What size deployment bag should I get?
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rharshberger
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Did the chute come packed in a bag? (I am guessing not) Whatever D-bag you get should be an easy sliding fit inside the airframe but not sloppy loose, I have my wife make mine so that with the chute loaded the whole bag and flap has about a 1/4" gap around the circumference. One method that may work for you is to fold the chute as though you were not using a D-bag and see how large the bundle is then buy the nearest or next size up D-bag. What method are you using to pull the D-bag off the chute, Freebag and nosecone with pilot chute (separate nose cone recovery), a AARD or Tinder Descender with a Pilot chute on the bag etc. I am no expert as I am currently 3 for 3 on my D-bag based deployments using a D-bagged main with a pilot chute tethered to the nose cone and D-bag (nose cone and airframe are still connect via the normal recovery harness, however I attach the Main chute to a 3rd loop of the primary recovery harness just above the airframe opening).
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Lowpuller
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Round canopies are better suited for a diaper versus a D bag in my opinion. D bags are better suited for ram air canopies. In any case you want to ensure you have line stretch before the canopy is allowed to inflate. A diaper contains the skirt until the lines are tensioned. This results in much less opening force.
https://silverparachutes.com/app/download/6404237204/askal_jan2011.pdf
https://silverparachutes.com/app/download/6404237204/askal_jan2011.pdf
Chute did come with a bag, but it is very small and has no exterior bands for stowing the shrouds lines. It is just a bag with a loop on top. It would probably fit well in a 5" airframe.
I am not planning to s separate chute for the NC; just one main chute, no pilot. My first thought was to stick with what I know, which is to wrap it in a Nomex blanket and be done with it. However, I figured this is as good a time as any to try something new.
I looked at bags at Rocketman and Fruity Chutes, but Fruity Chutes only go up to a 7.5" airframe, and my rocket is an 8". Rocketman's specify the size of the chute, and that creates two problems: 1) he probably means Rocketman chutes, and 2) my chute is 15', and he skips from 14' to 16'!
Also, there is the GLR TAC C bag, and Rocketwoman, but hers only go up to 12'.
Hmm, where does one get a diaper, and is there any better documentation? That was a little hard to follow.
Just my 2 cents but if you are going to use a D-bag, I would highly recommend a pilot chute. Gene at Fruity Chutes was very helpful in putting together my set-up
rharshberger
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+1, the pilot chute is what strips the D-bag off the main reliably.
Lowpuller
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Lots of great diaper documentation, check out Dan Poynter, Parachute Manual, Volumes 1&2, mostly Volume 1 for rounds.
Usually the diaper is fixed to the parachute hem. It contains the hem by holding the diaper closed with rubber bands that are used to stow the lines. The lines have to deploy and reach line stretch before the hem can open allowing the parachute to inflate. Typically a pilot chute is attached to the apex to insure proper deployment sequence.
Usually the diaper is fixed to the parachute hem. It contains the hem by holding the diaper closed with rubber bands that are used to stow the lines. The lines have to deploy and reach line stretch before the hem can open allowing the parachute to inflate. Typically a pilot chute is attached to the apex to insure proper deployment sequence.
I would +2 this, Gene is a good resource to help you determine the size and configuration for a d-bag.
I also read the pdf and even with the pic you just provided I am still a bit unclear. I would be interested in reading, seeing any more information you may have on this. It looks interesting.
Lowpuller
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The picture above is the parachute stretched tight, top to bottom. The canopy is flaked to remove materials between the lines and then folded into 5ths which creates the long red tube you see with lines at the bottom. The lines are then gathered and folded up towards the canopy just enough to allow the diaper, which is seen to the hem, to wrap around the lines and the hem, holding the canopy "closed".
The diaper is basically a small square piece of cloth with two rubber bands on one side, and two grommets on the other. The diaper is wrapped around the hem and a short portion of the lines and held closed by pulling the rubber bands through the grommets. The remaining lines are then stowed in the rubber bands that lock the diaper closed. The remaining lines are stowed on the side of the diaper just like a D-bag
The diaper is basically a small square piece of cloth with two rubber bands on one side, and two grommets on the other. The diaper is wrapped around the hem and a short portion of the lines and held closed by pulling the rubber bands through the grommets. The remaining lines are then stowed in the rubber bands that lock the diaper closed. The remaining lines are stowed on the side of the diaper just like a D-bag
Lowpuller
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Frankly I don't think this matters much at apogee, hence the many Estes plastic parachutes that have survived, basically not much speed at opening. Dual deploy on the other hand, I imagine this is where a lot of parachutes fail.
Unless you are doing very large rockets the techniques for skydiving may not translate well to rocketry. In skydiving you have the weight of a person traveling at 120 miles per hour. You throw nylon out into that wind and there is more then enough force to deploy it correctly. A lightweight rocket (especially compared to a human) at apogee (hopefully traveling slowly as it peaks) may not apply enough force to get a full line stretch and normal deployment.
I am happy with a regular D-Bag. What I really don't know is if it is okay to use a bag sized for a 7.5" airframe, or should I try to get something for an 8" airframe, and if the latter, who sells them?
Thanks.
Thanks.
I am happy with a regular D-Bag. What I really don't know is if it is okay to use a bag sized for a 7.5" airframe, or should I try to get something for an 8" airframe, and if the latter, who sells them?
Thanks.
Thanks.
Gene will probably even make you a custome one but he is the man when it comes to D-bags!
Fruity Chutes
Fruity Chutes
rharshberger
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Personally that size D-bag would be fine for me as it should slide in and out straight without trying to cock, of course the pilot chute will extract the package.
John,
I assume this is for the Formula 200. I am using am 18' rocketman chute in mine and the D-Bag is going to be a 7.5" x 14" dbag from Fruity Chutes. Your 15' chute is small enough for the 10" dbag. I highly recommend them and if you give Gene a call he can confirm your sizing. Is your formula 200 configured for the standard DD setup?
I assume this is for the Formula 200. I am using am 18' rocketman chute in mine and the D-Bag is going to be a 7.5" x 14" dbag from Fruity Chutes. Your 15' chute is small enough for the 10" dbag. I highly recommend them and if you give Gene a call he can confirm your sizing. Is your formula 200 configured for the standard DD setup?
That's the same thing I have on my Performer 150. With the 6" ID, I made a D-bag with a 5" OD and elastic straps on it to hold the shroud lines. The chute goes in the bag and the lines are zig zagged into the elastic loops similar to the previous pics of a diaper. I sized my main to drop the rocket (-minus nose cone) at about 17 ft/sec. I made a pilot chute that would drop the nose cone at about 12 - 14 ft/second. I feel that is key to the design.
The pilot chute is attached to the nose cone and the top of the D-bag. Inside the debag is about 100 ft of 150 lb Dacron line connecting the D-bag to the top of the main chute.
When the main deployment charge goes off, it pushes the nose cone off and that pulls the pilot chute out. Since the rocket is falling at about 75 ft/sec under drogue, the pilot easily pulls the D-bag out of the payload. The shroud lines are then pulled out of the elastic on the D-bag. By the time that happens, the pilot chute and nose cone are well above the falling rocket and the main is being pulled straight upward above the rest of the rocket. The main comes out of the D-bag next and inflates. The nose cone and pilot stay attached to the main by the 100 ft of Dacron, but because they have a slightly slower decent rate, they stay above the main chute the whole way down.
This set up allows the pilot/nose cone to control the sequence of the main deployment, but the 100 ft of Dacron ensures the chutes come down together and the pilot and nose cone can't drift off into never never land.
I've had 4 flights so far and deployed the main at 1000 ft. each time. During the last flight I heard someone in the crowd comment that it had deployed way too high. I agree and since it has worked so well and so consistently on every flight, the deployment setting will be lowered to about 600 ft from now on.
That setup is working great for me so it's my suggestion.
If not over the weight limit SkyAngle XL bag fits snugly in my 6" IRIS.
THE XXL bag fits in my 9" Patriot with plenty of room.
Lowpuller
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The purpose of the bag is to ensure proper deployment sequence so you minimize malfunctions. You want the bag sized to the canopy so it is properly contained and deployed.
You could likely sew foam on to the d-bag in right location if you want to contain it in a certain location in the tube.
You could likely sew foam on to the d-bag in right location if you want to contain it in a certain location in the tube.
Always size to the chute. If the runs a little big for the chute that's not necessarily a problem though too small is. When you pack it, if it's sized just right the chute should seem to want to pop it's end out. In fact, after you pack it if you test it 2-3 good shakes should cause the entire chute to fall out.
7.5" size from Gene is perfect for the 8" formula 200 airframe. It won't be an issue. You can use smaller if you need too.
The launch date for my Formula 200 is either Dec or Jan. I can go over packing and setup of the d-bag with you then if you have any questions. As mentioned by handeman above, the deployment bag is very efficient at deploying a parachute fully in a very short timespan. You saw how quickly the main on my L2 came out of the d-bag and fully inflated. 600' or 500' main deployment is preferably here just because you don't have to worry about it not inflating right away.
Crazyrocket
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Not to derail the thread, but based on your experience, what is the minimum diameter rocket once should consider for a deployment bag. I would like to learn this technique, but my largest rocket is 4" diameter.
Friuty Chutes sell them for rockets as small as 3" airframes.
I'm not an expert in this but I have started using bags lately. Much better deployment.
As for sizing, my thoughts are diameter just smaller than the airframe, and sized long enough to contain the chute as well. So both measurements need consideration.
4" and 3" work fine. My Level 2 was a 4" airframe with a 4" bag. In general, I would frame the question as "what is the minimum parachute size I should consider using a deployment bag with?". The deployment bag should really be pulled off with a pilot chute. Once you drop below a certain size parachute this becomes more of a hindrance. Personally, I would say 24" main chutes are probably the starting point for when a d-bag would do some good.
I think that that 54mm will work well if you can get a bag sized for it. One thing you'll find is the d-bag packed chute ends up being much smaller than an equivalent burrito wrap because of the packing. I can fit a 60" chute into a dbag sized for a 3" airframe that is 6" long.
