Who is using deployment bags and for what size chutes/rockets?

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jahall4

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I have never seen them used in person that I’m aware of. I don’t think even on some L3 rockets. I’d suspect there is a starting chute size at which it becomes important.
 
I have never seen them used in person that I’m aware of. I don’t think even on some L3 rockets. I’d suspect there is a starting chute size at which it becomes important.

Madcow Formula 200, 8" diam., 124" tall. 15' military silk chute, FruityChutes 10" D-bag.

I don't know that there is a starting chute size. A D-bag is a very efficient way of managing a chute. It also adds some complexity.

My take...

Advantages
  • Chute does not need to be folded, just stuff it in.
  • Entire chute is out of the rocket before shroud lines start to stretch.
  • Shroud lines are stretched before chute deploys.
  • Chute can be packed in bag at home and brought to launch, and can be moved from rocket to rocket.

Disadvantages
  • Adds a learning curve.
  • Extra pilot chute is required.
  • Pilot chute needs to be wrapped in Nomex, so it is not a Nomex-free design.
  • Cost of bag and pilot chute.
  • No real way to test deployment until it is in the air.
After my ground testing, I knew I could get my shear pins broken and my D-bag and pilot chute out of the payload bay. I had to trust that the pilot chute would provide sufficient resistance on the top of the bag as the nose cone fell groundward to pull the main out of the bag. This was a big area of apprehension. But it worked like a charm. Very happy with the method.

Video shows it pretty clearly. My only caveat is that I had my main set to 1000', and the apogee was at 1250', so the NC didn't have enough time to get stable before the main charge blew. That is why the harness seems to be inhibiting the chute a bit. On my previous two flights to higher altitudes, this did not happen.

[video=youtube;il9FiXM4bqE]https://www.youtube.com/watch?v=il9FiXM4bqE&t=9s[/video]

IMG_1897.jpg
 
I have been using deployment bags since my L1, first attempt :facepalm:

I was very interested in getting to know deployment bags when I first got into HPR so I experimented with using a bag on a 36" Fruity Chute Iris Ultra Compact in a 3" PML Bull Pup. I set it up using a modified deployment bag that had 2 grommets punched into it to pass a zip tie through which also held the pilot/drogue (Fruity Chute 15" Classic Elliptical) in place to be cut by a cable cutter. I also used my 4" Tomach, in my avatar, to experiment with a deployment bag but this was using a custom deployment bag holder against the bulkhead of the nosecone, held in place with an ARRD, which is what my pilot/drogue was held to.

Needless to say these experiments were interesting, educational and fun. Remarkably even though all deployments have a failure attached to them, both rockets survived pretty much unscathed.

Currently I only use a deployment bag in my 3" Darkstar. I use a 48" Fruity Chute Iris Ultra, with a 12" Fruity Chute Classic Elliptical pilot and a slider ring on the main chute. The slider is the latest edition, which helps to retard the inflation of the chute. I actually caught the slider in action on my last flight with my on-board camera.

All of this experience along with some yet to try techniques are for some bigger builds I have in the works. Although I would not say that a deployment bag is a waste of time on any rocket that it will safely fit into, which in my experience is about a 3" airframe. Having said that I would not be surprised if it has been used in smaller air frames.

If used correctly a deployment bag mitigates deployment issues by deploying your laundry in a consistent and reliable order, and it typically happens fast.

If you are interested in the technology I would contact Gene at Fruity Chutes, he has been very helpful in providing me good informed advice.
 
I use d-bags as the situation seems to require it. Certainly for any 6" or larger airframe as I think the d-bag helps in keeping everything in order. For my level 3 I used a SkyAngle Cert 3 XL chute with a d-bag. On a big rocket there is just so much more rigging that a d-bag helps keep it from getting tangled. I've done it as SkyAngle recommended where the nosecone and d-bag recover separately and also where all the parts stay together.

As Bat-mite says, it is more complex and requires careful planning and testing. I had mine rigged incorrectly the first time I tested it and found that I had to carefully write up how everything linked together. And I ended up wrapping up the whole thing (d-bag and pilot chute) in a large Nomex cloth to protect the pilot chute. That also provided a very neat bundle that slid into the airframe.

Ideally you should find someone with experience using that type of recovery and ask for their help. That's will save you a lot of time and help avoid costly mistakes.

Good luck,


Tony
 
Everyone great info. Big thanks especially to John for putting all the links and video together.

Where do I find some information about attaching the chute and bag to the harness, in particular the orientation of the bagged chute and how it all comes together in the airframe. Simple picture would do it.
 
Pretty simple. This is my way; others will vary. There is a loop on the top of the bag. Attach the pilot chute to that. Put a Nomex under it. Inside the bag there is a long tether. Attach that to the top of your main chute. Pilot chute pulls bag off of main chute, remains attached by the tether. Z-fold and stuff shroud lines in any orderly fashion under the elastic bands.

Main chute shroud lines attach to the nose cone. When the NC and D-bag come out of the payload tube, the NC starts falling down, but the pilot chute pulls the D-bag up. Shroud lines get systematically yanked out of the elastic, and the the chute falls out of the bag.

Final picture below:
D-bagDD.png
 
Pretty simple. This is my way; others will vary. There is a loop on the top of the bag. Attach the pilot chute to that. Put a Nomex under it. Inside the bag there is a long tether. Attach that to the top of your main chute. Pilot chute pulls bag off of main chute, remains attached by the tether. Z-fold and stuff shroud lines in any orderly fashion under the elastic bands.

Main chute shroud lines attach to the nose cone. When the NC and D-bag come out of the payload tube, the NC starts falling down, but the pilot chute pulls the D-bag up. Shroud lines get systematically yanked out of the elastic, and the the chute falls out of the bag.

Final picture below:
View attachment 335973

So how does that look inside the airframe?
 
To supplement John's answer.

[video=youtube;YvzI5QJftjI]https://www.youtube.com/watch?v=YvzI5QJftjI[/video]

[video=youtube;_0YHlspcqeU]https://www.youtube.com/watch?v=_0YHlspcqeU[/video]

[video=youtube;wGLu54LYfbo]https://www.youtube.com/watch?v=wGLu54LYfbo[/video]

And there are more on YouTube
 
To supplement John's answer.

[video=youtube;YvzI5QJftjI]https://www.youtube.com/watch?v=YvzI5QJftjI[/video]

[video=youtube;_0YHlspcqeU]https://www.youtube.com/watch?v=_0YHlspcqeU[/video]

[video=youtube;wGLu54LYfbo]https://www.youtube.com/watch?v=wGLu54LYfbo[/video]

And there are more on YouTube

I've seen all these and the don't show orientation of the bag in the airframe along with the harness and pilot chute.
 
...
I also used my 4" Tomach, in my avatar, to experiment with a deployment bag but this was using a custom deployment bag holder against the bulkhead of the nosecone
....

You sure that's not a Tembo? :wink: Sorry... couldn't help myself.

I really am following along trying to learn, not just here to bust your... well, you know. Been considering D-Bags for a while now. Pat at Dino Chutes has em for 2.5" and 3" rockets, which I have been wanting to try, just haven't yet.
 
Not going to ask you to do that. A drawing similar to John's would do it, but before ejection.

Honestly I have not touched my rockets in close to two months now due to work commitments, so mocking something up would be a treat. I will try to put it together this weekend.

Now having said that, from my observations, John (AKA Bat-might) and manixFan are completely correct in their comments about deployment bag strategies for larger air-frames. I have witnessed several of these strategies including what some refer to as the "free-bagging", which manixFan mentioned "I've done it as SkyAngle recommended where the nosecone and d-bag recover separately". This is essentially where the deployment bag tether is not connected to the top loop of the chute. It simply pulls free allowing the chute to go on it's merry way with typically the booster section, and the nosecone and or payload/nosecone to go off in another direction. In this case the pilot chute becomes the main for the free floating section/s.

Regardless of what technique you need to understand, seeing how things pack in even a basic strategy will help, so I will put something together to better understand this.

You sure that's not a Tembo? :wink: Sorry... couldn't help myself.

I really am following along trying to learn, not just here to bust your... well, you know. Been considering D-Bags for a while now. Pat at Dino Chutes has em for 2.5" and 3" rockets, which I have been wanting to try, just haven't yet.

lol and I hadn't even had a glass of wine when I posted that. My bad yes you are correct that is a 4" Tembo and it I used it as an experimental platform for a deployment bag and C02 ejection.
 
Thank Michael, knock yourself out! :)

It's looking more and more like my question about the configuration in the tube boils down to which direction the bag opening faces. Extremely basic but I would think very important! Yet no one has even mentioned that.
 
Thank Michael, knock yourself out! :)

It's looking more and more like my question about the configuration in the tube boils down to which direction the bag opening faces. Extremely basic but I would think very important! Yet no one has even mentioned that.
The bag opening faces the bottom of the rocket. Think of it as the bag being pulled off the chute - the chute is anchored to the body tube and the bag is anchored to the nose cone. The nose cone/drogue chute pull the lines out of the loops and off the parachute, so the bag opening should be facing the airframe.

text diagram: main shock cord, d-bag (open end first), pilot chute (with Nomex protector), top portion of shock cord, nose cone.

I use blue tape/and or rubber bands to help control the shock cord as I pack it. On a large rocket the weight and pull involved will easily break the tape. (But done very loosely and only one wrap. I've seen the N1 failure video.)

Another important point to keep in mind that deployment is slower with a d-bag so you need to take that into account when you set your main altitude. With my 6" and larger rockets I set it to at least 1500' so everything has plenty of time to work itself out.


Tony
 
It makes sense to face the opening down as long as a strap connects to the cute at the spill hole to the bag which in turn is attached to the pilot. For those that "free-bag", it would appear that setup is less dependable about getting the chute out.
 
It makes sense to face the opening down as long as a strap connects to the cute at the spill hole to the bag which in turn is attached to the pilot. For those that "free-bag", it would appear that setup is less dependable about getting the chute out.

Quite the opposite, iirc the free-bag method is the least prone to tangling of the d-bag systems. I use d-bags with elastic loops on the outside of the bag and I make sure my loops are snug but not tight on the shroud lines, by doing so the bag is actually being pulled clear of the airframe by the pilot chute and stretching the shroud lines out at the same time. Its possible for the bag to be stripped off the chute inside the airframe if the shrouds are not under some form of tension and if the bag is loose on the chute (like a slightly large bag). I prefer my chute pretty snug in the bag, the z-folding into the bag allows even a pretty snug packed bag to deploy properly.
 
Quite the opposite, iirc the free-bag method is the least prone to tangling of the d-bag systems. ... Its possible for the bag to be stripped off the chute...

If tangling is a much bigger concern than leaving the cute in the airframe then maybe, but that's not what I was talking about. The free-bag system may be less likely to tangle after deployment, but since the main chute is not attached to the pilot (via the bag) there is more chance you never get the main into the airstream, correct? With the Main attached to the pilot there is always a chance a "stuck" main, for whatever reason, could be pulled free before is goes splat :), right?

If I have to choose between a fouled/tangled main over a no main at all it seems most cautious to choose the prior. That's all I'm saying.
 
So I have seen the harness in the elastic. No issues with ejection gases or what not burning the elastic or harness? Or is the whole thing wrapped in nomex?

Seems to me the free bag method would work the best. That way the nose cone gets out of the way and there is less junk to get tangled. I would prefer to have all pieces attached and come down together though. Especially since the tracker is usually in the nose cone.

If tangling is a much bigger concern than leaving the cute in the airframe then maybe, but that's not what I was talking about. The free-bag system may be less likely to tangle after deployment, but since the main chute is not attached to the pilot (via the bag) there is more chance you never get the main into the airstream, correct? With the Main attached to the pilot there is always a chance a "stuck" main, for whatever reason, could be pulled free before is goes splat :), right?

If I have to choose between a fouled/tangled main over a no main at all it seems most cautious to choose the prior. That's all I'm saying.

Interesting. I see what you are saying. The nose cone pulls the bag clean off the chute and out of the air frame but the main is stubborn and just sits there. Like the table cloth trick.
 
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Has a bag been stripped off the chute inside the airframe before? Sure its happened, not to me yet, but I make sure that the bag has to be pulled off the chute not the chute falls out of the bag ( test by holding the bag open end down if the chute falls out its loose, possibly too loose, I guess you could use a break string between bag and chute, but I dont believe its necessary).
 
Free-bagging it, at best, appears to come down to more perfect recoveries vs safer recoveries. Does anyone have stats to support one over the other? Saying it happened to "Bob" one time is anecdotal. :)
 
From all the research I did the true free bag method - where the d-bag is attached to the nosecone and recovers separately - is the most reliable method. If you look at most d-bags there is a large flap that wraps around the bottom of the bag and then up over the shroud lines. So it would be very difficult to pull the bag off the chute as the flap isn't really free to release the chute until it's out of the body tube. So as long as there is a pilot chute on the nosecone once it's out in the airstream it should pull the chute out of body tube.

In all my testing never once was I able to pull the bag off the chute while it was still in the body tube.


Tony
 
From all the research I did the true free bag method - where the d-bag is attached to the nosecone and recovers separately - is the most reliable method

Yep, I can see how a properly sized and packed bag makes it nearly impossible to eject the bag w/o the chute, but I'm not convinced that outweighs the safety of always having the pilot attached.

What was the most common problem when a free bag was not used?
 
I use deployment bags for my 4" rockets, but I do it differently than most. I've posted this before, and I don't get a lot of love, but I don't know why not - this configuration has worked well for me and others. The problem I see with the conventional configuration is that the pilot, attached to the cone, doesn't open right away. This causes the cone to pull of the bag while the chute is still low relative to the other parts, and the chute is stretched horizontally or even downward. Think about how many times you have seen a chute open low and you wondered if it would get past the other parts without tangling. I had a particular problem with this when I was testing my stabilization system, which results in the upper air frame being relatively heavy. I could not get the upper air frame to "fly" on drogue, and the chute was typically blown more downward where it could tangle with the upper air frame when it opened.

So, I came up with something different, per the attached pic. The method uses a piston (which I always use in any case). Two harnesses come from the piston. One goes to the cone and the other to the deployment bag and pilot. Upon deployment, both harnesses get streched out to their length, but then the cone goes down and the bag/pilot go up. One thing to note here is that a piston is needed because the cone does not serve to pull out the chute as it normally would. So, the bag and pilot now rise relative to the other parts. Since the pilot is small relative to a main, it is less likely to get hung up with the other parts as it rises. Then, when the pilot pulls tension on the the upper air frame, the chute opens in a vertical configurtion, and is above all of the other parts. A few pics are attached that show this. They are from the perspective of the cone looking backward.

The packing order is piston, bag harness, bag, pilot chute, cone harness (z folded with blue tape), and cone. I use tubular deplolyment bags with the bag itself folded in two and held shut with a couple of rubber bands ( to keep the chute contained until you want it pulled out).

I am considering a modification to this where the cone would come down on its own chute, more like the free bag approach. This would eliminate the harness to the cone. The difference would be that the cone would not be attached to the bag and would not pull the bag off of the chute. Instead, the bag would rise on its pilot and open after it is above everything else.

Jim

Schematic.jpg

Pic 6.png

Pic 7.png

Pic 8.png

DSCF0139.jpg
 
The way I tested my setup was to pack everything in the body tube as I would for a flight. Then I had someone hold the tube while I grabbed the nosecone and took off running (well, maybe not running but moving at good clip). The tube was on a stand about a foot and a half off the ground. I could see how things were pulled out of the body tube and how they stretched out on the ground and finally how the d-bag was pulled off the chute.

The first time I did that I found that I had wrapped the whole assembly with a large Nomex blanket (I think it was 30") in a way that it interfered with the pilot chute. I moved the attachment of the blanket to much higher up on the shock cord so as things separated the blanket would get pulled off everything. It was also good practice to learn how to pack everything neatly.

To be honest, I think you are obsessing over the orientation a bit much. In the end I don't think it really matters as once out in the airstream the pilot chute/nosecone are going to pull everything out straight. So not matter which way you pack the d-bag it will flip around the correct way. However, if you think about the attachment point of the pilot chute/nose cone, it's at the top of the d-bag. To me that says you should have that end pointed up towards the nosecone.


Tony
 
The method uses ... Two harnesses come from the piston. One goes to the cone and the other to the deployment bag and pilot. Upon deployment, both harnesses get stretched out to their length, but then the cone goes down and the bag/pilot go up.

Interesting, makes sense. Variation of just attaching the chute to the harness down some from the cone. In you config down is all the way into the tube.
 
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