, or you've got something hard in the end of a rigid cylinder, I wouldn't worry too much. I've seen charges made out of all kinds of stuff, including a wads of masking tape and those flimsy tubes that AT igniters come packed in.

You want to tailor you charges to your airframe volume. And don't forget to subtract some of the space that your 'chute, shock cord, etc. are taking up. Ground testing is always a good idea too. Use an Estes igniter and launch controller (w/ LONG leads) and save your expensive ematches.

nice pics BTW!

I would also take option B, but I'd like to top it with a little dog barf and a parachute protector on the side, please... ;)

why are you putting the ejection charge all the way "down there"? is it to avoid burning the recovery system?

instead, make a baffle system up high and put a reloadable charge/igniter holder inside it.
Yes to avoid issues with the charge and parachute.
When you say baffle , you mean a bulkhead with multiple holes drill ? and place the ejection canister behind ?

yes, that's what I had in mind. could be a tube with the charge at one end, and at the other end two holey bulkheads, or a holey bulkhead with a stainless steel mesh behind it ... that will take care of the hot particles and cool the gas quite a bit.

(for stainless steel mesh you can use a pot scrubber but not steel wool, that will ignite!)
Just as Ed said, use some dog barf and a protector and you'll be good. If you want to point the charge "away" from the 'chute, put it inside on your mount and point it "away" (toward the bulkhead). Baffle it if you prefer.

If your 'chute is perfect and unburned, but doesn't come out of the tube, you really haven't solved the problem, only created a different one which will result in at least as much damage.
Yes to avoid issues with the charge and parachute.
When you say baffle , you mean a bulkhead with multiple holes drill ? and place the ejection canister behind ?

The simplest method is to attach the charges to the bulkheads on each end of the electronics bay, assuming main above and drogue (if used) below. I hardly ever use a drogue so I don’t worry about “pushing” the chute down into the tube. I’m not sure myself if this is even an issue unless you would have a monster drogue as the charge pressurizes the whole tube and separates at its weakest point. If you need a connection that will separate I would suggest R/C servo connectors, this is what I use in my Sandhawk for separation charge and motor ignition. I mounted the male connectors in a small block epoxied to the side of the body tube with the wires running through a small plastic tube to the aft end of the rocket. The female ends are wired to a terminal strip on the ebay bulkhead (beside the apogee charge ) these separate quite nicely.