Pilot Chute vs Streamer

[Keith Medlkock]

We just finished building our first kit rocket after getting tired of scratch building. Its an Aerotech G-Gorce, and was sooooo much easier and cheaper than scratch building. The only thing we changed was the recovery. We didnt want to deploy at apogee or want the added complexity of dual deployment electronics to get it landing closer.

Therefore, we'll use longer delays and deploy at high velocity, about 70mph according to simulations. I sewed up a deployment bag, but my question has to do with the extraction method. It's not a free bag and will be sewn to the main chute crown, but I don't know if I should use a pilot chute or just a streamer to get line stretch. Do any of you experienced guys have advice on which one is best?

 

[Woody's Workshop]

I see your a new member, Welcome to the Forum!
Not sure I'm getting this right, but here goes.
You are deploying the main chute at high speed.
You want to know how to implement a shock absorbing system on deployment.
If so, I think you are venturing into something that is avoided.
Ripping loose your recovery system or zippering the BT is the main reasons.

 

[Bat-mite]

Look into getting a Jolly Logic Chute Release. Deployee at apogee and don't inflate the chute until your preset altitude on descent. There are also cable-cutters and tethers that do the same thing, but the JLCR uses no pyrotechnics and works like a charm.

 

[ttabbal]

Assuming the rest of the system holds up, you're begging for a zipper without much gain. With a very late delay, you might save, what, 500ft altitude? If you insist on doing it, make sure to declare a heads up flight if it's an organized launch. And I suspect the streamer would be more likely to work without self-destructing.

If you really want to do dual-deploy with motor eject, use a chute release and a properly timed delay.

 

[Keith Medlkock]

I see your a new member, Welcome to the Forum!
Not sure I'm getting this right, but here goes.
You are deploying the main chute at high speed.
You want to know how to implement a shock absorbing system on deployment.
If so, I think you are venturing into something that is avoided.
Ripping loose your recovery system or zippering the BT is the main reasons.

Thanks. I've been here since 2013, but don't post much. There's no shock in this type of system so no need for shock absorption. Basically, the mass slows down gradually during a controlled/delayed deployment, rather than dumping a parachute to open immediately. It may take as much as 800ft to fully deploy, eliminating the need for dual deployment complexities or chasing the rocket after an apogee deployment.

I'm very experienced in this system, but never on a hobby rocket. Anyone with experience that's used a streamer and pilot chute, which one is best in this situation?

For everyone else, I'll draw up a diagram in a bit so maybe you can visualize it better. Thanks.

 

[Keith Medlkock]

Look into getting a Jolly Logic Chute Release. Deployee at apogee and don't inflate the chute until your preset altitude on descent. There are also cable-cutters and tethers that do the same thing, but the JLCR uses no pyrotechnics and works like a charm.

Thanks. I'm specifically avoiding electronics or dual deployment. A long delay will fire on the way down to trigger deployment at about 70mph. A pilot or streamer will stretch the lines while gradually slowing the rocket. After the last bight of line pulls free of the last locking stow, the deployment bag will open and allow the parachute out. Finally, the parachute will have a slider to slow its opening. It's just a typical skydiver setup, but I'm adapting it to the model rocket.

 

[Keith Medlkock]

Assuming the rest of the system holds up, you're begging for a zipper without much gain. With a very late delay, you might save, what, 500ft altitude? If you insist on doing it, make sure to declare a heads up flight if it's an organized launch. And I suspect the streamer would be more likely to work without self-destructing.

If you really want to do dual-deploy with motor eject, use a chute release and a properly timed delay.

Yes, I'm hoping to save around 500 ft. It should be just as reliable as the dual deploy if not more. I'll be throwing it out the sun roof plenty of times to fine tune the slider before it ever sees a launch.

 

[NateLowrie]

Thanks. I'm specifically avoiding electronics or dual deployment. A long delay will fire on the way down to trigger deployment at about 70mph. A pilot or streamer will stretch the lines while gradually slowing the rocket. After the last bight of line pulls free of the last locking stow, the deployment bag will open and allow the parachute out. Finally, the parachute will have a slider to slow its opening. It's just a typical skydiver setup, but I'm adapting it to the model rocket.

It should be fine. I wouldn't be worried about it especially with the slider. That is about the typical speed of a drougless main deployment.

How big is the main and how much does the fin can weigh?

 

[Keith Medlkock]

It should be fine. I wouldn't be worried about it especially with the slider. That is about the typical speed of a drougless main deployment.

How big is the main and how much does the fin can weigh?

The main is just the 42" flat that came with it. Fin can is 22.7oz without motor, and still needs a couple coats of paint. I'm thinking about using the nose as a pilot now, but hope someone who's actually done this will chime in. I'll get it with enough tailgate tests, but someone more experienced will save me TONS of trial and error.

 

[ksaves2]

Simulations are nice but one can't count on them for nothing more than a sketch. If you are off, you're looking at a zipper. I see the G-force is a cardboard rocket so the risk is pretty high if you don't hit your numbers dead on.
If one has a spiral wound fiberglass tube and a stout harness, not as much of a problem.
I've done a late delay with a small Wildman Jart with a 29mm motor though not on purpose. Strong harness and was no issue. You can try braiding/daisy chaining your chute lines: https://www.youtube.co/watch?v=RsKOciPYPA
and/or the single masking tape wrap of the harness to try to relieve the strain on deployment.
Other issue is if the nosecone comes off in a ballistic dive too late, it can fly up and smack the
sustainer tube or crack a fin.
If you haven't painted yet, you could put a single wrap of 1 or 2 oz. fiberglass cloth and laminating epoxy at the open end of the sustainer to strengthen up the tube if the deployment is off profile. Otherwise............ I wouldn't try to do a spectacular paint job on it to avoid against zippering on your first flight. Murphy's law is not on your side so it's best not to put a lot of effort to make it "too pretty". If it flies the way you want, then make it look good! Kurt

 

[Keith Medlkock]

Simulations are nice but one can't count on them for nothing more than a sketch. If you are off, you're looking at a zipper. I see the G-force is a cardboard rocket so the risk is pretty high if you don't hit your numbers dead on.
If one has a spiral wound fiberglass tube and a stout harness, not as much of a problem.
I've done a late delay with a small Wildman Jart with a 29mm motor though not on purpose. Strong harness and was no issue. You can try braiding/daisy chaining your chute lines: https://www.youtube.co/watch?v=RsKOciPYPA
and/or the single masking tape wrap of the harness to try to relieve the strain on deployment.
Other issue is if the nosecone comes off in a ballistic dive too late, it can fly up and smack the
sustainer tube or crack a fin.
If you haven't painted yet, you could put a single wrap of 1 or 2 oz. fiberglass cloth and laminating epoxy at the open end of the sustainer to strengthen up the tube if the deployment is off profile. Otherwise............ I wouldn't try to do a spectacular paint job on it to avoid against zippering on your first flight. Murphy's law is not on your side so it's best not to put a lot of effort to make it "too pretty". If it flies the way you want, then make it look good! Kurt

Good point about the nose hitting sustainer. I've only primered, so not too late for a little fiberglass. Study up on sliders. You can get a parachute to open as soft as you want. It's predictable and repeatable. We (hobby skydivers/wing suit pilots) dump our main canopies at 120mph without crushing our spines. Same principle applies to rocketry. If I can get the main to open over the span of 400-800ft, that's a soft opening in anyone's book. Don't knock it until you understand the principles. :wink:

Also, deployment bags are much better than daisy chained lines. The daisy chain pulling apart under speed generates heat that damages the lines. I wouldn't recommend it for longevity's sake.

 

[Keith Medlkock]

Added four more stowes to the bag...

 

[markkoelsch]

I hate to argue, but if you fly it this way you zipper the tube. Take the advice others have offered. Either pop at the top or go with a chute release.

 

[Keith Medlkock]

I hate to argue, but if you fly it this way you zipper the tube. Take the advice others have offered. Either pop at the top or go with a chute release.

I'm just looking for a specific answer to a specific question. I'm aware of the tried and true conventional wisdom here and very well may zipper the tube. I'll certainly report back if that happens. No pride on my end.:wink: I'm also going to go ahead and fiberglass reinforce the tube ends just in case.

However, it seems I have quite a bit of knowledge in parachute systems that most of you guys lack. The learning can go both ways, and while I certainly welcome unsolicited advice, at least have a knowledge base in my methods so you can point out the flaws. Come on, this is a hobby. You guys don't experiment with unconventional methods just for fun?

Apologies sir the semi rant. I'm just frustrated and for once would like to see my thread full of answers instead of endless replies telling me not to do exactly what I want to do, but I absolutely do appreciate the help, even unsolicited. Just takes lots of time responding to all the nay sayers trying not to come off as rude for ignoring someone.

 

[dhbarr]

I don't have practical experience with chute vs streamer for debagging, but the number of times I've seen a streamer tangle in a line would make me want to stick with something compact and foolproof.

Something like a a squirrel.ws snatch, downscaled. Half toroid, half balute, all pilot.

 

[markkoelsch]

I take no offense. The rocket will fall fast. The chute and bag come out. The rocket is still hauling. The bag comes off and chute inflates in a controlled manner- the rocket is still hauling butt. The rocket, moving much faster than the chute, runs into the cord, which slices through the tube.

Not arguing- just offering opinion based on 20 years of high power experience on top of 20 some years of low and mid power before that.

Good luck.

 

[Lowpuller]

I'm a skydiver and a parachute rigger, I totally get what your going for..................but I also believe you may face several potential issues.

You may not have enough force to deploy the canopy from the Dbag, the separated rocket will generate lots of drag.

And lastly your slider idea will work great, as a matter of fact so good, my guess is that you will snivel in.

Don't get me wrong I love your thinking, and on a bigger heavier rocket your right on track.

For this case I would recommend a Jolly Logic Chute Realease, awesome device and worth every penny.

 

[qquake2k]

I'll be honest. I have no idea what you're trying to do. But I'm very curious to see whether it works or not.

 

[conwayte]

Hello! I’m also a skydiver (off and on since ‘86--mostly off lately) and have had similar thoughts as to staging the deployment sequence.
My first thought is, I wouldn’t do any fiberglassing at this point--if you have everything properly staged and the slider is properly sized/configured, I think this has a better than average chance of working. If you fiberglass, you might not have evidence of that. Of course it could zipper, but then you’ll know.


To your original question--I would go with a pilot chute as opposed to a streamer. I wonder if attaching the pilot chute to the nose then a bridle down to the d-bag would keep everything lined up nicely? Modelrocketparachutes.com sells what they call the “Nylamesh” chute that looks similar to a skydiving pilot chute. You think their 15” Nylamesh would put everything in line and give you enough pull?


I think your d-bag looks good. Containing the parachute and line management are the name of the game there. One thing that might be worth a try for future attempts is to place your line stow points more outboard on the bag--I think this might allow for smaller end loops and less chance of one half-hitching over another. Heck, I’ll bet you could even do a tail pocket with one locking stow. Oh, geez, now I’m going to have to dust off my sewing machine…


As Lowpuller mentioned--the Jolly Logic Chute Release is a pretty cool little device. I have one and have flown it a few times with great success. I’ll bet one could figure out a way to combine it with a deployment bag.


As I have 0 high power experience to date (only flown F’s and G’s so far) my thoughts are only based on limited mid-power experience plus my skydiving knowledge.
Best of luck!

 

[dhkaiser]

Regards the “Nylamesh” chute, I have flown those on MPR and have found they do not open reliably. I have had everything from tangled chutes to delayed opening.

 

[Keith Medlkock]

I take no offense. The rocket will fall fast. The chute and bag come out. The rocket is still hauling. The bag comes off and chute inflates in a controlled manner- the rocket is still hauling butt. The rocket, moving much faster than the chute, runs into the cord, which slices through the tube.

Not arguing- just offering opinion based on 20 years of high power experience on top of 20 some years of low and mid power before that.

Good luck.

Thanks. Do you believe fiberglass reinforcing at the lips would solve the zipper issue?

 

[Keith Medlkock]

I'm a skydiver and a parachute rigger, I totally get what your going for..................but I also believe you may face several potential issues.

You may not have enough force to deploy the canopy from the Dbag, the separated rocket will generate lots of drag.

And lastly your slider idea will work great, as a matter of fact so good, my guess is that you will snivel in.

Don't get me wrong I love your thinking, and on a bigger heavier rocket your right on track.

For this case I would recommend a Jolly Logic Chute Realease, awesome device and worth every penny.

Thanks for the input. Your second point is exactly why I started thinking about using the nose as the pilot. It's way lighter than the booster and has more surface area.

 

[Keith Medlkock]

I'll be honest. I have no idea what you're trying to do. But I'm very curious to see whether it works or not.

Me too!:wink: Sucess or failure, I'll post an update.

 

[Keith Medlkock]

Hello! I’m also a skydiver (off and on since ‘86--mostly off lately) and have had similar thoughts as to staging the deployment sequence.
My first thought is, I wouldn’t do any fiberglassing at this point--if you have everything properly staged and the slider is properly sized/configured, I think this has a better than average chance of working. If you fiberglass, you might not have evidence of that. Of course it could zipper, but then you’ll know.


To your original question--I would go with a pilot chute as opposed to a streamer. I wonder if attaching the pilot chute to the nose then a bridle down to the d-bag would keep everything lined up nicely? Modelrocketparachutes.com sells what they call the “Nylamesh” chute that looks similar to a skydiving pilot chute. You think their 15” Nylamesh would put everything in line and give you enough pull?


I think your d-bag looks good. Containing the parachute and line management are the name of the game there. One thing that might be worth a try for future attempts is to place your line stow points more outboard on the bag--I think this might allow for smaller end loops and less chance of one half-hitching over another. Heck, I’ll bet you could even do a tail pocket with one locking stow. Oh, geez, now I’m going to have to dust off my sewing machine…


As Lowpuller mentioned--the Jolly Logic Chute Release is a pretty cool little device. I have one and have flown it a few times with great success. I’ll bet one could figure out a way to combine it with a deployment bag.


As I have 0 high power experience to date (only flown F’s and G’s so far) my thoughts are only based on limited mid-power experience plus my skydiving knowledge.
Best of luck!

Thanks for the ideas! If you look closely at the d bag, the stowes are tiny rubber bands. It doesn't take much to break one, so hopefully it'll just snap off in the case of a lock up.

 

[conwayte]

Good point about the little rubber bands. I also like your idea about tailgate/sunroof testing.

 

[NateLowrie]

If I were sizing the pilot chute I would start at 12in. Anything larger and you risk the kind of snapback that causes a zipper.

I am really interested in how your method works out because this could actually be the perfect compliment to an ARRD deployment. I am curious how much better the opening will be compared to a fruity chutes Dbag which is what I am using.

 

[Keith Medlkock]

So, it seems the biggest concern is zippering. How do you guys feel about the anti-zipper harness described here?

https://www.apogeerockets.com/education/downloads/Newsletter282.pdf

 

[Keith Medlkock]

If I were sizing the pilot chute I would start at 12in. Anything larger and you risk the kind of snapback that causes a zipper.

I am really interested in how your method works out because this could actually be the perfect compliment to an ARRD deployment. I am curious how much better the opening will be compared to a fruity chutes Dbag which is what I am using.

Not my design, just copying any modern skydive rig. Google skydiving d bags to get a better idea.
There's only two significant difference between my d bag and the fruity chutes one that I can see.

1) Three locking stowes. The last three bights of line lock my bag closed. This makes sure the bag cannot open until all the lines are stretched out nice & straight.
2) Rubber bands instead of elastic. The fruity bags elastic looks like high quality strong stuff. If lines somehow get wrapped up on the elastic, it probably won't break and free the lines. The tiny sacrificial rubber bands on my bag hold the lines tight, but have a predictable breakage point. If I get a line lock, the rubber band will just break, freeing the lines.

Of course I have no idea if any of that translates to better or more reliable openings as it relates to rocketry, but that's the theory.

 

[ksaves2]

Not my design, just copying any modern skydive rig. Google skydiving d bags to get a better idea.
There's only two significant difference between my d bag and the fruity chutes one that I can see.

1) Three locking stowes. The last three bights of line lock my bag closed. This makes sure the bag cannot open until all the lines are stretched out nice & straight.
2) Rubber bands instead of elastic. The fruity bags elastic looks like high quality strong stuff. If lines somehow get wrapped up on the elastic, it probably won't break and free the lines. The tiny sacrificial rubber bands on my bag hold the lines tight, but have a predictable breakage point. If I get a line lock, the rubber band will just break, freeing the lines.

Of course I have no idea if any of that translates to better or more reliable openings as it relates to rocketry, but that's the theory.

As long as you're sure those bands will break when they are supposed to. Your rocket nose down is going to be picking up speed very quickly and your harness can still have the ability to slice through the cardboard in spite of your precautions. You could try to get an appropriate sized rubber ball you could thread on your harness to the spot on the open end of the
sustainer. It would spread the force over a larger area of the tube and perhaps save from a zipper. Your strategies would be more amenable to a fiberglass rocket that could handle
any "flier" error in estimation. I'd still strongly consider a fiberglass wrap on the open end of the sustainer. Good luck. Kurt

 

[Keith Medlkock]

As long as you're sure those bands will break when they are supposed to. Your rocket nose down is going to be picking up speed very quickly and your harness can still have the ability to slice through the cardboard in spite of your precautions. You could try to get an appropriate sized rubber ball you could thread on your harness to the spot on the open end of the
sustainer. It would spread the force over a larger area of the tube and perhaps save from a zipper. Your strategies would be more amenable to a fiberglass rocket that could handle
any "flier" error in estimation. I'd still strongly consider a fiberglass wrap on the open end of the sustainer. Good luck. Kurt

How do you feel about the zipperproof harness link I posted above? This is our first kit rocket. All others are scratch built fiberglass so these concerns are definitely new to me.