Chute Reefing

[JAL3]

I have seen refference to reefing parachutes so that they open more slowly. If I understand the procedure correctly, something is put on the shrouds near the canopy to prevent full opening immediately. The reefing device slides down the shrouds towards their gather point so that the chute opens more slowly over time, lessening the shock.

Do I have this right?

If so, how does one go about actually doing it and does it work well?

If not, what is it that I am failing to understand?

I'm thinking of trying this to keep the shock of deployment from snapping of the LES of my Sheri's Mercury Redstone. I have some additional precautions to take as well.

 

[sandman]

How about running the shroud lines through the holes in a button?

 

[JAL3]

How about running the shroud lines through the holes in a button?

???????

While I'll be the first to admit I am rather portly, none of my clothes is jumbo enough to have button holes that would handle that!

I think I'm missing something.

 

[Bill P]

I have seen refference to reefing parachutes so that they open more slowly. If I understand the procedure correctly, something is put on the shrouds near the canopy to prevent full opening immediately. The reefing device slides down the shrouds towards their gather point so that the chute opens more slowly over time, lessening the shock.

Do I have this right?

If so, how does one go about actually doing it and does it work well?

If not, what is it that I am failing to understand?

I'm thinking of trying this to keep the shock of deployment from snapping of the LES of my Sheri's Mercury Redstone. I have some additional precautions to take as well.

You have it right.

I've never seen one used. Giant Leap has a video of their "slider" working (products => recovery - middle of the page). I hope that helps.

 

[JAL3]

You have it right.

I've never seen one used. Giant Leap has a video of their "slider" working (products => recovery - middle of the page). I hope that helps.

That does help and it makes sense although I imagined the implementation differently.

They don't say what size their product is recommended for so I sent an email.

 

[als57]

OK ; I'm confuswd then. :confused2:

I always thought of reefing as shortening the shroud lines so the chute did not fully deploy. Like the slider on Rocketman chutes. It stays in place once set.


Al

 

[JAL3]

OK ; I'm confuswd then. :confused2:

I always thought of reefing as shortening the shroud lines so the chute did not fully deploy. Like the slider on Rocketman chutes. It stays in place once set.


Al

I've heard the term used that way as well but that's not the way I intended in my question. It may be that I'm confused and using the term incorrectly.

 

[Reinhard]

In professional applications, you'll often find reefing lines that restrict the opening of the chute. These are then cut by a pyrotechnic line cutter, to allow the chute to fully inflate. IIRC the chutes on the SRBs are opened in 4 stages.

Reinhard

 

[sandman]

I meant something like this.

Kind of exadurated. I drew it in a hurry.

View attachment Reef lines.pdf

 

[JAL3]

I meant something like this.

Kind of exadurated. I drew it in a hurry.

That makes sense.

Are there any guidlines for the proportions of the "button" to the diameter of the chute?

Is it secured in place in any way before deployement?

Is it rigid like plywood or some sort of fabric thing?

As long as you got answers, I'll probably have questions.

 

[JAL3]

In professional applications, you'll often find reefing lines that restrict the opening of the chute. These are then cut by a pyrotechnic line cutter, to allow the chute to fully inflate. IIRC the chutes on the SRBs are opened in 4 stages.

Reinhard

Thanks for the info. I didn't know that.

I shudder to think of the potential for doom for anything depending on my and a pyrotechnic line cutter.:jaw:

 

[kandsrockets]

You can use a ring. I have used a small key chain ring and it worked great. It slows down the chute from opening all at once.

 

[gpoehlein]

Of course, there is always the "cheap and dirty" route - just wrap a small piece of masking tape around the shroud lines where you want it reefed. Easy to use, easy to remove (don't leave it on for very long as the adhesive might transfer to the shrouds).

 

[JAL3]

You can use a ring. I have used a small key chain ring and it worked great. It slows down the chute from opening all at once.

How tight does the ring need to be?

 

[JAL3]

Of course, there is always the "cheap and dirty" route - just wrap a small piece of masking tape around the shroud lines where you want it reefed. Easy to use, easy to remove (don't leave it on for very long as the adhesive might transfer to the shrouds).

Wouldn't that not slide down to fully open the chute?

 

[sandman]

That makes sense.

Are there any guidlines for the proportions of the "button" to the diameter of the chute?

Is it secured in place in any way before deployement?

Is it rigid like plywood or some sort of fabric thing?

As long as you got answers, I'll probably have questions.

My wife sews so I just ask her for a button and she hands me a big can of buttons.

Slide the button up and the chute (hopefully) deploys a bit slower as the button slides down.

Dirt simple really.

 

[luke strawwalker]

Last year Challenger 498 did some night launches out here at the farm. I "cloned" a BB on the cheap (paper coated paper towel tube, papered balsa fins, homemade motor mount, balsa standoff) and used one of those children's toys, the kind with the 3-4 inch clear plastic sphere with the rotating LED gizmo in the globe, with a battery handle and button underneath. Looked great, but it was HEAVY (D and E powered BB)

Anyway, I knew I needed a big chute, and I had a couple of those freebie Apogee 32-34 inch chutes that Tim sends out when you order stuff from Apogee, so I used that. I knew though with the "warp drive" (toy) being as heavy as it was it would create one heck of an opening force when the chute popped, because the thing was going to be moving at a pretty good clip, and I didn't want any seperations, especially at a night launch. SO, I put a plastic bead over the shroud lines before I installed the locking snap swivel. This was just a small decorative bead that my wife had laying around-- the kind you get at hobby lobby. The hole is about 1/16 inch in diameter, and the bead is about 1/4 inch diameter (plastic). I gathered the shroud line loops like I was going to install them into the swivel, pinched them tightly, and threaded the loops through the hole in the bead. The small hole and fairly large diameter means the bead makes a bit more friction, giving the chute a little more time to slow down before it opens fully(some of those ultra-cheap 'friendship beads' have much larger holes and smaller diameters, therefore less friction so they don't reef as much because they slide down the shrouds too fast). It worked great and was quick and easy to do.

Depending on your packing technique it's virtually no change to use it. I grab the peak of the chute (or pinch the top around the spill hole, pull the chute to a point, pull the shrouds taut, fold all the 'billows' to one side to form a wedge, fold the tip to the shrouds, fold the 'billows' over the top, and roll the thing up. Once the canopy is rolled, slide the bead from the swivel up the shrouds to the canopy, and roll the shrouds around the rolled canopy. Ready to install in the rocket. When she deploys, the shrouds unroll and the bead is at the top, the chute unrolls and starts to catch air, and the billows start to snap open, but the bead is holding all the shrouds together right at the canopy, so the billows, now filled with air, starts to fill the chute with air, but it's only about 8 inches in diameter at this point, so there's no abrupt 'tug' or snap on the rocket or chute, lessening the 'braking force' of the chute. As the chute fills, the lines are pulled away from each other by the chute, sliding the bead down the shrouds, allowing the chute to open fully. The whole process probably doesn't take much over a second, but it slows the rocket down far more gradually than a loud chute POP! would! Worked great!

Later! OL JR

 

[hognutz63]

In professional applications, you'll often find reefing lines that restrict the opening of the chute. These are then cut by a pyrotechnic line cutter, to allow the chute to fully inflate. IIRC the chutes on the SRBs are opened in 4 stages.

Reinhard

Here is an example of what you are talking about.

https://www.youtube.com/watch?v=jJ0oKhV8f1A

 

[Porthos II]

Reefing and a slider are two completely different methods.

Slider:

A slider is an accessory that is located in the suspension lines. In skydiving it is generally a 12”x18” (give or take a few inches in either direction) piece of nylon that has a large metal grommet in each corner for the suspension lines to pass thru. When packing the parachute, the slider is pulled all the way up to the top of the suspension lines to retard the opening of the parachute. As the parachute opens, it forces the slider down until the parachute is fully inflated. In BASE jumping we use a mesh slider so that the air flow has less effect on the slider moving down the lines. When we want the fastest opening, we remove the slider, or pack slider down. A delay over 3 seconds with slider down will spank you harder than you would ever wish.

Reefing:

Reefing is done with a separate line that encompasses the bottom of the chute. Is comes with a pyro line cutter that at a predetermined time (usually 1 or 2 seconds after initial opening) cuts the line and lets the parachute open completely.

Erik

 

[JAL3]

My wife sews so I just ask her for a button and she hands me a big can of buttons.

Slide the button up and the chute (hopefully) deploys a bit slower as the button slides down.

Dirt simple really.

That makes sense. My reaction was based on the size of the shrouds. I have not seen a button with enough and big enough holes to fit the shrouds on this chute except maybe once on a clown suit at the circus.

 

[Chrisn]

He might not of known the scale of this rocket, and thought the shroud lines were cotton.

 

[JAL3]

He might not of known the scale of this rocket, and thought the shroud lines were cotton.

You're absolutely right.

I hope I did not give the impression that I was seriously offended. I wasn't offended at all. We need a dedicated "sarcastic remark" smiley.

I appreciate the input and information. I don't want to launch this without the LES but I also want to minimize the chances of it shearing off when the chute deploys.

 

[JOAT]

We need a dedicated "sarcastic remark" smiley.

It's right here-

 

[gpoehlein]

Wouldn't that not slide down to fully open the chute?

Never happened to me - the adhesive on the tape holds it it place. Of course, it also depends on the size of the chute you're using it on. I've reefed chutes with tape on smaller rockets with smaller plastic chutes - I haven't tried it with nylon chutes (don't have any yet - gotta start though - I shredded 5 of the six shroud lines on the plastic chute that came with my Big Daddy when I flew it for the first time on an E11 )

 

[JoeG]

I thought I remembered someone offering this some time ago. I have seen it used successfully. I believe it was similar to the "button" type.

However, you may want to read this.

https://www.publicmissiles.co/imag/PMLRecoveryComponentsFAQ.pdf

• We no longer recommend use of the Gradual Deployment feature on our larger
chutes. Successful operation of the system is too dependent on specific flight
conditions and exact setup of the system. We have not sold/shipped parachutes
equipped with Gradual Deployment for a number of years, but some customers may
still have some Gradual Deployment chutes.

 

[TWRackers]

I thought I remembered someone offering this some time ago. I have seen it used successfully. I believe it was similar to the "button" type.

However, you may want to read this.

https://www.publicmissiles.co/imag/PMLRecoveryComponentsFAQ.pdf

The link doesn't work, even if you change the ".co" to ".com". :confused2:

 

[rocketguy101]

Go to the Irvin Aerospace site, scroll down to the "Recovery Systems Design Guide AFFDL-TR-78-151" and download that (its a big file!!!). You will learn more than you ever wanted to know about parachutes!!

 

[Chrisn]

The link doesn't work, even if you change the ".co" to ".com". :confused2:

This one https://blastzone.com/pml/images/PMLRecoveryComponentsFAQ.pdf

or this one https://publicmissiles.com/images/PMLRecoveryComponentsFAQ.pdf

Both the same file and both work here. Wonder where JoeG got his URL from

 

[troj]

Use a small pilot chute and a deployment bag -- it will do all of what you're after, and there's no sizing or calculation to be done.

In addition to keeping things neat a tidy, a properly used deployment bag also makes sure the lines are stretched out before the canopy begins to inflate, and will slow the opening of the canopy, resulting in a much softer opening.

When a parachute is just tossed out and allow to inflate, they have a tendency to inflate and stop, while the rocket still falls, until it hits the end of the recovery system, putting a tremendous load on everything.

-Kevin