deployment Bag Help

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csoechtig

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I don't have any experience with Deployment Bags and need a little help. I've read all the threads and watched all the videos. They have been very helpful and have educated me on how to PACK the bag.

Interestingly enough, I can't find any threads, instructions, or videos on best practices for attaching the bag to the shock-cord/rocket. This is the one I'm using (Fruity Chutes)...

deployment_bag_600.jpg


I plan to use them with 96" and 120" cross fire parachutes. Any help would be appreciated. Pictures and/or video would be AWESOME!

Thanks,
Chris
 
I use the "free" bag system so all you would do would be to attach a drogue to the top of the bag so it will deploy the main chute. The nose cone would also be attached at this point.

The main parachute is attached to the recovery harness in the standard manner. I assume you are going to use quick links for all attachment points.

After deployment the rocket and the nose cone/deployment bag/drogue chute are not attached to each other.

If you want everything to come down together you would attach the long cord from the bag to the top of the parachute. A short recovery harness there may or may not be desirable depending on your situation.

Stay tuned for more answers.
 
Thanks Joe - -

So, you always have the nose cone come down under a separate chute? Ideally, I'd like to keep it all together. However, the Crossfire chutes by TopFLight don't have a connection point on the apex.

Any other options?
 
Typical "hook up" options shown well on this diagram courtesy of Giant Leap (TAC-Bag):

Giant Leap Diagram.jpg

There are many times I have sewn a TN loop onto an existing parachute. If you don't have a sewing machine or don't feel comfortable with your sewing skills, I'm sure you could send it back to Gary and he could do that mod for you.
 
I like the arrangement where all the recovery comes out the top rather than breaking the rocket in the middle. It is a bit different sort of setup and packs very well. It leaves room for long motors in the lower section.

The electronics bay is bolted to the lower section (or equivalent fairly solid attachment method) and the upper tube is solidly attached to the electronics bay. Only the nosecone comes off during flight.

The forward bulkhead of the electronics bay contains two attachment points (at least for larger rockets) and a single ejection charge canister or equivalent pressurization method. This is for deploying the drogue. The main is released by a tether of some form.

One of the attachment points on the electronics bay bulkhead is the main harness connection point. Then the harness or line is zig-zag folded neatly in the available space. Only enough line is needed to get the chute perhaps 6' past the upper end of the upper tube. More, or even less, can be used. It is not critical.

On top of this neatly stowed harness goes the D-bag with included chute. The part of the bag which would open to deploy the main goes downwards. The flap is held on by rubber bands cinching the harness along the side in a way which releases easily enough, allowing the harness itself to then open the D-bag flap. The whole bag assembly can slide freely in the upper tube but should not have a lot of free space on the sides. You want it nearly volume filling.

At the top of the D-bag there is a quick link connector attached. This link connects to two lines. One is the rather short bag hold-down line which goes down beside the bag and attaches to a tether, which then connects to the other attachment point on the ebay upper bulkhead. This line is attached under tension, compressing the bag down snugly against the main chute's recovery harness so it is immobile. The short link line needs to be heavy duty, as it will transfer the full drogue force.

The other attachment to the quick link at the top of the dbag is the drogue harness. This can be of whatever length you desire. I think I used about 20' for my 6" rocket. The length is not critical but should not be too short. At the other end of this line is the drogue of course. The harness for the drogue is stored neatly on top of the dbag, with the drogue stowed right on top the line.

There is also a short line connecting the nosecone to the drogue.

Beside all this is a section of small tubing (I used a 38mm liner section for a 6" rocket) which channels the ejection gasses from the ebay forward bulkhead charge well to along the side of the dbag and out to the top of the tube. So it is pressurized more at the top than the bottom so there is no tendency to try to blow the dbag out. It also helps keep everything pretty clean relative to more common methods.

With the upper tube properly sized, when the nosecone is put in place, a slight compression is required before pinning. There is no free space for stuff to move around under shock, vibe, and G loading. This in turn makes deployment very predictable.

There are details on some of this in https://www.rocketryforum.com/showthread.php?37382-Sprite-6-quot-and-a-baby-O The thread doesn't contain all the pictures one might want but should document a lot of this.

I learned this method from Jerry O'Sullivan and consider it one of the best ways to handle deployment for moderate sized rockets provided one feels free to bash the kit or to scratch build.

Gerald
 
Interestingly enough, I can't find any threads, instructions, or videos on best practices for attaching the bag to the shock-cord/rocket.

Chris, I'm glad you opened this thread. I've been looking at this site and others for a pretty long time now, and I don't remember any threads about the attachment of the bag either. I'm sure there have been, but I've missed them.

I was planning on opening a similar thread just to get opinions on how best to do this. As a TAP, I have to give advice to folks on how to do this, and the best I can give them is my experience. Chute fouling is the cause of many L3 failures, so I need to be a bit better educated.

In my stabilization project, I've had to try to come up with a reliable way to do this. The problem is that the stabilization section on the upper airframe is heavy relative to the fin can. So, the upper airframe & cone typically point straight down and the fin section flies at or above the drogue. So, it's easy to see the chute getting fouled by the upper airframe shortly after the main opens, or the fin section as the main rises. I've had a few close calls. Most of the flights in my stabilization testing include a back-facing camera on the nose cone, so I have some pretty good pictures of what things look like during deployment. I'd like to share my method and ask for feedback.

In my opinion, the purpose of the D bag is to organize the opening of the chute and also to delay the opening of the chute until the chute is above the remaining parts. I think the free bag method is pretty good, but it frees the chute early, where it can still get fouled, and also requires recovery of two separate parts. But, if you want to keep the cone attached, then you have to account for the problems it can cause. I have evolved to the setup shown in the first pic. The apogee event is conventional, with a zipperless coupler on the fin section and a drogue located 1/3 of the way between the sections (and closer to the fin section). For the main, there are two harnesses that join near the airframe. The idea is that when the main event occurs, the nose cone can go to the end of the harness without pulling on the D bag and opening the chute. Meanwhile, the D bag and pilot (in red) can travel upward relative to the remaining parts on a separate harness. It is easier for the small pilot to get past all of the parts then a large main, which is why I believe this approach improves reliability. Once the D bag/pilot harness is stretched out above the upper airframe, the chute gets pulled out of the bag. For the two harnesses associated with the main, I think the one to the D bag should be a bit shorter than the one to the nose cone.

I have two sequences that show how this works (one here and one in the next post). First pic just shows the configuration after apogee. The second shows the unopened D bag traveling up above the drogue and the other parts. The third shows the main opening once it rises to a harness length above the upper airframe.

Jim

Schematic.jpg

Pic 1.jpg

Pic 2.jpg

Pic 3.jpg
 
Here's the second sequence. First pic is again just of the rocket falling under drogue.

The second shows the D bag near the nose cone after the main event. The pilot chute on the D bag hasn't opened yet. I use a simple tube for the D bag (made by David Bachelder). The chute takes up about half of the volume of the bag, and then the bottom of the bag, like a flap, just folds over the top. I then use a couple of rubber bands to keep the bag contained. Tension on the harness later on will pull the bag open.

The third shows the D bag working its way past all of the other parts.

The fourth shows the D bag and pilot still rising - now well above everything else.

And the fifth shows the bag finally opening.

Jim

Pic 4.jpg

Pic 5.jpg

Pic 6.jpg

Pic 7.jpg

Pic 8.jpg
 
Of course what works for one doesn't necessarily work for everyone. I have FINALLY gotten a procedure which works for me.Attach shock cord to rocket and nosecone. Attach Dbag line to same attachment point on rocket. Attach main chute in a loop a third of the way down from nose. Attach pilot chute to nose. Stuff main chute into Dbag while its in rocket if you have the room, but not a deal breaker. This is how
I do it. My question to the thread, is why do you want to slow opening of main chute?
 
My question to the thread, is why do you want to slow opening of main chute?

Slow the opening is perhaps the wrong term. A better way to say it would be to open the main after it's above everything else.

I've seen a few L3 attempts and the main reason they fail is some issue with the main chute. People do the same thing on their L3 as their L1 and L2, except the chute is now much larger. The main typically comes out of the lowest part of the rocket, and then has to negotiate a path past all of the other parts. Because the main is large, it gets hung up more easily. Failed L3.

The point of the approach I listed is to let the chute rise with a much lower profile. When it opens, it's in clean air and the deployment from the bag is very orderly. The entire time required from the event to the point where the chute opens is only about 3 seconds, so not much of a delay. But in that time, most of the stuff that can hang up the chute is below the chute instead of above it.

Jim
 
Of course what works for one doesn't necessarily work for everyone. I have FINALLY gotten a procedure which works for me.Attach shock cord to rocket and nosecone. Attach Dbag line to same attachment point on rocket. Attach main chute in a loop a third of the way down from nose. Attach pilot chute to nose. Stuff main chute into Dbag while its in rocket if you have the room, but not a deal breaker. This is how
I do it. My question to the thread, is why do you want to slow opening of main chute?

As Jim said its not so much a slow opening as the D-bag allows the shroud lines to fully extend before the canopy opens, resulting in the initial shock being more evenly distributed to all the shroud lines at once and the canopy opening more evenly, helping to ensure the chute opens without tangling. If the canopy is fully inflated before the shroud lines are taught, the snap of the shroud lines tensioning adds additional stress to their attachment points and can weaken or damage the chute or shroud lines. It does also allow the chute to open in "clean air" without much chance of a rocket component hitting and collapsing it.
 
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I just did my L3 at LDRS using the Freebag system. (Nosecone chute pulling off the deployment bag and descending separately from the main) I have a deployment bag that allows everything to come down together as well which seems to be the more popular method but opted for the freebag instead to reduce the risk of tanglement. My Ultimate Darkstar used a 24 in. drogue, a Skyangle XL main packed in a freebag which was attached by a 10 ft. tether to a 48" TAC 1 attached to the nosecone. The nosecone chute & main descended one above the other and slightly side by side. It was a great view. The whole deployment sequence took 2.5 seconds. Thats why I programmed the altimeters to deploy the mains at 1000ft. With 40 ft. of nylon shock cord at both ends every c fold was taped at the ends to help absorb the cord tension during deployment. So the actual deployment where there was function was at 750 ft. But it went like a ballet the way it was controlled.
 
In my opinion, the purpose of the D bag is to organize the opening of the chute and also to delay the opening of the chute until the chute is above the remaining parts. I think the free bag method is pretty good, but it frees the chute early, where it can still get fouled, and also requires recovery of two separate parts.

Jim, this is a case where we are doing things differently. My free bag setup doesn't use a drogue. Ever. So, when the pilot chute comes out it slows the decent rate of the bag in relationship to the speed of the rest of the rocket so that it is a very short time before the rest of the rocket is below and clear of the d bag and chute. My recovery harnesses are very long and are looped into the stays in the bag just like the shroud lines. By design all of this leaves the bag before the chute does. Almost all of my deployments are around 500'. One reason is because they don't drift as far and I have never had a chute that didn't open if the charge goes off when it's supposed to. Another reason is that I like to watch the deployment up close. In most cases the chute is well away from the rest of the rocket when it begins to fill. I tried a drogue chute early on in my adventures in dual deployment and got tangles the first two times. Probably just the different way we set things up like Jim S. said.

Also at 500' I have never had to walk more than a couple of hundred feet to recover the nose cone and bag.

Good thread. Thanks for all the input from everyone. I'm writing it down.
 
Jim, this is a case where we are doing things differently. My free bag setup doesn't use a drogue. Ever. So, when the pilot chute comes out it slows the decent rate of the bag in relationship to the speed of the rest of the rocket so that it is a very short time before the rest of the rocket is below and clear of the d bag and chute. My recovery harnesses are very long and are looped into the stays in the bag just like the shroud lines. By design all of this leaves the bag before the chute does. Almost all of my deployments are around 500'. One reason is because they don't drift as far and I have never had a chute that didn't open if the charge goes off when it's supposed to. Another reason is that I like to watch the deployment up close. In most cases the chute is well away from the rest of the rocket when it begins to fill. I tried a drogue chute early on in my adventures in dual deployment and got tangles the first two times. Probably just the different way we set things up like Jim S. said.

Also at 500' I have never had to walk more than a couple of hundred feet to recover the nose cone and bag.

Good thread. Thanks for all the input from everyone. I'm writing it down.

Joe, I don't understand what you're saying about your configuration. I'd like to. Would it be possible to do a sketch?

Jim
 
I appreciate you starting this thread. I just recently got a Rocketman chute and had been curious as to how to set up a deployment bag.


Braden
 
I probably didn't explain it very well. You really don't want me to sketch something. ;) The major difference from a standard DD is that I do not use a drogue at apogee. That way, when the pilot chute comes out, the rest of the rocket clears the bag quickly because it is falling faster than it would with a drogue. At least that how it seems to work for me.

Meanwhile, at the main event the pilot chute is attached only to the bag and the nose cone. So in my mind that is three less items to get tangled in the recovery system since they are on their own. In my set up the recovery harness and the shroud lines deploy before the chute leaves the bag. The chute is the last thing out of the bag. I have a lot of DD flights and there have been issues from time to time but never a tangle with a free bag unless I was using a drogue. Your mileage my vary.

I use the Sky Angle type of D bags. Their explanation may be clearer than mine.

Thanks,
 
Jim, this is a case where we are doing things differently.

OK, I understand. Actually, the method I listed and yours have some similarities. In my approach, the pilot and bag are moving up relative to the rest of the rocket, but the cone is elsewhere on its own harness (and hopefully out of the way by design). In your approach, the pilot chute is larger because it has to bring down the cone, but the pilot/cone/bag still rise with the chute opening delayed a bit. And, the parts have to be brought down separately. Another way to look at it is that my approach is how your approach might be modified if you want to keep the cone connected.

Musing a bit more, if the drogue is properly sized such that things fall properly (invented V), then the free bag method should be more reliable (avoiding my extra nose cone harness). However, if things aren't falling well, which is the problem I had with my top-heavy stabilization rocket, then the smaller pilot might be an advantage. I think I should be working with my L3 candidates to get the drogue sized correctly and then use the free bag method if they want the best chance of a good deployment. I saw Stu Barrett do a flight like that a few years back. The rocket flew perfectly on drogue, best I've ever seen, and then the main deployment was perfect too. He couldn't find the cone though. Oh well.

Musing still more, the free bag method isn't very good for me for flights at Blackrock. My tracking electronics are in the nose cone (carbon airframes) and I typically deploy the main at 4,000+ feet in case I'm over a mountain (which has happened twice). A separate nose cone just doesn't fit the plan.

Jim
 
Agree Jim,

I am currently working on a project that will push the limits of my experience and will likely be modifying my system to be more like yours in having all parts attached. I had one instance of a 10,000' main deployment due to both apogee events going off at exactly the same time (yes folks, it can happen) and making my two 4 gram charges into one 8 gram charge and probably breaking the shear pins as the harness reached its limit rather abruptly. The deployment was fine but at 10,000' the distance between the rocket and the unattached nose cone/pilot chute/d-bag was significant. Thank goodness my GPS was not in the nosecone. Nosecone and bag are still missing.

It is important to find the correct size drogue if you are going to use one. My first time flying drogueless worked out great and has continued to serve me well in many, many DD flights over the last 10 years or more since I have become more active again thanks to retirement.
 
Chris,

After a lot of ground testing main chute deployment with the Sky Angle B2 deployment bag, which is a little different than the Fruity bag (long strap attached to the outside not inside), I found that attaching the long strap about 5' form the bottom of a 25' shock cord and the main chute to the end of the shock cord, allows the chute to be pulled complete free of the bag and NC. I attach the NC about 5' from the end of the shock cord, which allows all the roc components to hang straight down under the main chute during descent.
From hard experience, don't attach the D-bag to the hard point closest to the deployment charge. You want the bag to be quickly clear of the cargo bay. Suggest you do some ground testing before you launch to make sure your pulling the chute clear of the D-bag. You may need to adjust the length of the shock cord.

Clear skies and light winds...
Leo
 
There are many times I have sewn a TN loop onto an existing parachute. If you don't have a sewing machine or don't feel comfortable with your sewing skills, I'm sure you could send it back to Gary and he could do that mod for you.

If you haven't ordered your chutes yet ask Gary to sew a loop onto the chute apex for a bag deploy attachment. I want to do bag deploy in the future and I've talk to him about it and he said he could do it.
 
Awesome feedback everybody - thanks!

I believe I will go with the Free Bag method for a launch planned on July 18th. It's a +/-35lb rocket with a fairly heavy nose cone. So, it probably makes the most sense anyway.

In the future, I'm going to experiment with some of the other techniques shared in this thread. I believe this is what Spicer 007 was describing. It seems logical that as the nose cone is thrust forward the shock cord will straighten out and pull the chute from the bag. Agreed?

deploy20bag20example.jpg
 
I would consider that a very risky way of doing it. You are relying on momentum or random motion on the way down to effect extraction of the main from the dbag. This is going to result in unpredictable deployment at best.

If you are freebagging it, you need a chute on the nosecone sufficient to drop the descent rate of the nosecone to whatever velocity you choose.

Upon deployment, that chute will automatically cause the nosecone to end up above the rest of the rocket as it has a much lower descent rate. This tugs on the dbag, straightening the lines, and then deploying the main.

Gerald
 
I would consider that a very risky way of doing it. You are relying on momentum or random motion on the way down to effect extraction of the main from the dbag. This is going to result in unpredictable deployment at best.

If you are freebagging it, you need a chute on the nosecone sufficient to drop the descent rate of the nosecone to whatever velocity you choose.

Upon deployment, that chute will automatically cause the nosecone to end up above the rest of the rocket as it has a much lower descent rate. This tugs on the dbag, straightening the lines, and then deploying the main.

Gerald
With the free bag example from Dixon's post, the nose cone chute would do exactly what you described. That's my plan for July.

I might have misinterpreted Leo's description that ended up on my sketch. I can definitely see the risks and will experiment with different configurations via ground tests.

Thanks for all the feedback.
 
I agree with G. T.

It looks like the first thing to exit the bag is your chute. Very often, at least in my experience, the main charge goes off while the tube is pointing down. That means the chute is deploying while it has to make it all the way back to the top without tangling with anything. Not a risk I would take.

Also, in a dual deployment recovery system when you are using a drogue and a deployment bag you are going to need three chutes. The drogue (small usually) at apogee and you also need a pilot chute (small) attached to the deployment bag to ensure that the recovery harness, the shroud lines, and lastly the main chute do get out of the bag.

Don't depend on the nose cone to pull things out of the bag because once the energy from the ejection charge is expended everything is falling at basically the same rate.
 
Chris:

You have the same deployment bag setup as I do.

The long strap sticking out of the opening of the bag connects to the apex of your main chute. The lines of the chute are reefed through the white straps to slow the deployment and keep the lines organized. The small loop at the bottom of your bag connects to your pilot chute.

Here's my setup:

Here you can see the pilot chute is open. The lines of the main chute are extended out, and getting ready to pull the bag from the chute.

Launch9.jpg


Here you can see that the pilot chute has pulled the bag off of the main chute, and the main is just starting to open:

Launch10.jpg


Here the main has opened. You can see the deployment bag between the pilot chute and the main chute. My drogue snagged my nosecone, so it looks like a mess, but it was good.

Launch11.jpg


The recovery harness from the rocket connects to the ends of the main chute lines, as well as a shock cord going to the nosecone.
 
Excellent pictures! I hope people post more like these.

Your setup is basically what I was using in my initial stabilization flights where I was having problems. The problem I had was that with a heavy nose cone (actually, the cone and stabilization spool), it was pulling the chute out of the bag too early - roughly about the time of your first picture - and then the chute was getting tangled as it rose. You have a light cone and maybe avoid this issue?

Jim
 
Excellent pictures! I hope people post more like these.

Your setup is basically what I was using in my initial stabilization flights where I was having problems. The problem I had was that with a heavy nose cone (actually, the cone and stabilization spool), it was pulling the chute out of the bag too early - roughly about the time of your first picture - and then the chute was getting tangled as it rose. You have a light cone and maybe avoid this issue?

Jim

My nose cone isn't terribly heavy (572 g / 20.2 oz). How big is your pilot chute? You may want to try a slightly smaller pilot so that it doesn't pull the bag off as quick.
 
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