Foolproof (or almost foolproof) method of getting parachute to deploy fully and not tangled up?

[PatD]

That said, nothing is 100% foolproof.

If you make something 100% foolproof, they will make a better fool.

 

[bad_idea]

So far in my BAR-dom, I've been building minimum diameter 18 and 24mm rockets that fly well in my local park on small blackpowder motors. This quickly taught me how often ejection or deployment in these small tubes can fail, especially with in-tube shock cord mounts.

A conversation with @JimJarvis50 at a launch a few months back - and having watched his Narcon '21 presentation and Q&A six or seven times - convinced me to try pistons for ejection. Trifold and through-the-wall shock cord mounts won't work with a piston though, and being minimum diameter rockets, there's no engine mount to which to attach the shock cord.

My solution has been to place a bulkhead - perfroated with a number of holes for ejection gas to pass through - ahead of the engine and to thread the shock cord through the middle of it and thence through a small hole in the center of the piston. Being that it would be almost impossible to replace a shock cord attached this way - and that being directly exposed to the full blast of ejection, even kevlar wouldn't last long - I thread a stainless steel fishing leader through the bulkhead and piston. The leader runs out to about the end of the body tube, after which I attach some thin kevlar to allow the piston to travel all the way out of the tube if it feels like it. The way 40 lb. kevlar likes nothing better than to tie knots of itself has me now attaching some heavier, less tangly kevlar for the main portion of the shock cord once the piston is clear of the tube.

Hitherto I've launched with the flat side of the piston toward the front of the rocket and the "cup" facing the perforated bulkhead above the motor. Reading more about pistons, I'm finding some people having success when reversing the piston such that the cup faces towards the nose, and I'll be trying that configuration in a test flight soon. Not sure how well that orientation of the piston is going to work, but I can say that with the orientation I've flown with so far, I have 100% ejection success in ten or so flights since switching to pistons vs. 50% or less beforehand (partly due no doubt to my inexperience in chute packing; fortunately I mostly fly in a grass field). Not enough gas has leaked through the piston and around the steel leader to singe the chute or streamer either, so no recovery wadding or dog barf needed. The way the various elements of the shock cord are kept centered until after the piston has left the body has also so far protected against zippers, though the rockets have all been moving fairly slowly at ejection.

An experiment I've been meaning to try would be to vent the piston on the sides so that the pressure inside it drops sharply as it starts to leave the body tube, futher reducing the chance of the shock cord swinging to the side of the tube and zippering. That would require going back to "cup-rearward" orientation; the rocket I've been working on lately has a body tube long enough to experiment with either way. The biggest downside I've had so far is that friction fit has been relatively unreliable; it seems the pressure is high enough to blow the motor right out of the body unless I use enough tape to make extracting the spent motor without crumpling the body tube nearly impossible. For this reason I've gone to taping an external thrust ring about body diameter to the rear of the motor and then taping that ring to the rocket body. Not quite as streamlined (not that my rockets are very streamlined at all yet), but reliable so far.

On low altitude flights (1/2-A or A), I've had bigger chutes fail to open fully even after being blown well free of the rocket at ejection. Given the low altitudes, light rockets, and soft ground I've mostly flown on, I've switched to streamers on all the light rockets.

Small sample size of flights, but so far this has been as close to foolproof as I've been able to get.

(Apologies for the long post, but as the saying goes, I don't have the time today to write a shorter one.)

 

[Ronz Rocketz]

I've been using 10' on my BT-60 size rockets. Maybe 8' would work just as well. I also built a spool to roll up the cord and it has worked perfectly in my tests. I've watched the crochet method several times and haven't caught on to it. I also know people who use the figure 8 method and say it works well for them.

Any foolproof sources of cheap spools (probably 3D printed) that will work in a BT60? I'd be willing to try one as long as it works.

Any tips on preventing shroud lines from tangling with shock cord are appreciated! That happens a lot to me.
A lot of the time, for my LPR rockets, even with tangled shroud lines and shock cords, the tangled parachute, shock cord, and shroud lines just act like a big streamer and slow down the rocket enough that it lands unharmed or only slightly damaged. Got me to thinking (uh oh). In just how big/heavy of a rocket could I reasonably use a streamer as the recovery device? How big of a streamer? Two streamers? Streamers are so much easier to use than parachutes.

Like I said, every time I find a technique that seems to work, it fails on my eventually. We had our share of failures yesterday. Nothing lost or horribly damaged so another awesome day in the field...

Or use a piece of kevlar tied to centering ring or tube coupler if you can get it to go far enough down the body tube?

Do you mean like the Qualman baffles?

The trick to attaching the Kevlar to the MM (sans baffle) is to remember to attach the Kevlar to the MM before the glue dries. Tie a slip knot on the Kevlar, loop it over the MM tube, thread the Kevlar through the fore centering ring, apply glue liberally. Run the Kevlar through the MM so when you insert the MM into the aft, you don't get glue all over the cord. Pass the cord back through after the glue has dried.

 

[bjphoenix]

Any foolproof sources of cheap spools (probably 3D printed) that will work in a BT60? I'd be willing to try one as long as it works.

I just cut 2 disks out of cardboard and glued them together with a small piece of balsa in the middle. I use a small wire tie to attach it to the middle of the shock cord.

you can read the whole thread or scroll down to post #15
https://www.rocketryforum.com/threads/shock-cord-control.167471/

 

[Ronz Rocketz]

I just cut 2 disks out of cardboard and glued them together with a small piece of balsa in the middle. I use a small wire tie to attach it to the middle of the shock cord.

you can read the whole thread or scroll down to post #15
https://www.rocketryforum.com/threads/shock-cord-control.167471/

Ah, didn't see how you attached the spool.

 

[bjphoenix]

Ah, didn't see how you attached the spool.

When I was trying to think of this I was making it too complicated. You just put the spool up against the middle point of the shock cord, tie something around it to hold it to the shock cord, and wind it up. In the first photo of my thread you can see that I had a notch in the disks for the bread tie to fit into. In later versions I drilled holes through the side disks for the tie to go through. After a launch it is possible that the spool would have to be slid along the line to the midpoint to be ready for another launch.

 

[Ronz Rocketz]

When I was trying to think of this I was making it too complicated. You just put the spool up against the middle point of the shock cord, tie something around it to hold it to the shock cord, and wind it up. In the first photo of my thread you can see that I had a notch in the disks for the bread tie to fit into. In later versions I drilled holes through the side disks for the tie to go through. After a launch it is possible that the spool would have to be slid along the line to the midpoint to be ready for another launch.

I wonder if a 10’ Kevlar cord would easier to get out of a monkeypod tree?

 

[user 35280]

Those Top Flight 3” x 3” firewall chute protectors work really well in up to 1” diameter rockets.

 

[ab.curtis]

Hi,

I have recently started looking into DD for the first time. I'm currently trying to devise a design so the drogue and main parachute are packed in the same section but they don't release at the same time. I was wondering if you had any experience in this area and if you have any advice on how to approach this?

 

[Tractionengines]

Hi,

I have recently started looking into DD for the first time. I'm currently trying to devise a design so the drogue and main parachute are packed in the same section but they don't release at the same time. I was wondering if you had any experience in this area and if you have any advice on how to approach this?

We need some details to help at all. What size rocket (diameter, length, weight, etc), what kind of recovery devices (motor eject with chute release, dual deploy altimiter, etc.)

There are ways to have both in the same space and deploy at different times. But since this is the "low power forum", I will note most of things for "bigger" rockets don't work easily (if at all).

 

[Sooner Boomer]

Hi,

I have recently started looking into DD for the first time. I'm currently trying to devise a design so the drogue and main parachute are packed in the same section but they don't release at the same time. I was wondering if you had any experience in this area and if you have any advice on how to approach this?

It's unusual that you would need this for a low power rocket, but the easiest way would be to use motor eject and a Jolly Logic Chute Release. The drogue would come out at motor eject, as would the parachute "bundle". The JLCR would release the parachute to open at the programmed altitude.

 

[Grant_Edwards]

If you want a sure-fire method, use a deployment bag. Sky divers have been doing it for decades.

Fruity chutes sizes bags to the tube. They start at 3-inch tubes. Rocketman sizes to the chute. They start at 24" chutes.

That seems a bit large for the vast majority of LPR rockets.

 

[cwbullet]

If you make something 100% foolproof, they will make a better fool.

Isn’t that the truth. I walked a group of students through proper shock cord and parachute preparation. They still screwed it up.

 

[Bat-mite]

That seems a bit large for the vast majority of LPR rockets.

My mistake. I read posts via the "New posts" button, and often don't stop to look at what forum it is in.

 

[boomtube-mk2]

Parachutes?

Real Men just "Lawn Dart" them!

 

[Banzai88]

Parachutes?
View attachment 490219
Real Men just "Lawn Dart" them!

If the camera was present, that must've been an epic video!

 

[Grant_Edwards]

Parachutes?
Real Men just "Lawn Dart" them!

Chuck Norris just catches them when them come back down.

Or, if he's in a hurry, when they're on their way up.

 

[boomtube-mk2]

Well, we can't all be Chuck Norris.

 

[beeblebrox]

Well, we can't all be Chuck Norris.

 

[beeblebrox]

I finally tried out the "Mesh Parachute" as outlined in an Apogee Newsletter. It deployed and worked great. The biggest issue is that there is double the material volume (Ignoring the holes in the mesh) Therefore it takes up more room in the body tube. The flight was in an AeroTech Mustang with an E-motor...

No shroud lines to tangle... Mesh and top of chute loosely sewed together with kevlar thread.
Attachment button is 3D printed but could be made from two 1" disks of 1/8" plywood. These are attached as a sandwich at the center of the mesh.
Note: The Mesh must be polyester, NOT Nylon... very important.

 

[PhlAsh]

View attachment 490350

I got my Washington Capitals t-shirt on one of these!

 

[Back_at_it]

The method I use is to fold the parachute in half, then in half again until I have a quarter chute. Next I tuck the lines into the chute and fold it over at least one more time. The method is shown in the video below. Not my video. Just something I found on YT.



I can tell you that my failures dropped to almost zero when doing this. The old method of wrapping the lines around the outside of the chute was very problematic for me and looking back at it, really not a very good idea.

As for the nylon vs plastic. There is nothing wrong with plastic chutes. I still use them a lot. In fact I probably use them 10 to 1 over nylon. Nylon gets used in my larger rockets but for most stuff BT60 and smaller, it's typically plastic. They are often times easier to pack and lighter.

A couple of habits I had to get out of. The first was keeping my chutes in the rockets. I don't do this anymore. So no more prepping rockets the day before. The chutes are kept in my range box and are attached to the rocket just before flight. I also open them up completely to ensure they are in good shape and not sticking. If I'm flying on a really cold day, I'll keep the range box inside the car. This keeps everything warm. Stiff plastic or even nylon isn't happy. I'm also old enough now that I don't go fly much when it's below freezing.

 

[Joekeyo]

Yes to all. Nylon chutes help, shroud lines tucked in helps. Don't cram it in too tight. Size below BT-50 doesn't work well. Good Luck.

 

[4regt4]

Parachutes?
View attachment 490219
Real Men just "Lawn Dart" them!

I keep looking at this post and laugh each time. The photo and the text need to be made into a poster.

Seriously.

Hans.

 

[brockrwood]

I keep looking at this post and laugh each time. The photo and the text need to be made into a poster.

Seriously.

Hans.

Whoa! Serious core sample! Been there. Done that.

 

[brockrwood]

Some people on the interweb say tying a loop in the shock cord about 3/4 of the way up the shock cord, and then attaching the parachute to the loop with a snap swivel will prevent tangling. I will try that.

 

[shockie]

This:


also see how the Ruskies do it for Parachute durations.

Best advise I ever got on packing Parachutes: Talcum powder,. This includes talcing the shroud lines.

Yeah I know J&J was found guilty for talc causing cancer, but only if you use it around your vagina. Every day, for like 25 years.

 

[Hobie1dog]

I've tried to rid myself of all of the small diameter rockets as they're just isn't any room for even a plastic parachute in my opinion, And I tend to like nylon chutes instead of the plastic. After reading some of the post on here I don't think I will wrap the shroud lines around the chute anymore

 

[bad_idea]

I've tried to rid myself of all of the small diameter rockets as they're just isn't any room for even a plastic parachute in my opinion

Why not use a streamer, at least for the light ones?

 

[Tractionengines]

I've tried to rid myself of all of the small diameter rockets as they're just isn't any room for even a plastic parachute in my opinion, And I tend to like nylon chutes instead of the plastic. After reading some of the post on here I don't think I will wrap the shroud lines around the chute anymore

What do you consider "Small Diameter" ?

We have some Mach1 BT-50 Fiberglass Rockets with LOC or 12" Nylon parachutes. It fits, and flys well. ( Does take a bit of careful packing to make sure it slides easily, but not too bad.)

My Son's Mach1 BT-50 Razer has a 400# Kevlar leader, 3"x3" Nomex Blanket, then 12ft of LOC 3/16 Tubular Nylon, with the 12" Nylon chute tied on about 18" from the nosecone. When we push it on a Quest D20, I even squeeze in a beeper...Which helped find it in a corn field last year.

Than there is the Mach1 BT-20 Exiter... that started with a streamer, but came down way too fast for my taste. Changed to 9" Nylon parachute. Now THAT ONE takes a bit of work to pack.

So... Nylon chutes can fit in "smaller" body tubes. (With shroud Lines INSIDE the Canopy, NOT wrapped around it.) If you want I can take photos of the Razor, and how that packs... Just let me know.