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Deployment Bag Question

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fireone

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Since Level 1 is out of the way I am looking foward to Level 2. I have herd good and bad about Deployment Bags and I wanted to get a few more opinions on them. If anyone has had expirence good or bad please let me know your opinions please.
 

edwardw

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I love deployment bags. :) Makes putting a parachute in so easy. And a lot less worries. I usually use them with a small pilot chute if I'm not recovering the two pieces separately - that way you get it to actually pull out of the bag. Ohterwise it might just eject and you get the 'parachute in a bag' recovery. Messy. But if you split the two sections or use ARRD or Tether recovery you can use the drogue to pull out the main. Hope this helps and I'm not just rambling. www.info-central.org has a good page on Deployment bags :)

Edward
 

g_boxwood

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I agree entirely with Edward; I've used Rocketman dbags a number of times now and I never had a failure; that's because I like to use a pilot (my thrustful one is a standard LOC 24") to extract the main from the bag (both the drogue and the bag are then kept attached to the main apex, in the 'attached mode' setup (opposed the 'free-bag' setup)). I also started from Rocketryonline INFOCentral: I then got a reply from Dean Roth himself on the ROL Forum (recovery section) to clear my mind a bit more. Just consider that the rocketman dbags You'll see on ROL are the old ones: new models are slightly different and they incorporate a Nomex loop (both on the inside and the outside) to attach the pilot (it was custom sewn by Dean in that article). If You are interested in a dual-deployment from a single compartment (ARRD or similar) setup just let me know 'cause I'd like to share what I came out with during *my* speculations (for my L2 bird as well); I posted a thread about that

http://www.rocketryforum.com/showthread.php?s=&threadid=3983

but never got any particularly helpful hint/reply.

Ciao,

Giacomo
 

kgholloway

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If you wouldn't mind posting it I'd definately be interested in your thoughts and experience with deployment bags and "drogue to main" deployment. I've got one of Chris Turner's 11.5" V2 kits that I'm working on and the drogue to main recovery option is one that I've been looking at.

Ken Holloway
 

g_boxwood

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Glad You’re interested Ken. Now, first things first; I was introduced to this setup by TAP member Juergh Thuering (Tripoli Prefect of Switzerland and Swiss Team Ariane, TRF member as well) some months ago: that's why I referred to this tech as *my* (in the previuos post).

When I asked him, Juergh pointed me in the following direction:

http://www.argoshpr.ch/Images/Ariane020623_IgnitionBoard/P6220048.JPG

The picture shows the inside of the Ariane main airframe (PML 11.4"); BTW the red-anodized boxes screwed to the bulkhead are totally pyro-free "ARRD": they're servo actuated and have been designed, manufactured and throughly tested by Juergh in a great number of flights (EMR2, Electro-Mechanical-Release or something like that).

As You can see two channels are mounted inside the tube and they hold the black powder canisters; the inside channels (IC) bring the canister ABOVE the main deployment bag: this way no gasses have to by-pass it (as if the charges were to be fired from the bulkhead).

An important issue about this setup is that the fit between the main dbag and the airframe has to be LOOSE for the drogue/pilot to succesfully extract the dbag itself.

That may become more of a challenge in smaller diameter airframes (not that much of a concern in 7.5" tubes and larger but I never dealt with them). Some mods may be required: in my latest project, for istance, I had to fit a Rocketman R9CXP/R12C (roughly the same volume since the ProXP is thicker) into a 5.5" airframe; Rocketman reccomends a XL dbags for both but that bag is 6.5" in diameter and it fits super-tight even without the internal channels! Solution was to modify the XL dbag bringing its diameter back to that of a Medium-sized Rocketman bag (around 4.5"); since the XL is reasonably longer, careful packing of the chute prooved that the extra length could compensate for the reduced diameter, providing the necessary loose fit WITH the channels installed. Or You could simple switch to the previous dbag size (using a L instead of a XL, …) if You see You are still able to pack the 'chute in it (and if You are confident that the 'chute WILL deploy successfully THE WAY You packed it). I want to repeat that this is necessary in smaller diameter airframes. Nonetheless the Ariane LRB and SRB (3" (sure) and 4" (not sure)) use the same setup with one channel only; here are the pics:

http://www.argoshpr.ch/Images/Ariane020623_IgnitionBoard/P6220068.JPG

http://www.argoshpr.ch/Images/Ariane020623_IgnitionBoard/P6250007.JPG

In the main airframe (and IF space isn't an issue) the channels are two because they hold two canisters for redundancy; You may think to replace the two channels with a single canister holding two e-matches (or with a single channel holding two canisters); consider however that using two channels helps with the fit: the bag is held by the channels and the friction is greatly reduced as it is pulled out (less surface contact). If using one channel only, the bag will contact a larger area of the airframe itself (and it will be pulled out asymmetrically).

Building the channels may represent some unnecessary extra-work; You may think that in larger diameter rockets the charges fired from the bulkhead have plenty of room to by-pass the bag and eject the nosecone: that is right but the channels make for a cleaner and safer setup and they're definetely worth it (I would have done anything in my power to avoid doing that extra job but ended up with no better and/or safer solutions). Since the bag has some length of shock cord between the shroud lines and the bulkhead it may seem possible that the charges push it forward in the airframe while by-passing it, resulting in some kind of internal tangling and 'dirty' setup.

I got carried away: sorry for having been long; hope this may help You develop better solutions; I'll post some pictures of my channels in the next messages.

Ciao,

Giacomo
 

g_boxwood

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Here are my channels: made from LOC MMT-1.52 sliced lengthwise; the BP can holder is a burned Estes B6-4; the tube that runs along is a FirstFire container and is used to route the e-match wires down to the aft end.
 

g_boxwood

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The channels are stiffened with expanding foam; here it has been already trimmed and sanded.
 

g_boxwood

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This is how a brought the contact to the bulkhead.
 

g_boxwood

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Channels final sanded inside the airframe (glassine layer peeled off).
 

g_boxwood

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Channels epoxied, filleted and glassed to the airframe.
 

g_boxwood

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Dbag inside the airframe and between the channels; as You see the channels are only high enough to hold the BP can not to occlude the section too much.

I'm over for the moment, hope it will help...

Ciao,

Giacomo
 

g_boxwood

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I'm posting a sketch of the internal setup of the recovery components I made some time ago. It is quite rough but it should give you an idea of what the layout should look like.
 

g_boxwood

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A look into the airframe prior to pack everything inside; the red shock cord is the main's while the nomex sleeved one going inside and then out is the drogue's. One of the ends (actually the shortest one) is attached to the dbag as shown in the previous diagrams.
 
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