I have An Idea...and Some Questions Using the JLCR...

[Hooked On Rockets]

I just got my 4" Goblin a lot closer to fly ready, I just picked up the JLCR a couple of weeks ago.
I've been kinda looking for some ideas to use it for "dual deploy"-so to speak...

It would be easier to draw a picture than to try to explain..so I drew a picture...
(Pardon the crudeness, but the elements are there! LOL)

Here's the picture....


Here's the idea....

The idea is to have a section of the main harness line held captive in the Chute Release and a separate drogue line attached to the main chute attachment loop.
It then passes through a metal "slip loop" tied with a simple knot in the main line.
Upon deployment, the drogue chute is pulled out and the main is held lower wit the Chute Release.
When it reaches release altitude, the main hopefully clears the drogue and when it opens, it pull the drogue down to the "slip loop" below the main chute.
The drogue remains open ( I know it "steals" air from the main so to speak) and hopefully adds some drag and PERHAPS reduces the chance of a tangle...provided that the main clears the drogue without a tangle...
I'm also thinking that it could reduce main deployment shock by the drag that it takes to pull the drogue down through the "slip loop".

Here's the questions...

Has anyone ever tried this?
Did it work?
Is this a good idea?

Thanks!!!!

 

[anbhtblr]

I just got my 4" Goblin a lot closer to fly ready, I just picked up the JLCR a couple of weeks ago.
I've been kinda looking for some ideas to use it for "dual deploy"-so to speak...

It would be easier to draw a picture than to try to explain..so I drew a picture...
(Pardon the crudeness, but the elements are there! LOL)

Here's the picture....
View attachment 378277

Here's the idea....

The idea is to have a section of the main harness line held captive in the Chute Release and a separate drogue line attached to the main chute attachment loop.
It then passes through a metal "slip loop" tied with a simple knot in the main line.
Upon deployment, the drogue chute is pulled out and the main is held lower wit the Chute Release.
When it reaches release altitude, the main hopefully clears the drogue and when it opens, it pull the drogue down to the "slip loop" below the main chute.
The drogue remains open ( I know it "steals" air from the main so to speak) and hopefully adds some drag and PERHAPS reduces the chance of a tangle...provided that the main clears the drogue without a tangle...
I'm also thinking that it could reduce main deployment shock by the drag that it takes to pull the drogue down through the "slip loop".

Here's the questions...

Has anyone ever tried this?
Did it work?
Is this a good idea?

Thanks!!!!

Could the drogue slide up to the main and tangle?

 

[Zeus-cat]

You have to be careful that you do not put too much tension on the chute release. I have seen early deployments due to too much stress on the chute release rubber band.

 

[Bat-mite]

I don't think having a drogue really adds anything. The bundled main held by the JLCR acts like a drogue in that it creates drag and helps keep the NC away from the BT. One always has to weight the ROI when adding complexity.

 

[tim cubbedge]

One concern I have is the drogue getting tangled with the main. I’ve done it myself and have seen others as well. It can be done as there was a thread once upon a time with similar question but I think the key is keeping the drogue properly distanced from the main.

 

[dhkaiser]

I beleive JL cautions against undue stress to the JLCR tether and its attachment point. Something to consider.

 

[Handeman]

What makes you think the drogue will slide down? Once the main opens and all the weight is on the main, there is nothing to make the drogue drop, it will move as high up the chain as it can.

I would also expect the drogue to pull as much cord out of the JLCR bundle as there is available.

 

[Hooked On Rockets]

Could the drogue slide up to the main and tangle?

That's what the "slip ring" is for, to pull the drogue down below the main...

You have to be careful that you do not put too much tension on the chute release. I have seen early deployments due to too much stress on the chute release rubber band.

That is the weak link-the rubber band, I've sure considered that......

I don't think having a drogue really adds anything. The bundled main held by the JLCR acts like a drogue in that it creates drag and helps keep the NC away from the BT. One always has to weight the ROI when adding complexity.

The drogue is to help slow it down more than the packed main would act as a drogue...
the 36" main that came with it from Loc packs pretty small...not much drag there and I'd like to avoid chute shock as muck as possible...
Also, I did FORGET to add the nose cone in the drawing..arrggg

One concern I have is the drogue getting tangled with the main. I’ve done it myself and have seen others as well. It can be done as there was a thread once upon a time with similar question but I think the key is keeping the drogue properly distanced from the main.

I'm maybe thinking backward terms here, but my worry is that the main gets tangled in the drogue when the release opens.

I believe JL cautions against undue stress to the JLCR tether and its attachment point. Something to consider.

I saw that in the literature,...it does all come down to the "rubber band"....

What makes you think the drogue will slide down? Once the main opens and all the weight is on the main, there is nothing to make the drogue drop, it will move as high up the chain as it can.

I would also expect the drogue to pull as much cord out of the JLCR bundle as there is available.

Look at the drawing, once the main opens, the weigh pulls the drogue cord through the "slip loop" mounted below where the main is attached. The main having greater drag will pull the drogue down a pre determined length governed by the length of the drogue cord.
As to the drogue pulling out all the slack...I've considered that as well.....

I'm just trying to think of something "new" to try....and to take advantage of the JLCR...

It was an idea....I guess not a good one!!! LOL

Thanks for the replies!!!
I appreciate the advice!!!!
Y'all been here longer than I !!!

 

[afadeev]

The idea is to have a section of the main harness line held captive in the Chute Release and a separate drogue line attached to the main chute attachment loop.

That's a LOT of extra weight sitting on the JL CR's rubber line, which makes it that much more likely that things will get pulled out and the chute will deploy prematurely.
The is explicitly advised against by the JL CR product guide "NEVER be exposed to shock loads. You should be able to pull your nosecone and fuselage all of the way apart until your shock cord is stretched tight without affect Chute Release's grip on the chute."
https://www.jollylogic.com/wp-content/uploads/2015/12/JollyLogicChuteReleaseWeb.pdf

I don't think having a drogue really adds anything. The bundled main held by the JLCR acts like a drogue in that it creates drag and helps keep the NC away from the BT. One always has to weight the ROI when adding complexity.

+1.
JL CR tied main is a mini-streamer.
Unless your rocket is soooooooo heavy that you are concerned that the shock of an inflating chute tearing-off the shroud lines, I don't see any upside from this complexity.

The drogue is to help slow it down more than the packed main would act as a drogue...
the 36" main that came with it from Loc packs pretty small...not much drag there and I'd like to avoid chute shock as muck as possible...

Why?

What descent speed under drogue/streamer are you targeting?

a

 

[dhkaiser]

I was not refering to the rubber band rather the tehter attaching it to the shock cord and the attachment point on the JLCR. JL warns about too much stress on them.

"I believe JL cautions against undue stress to the JLCR tether and its attachment point. Something to consider.
I saw that in the literature,...it does all come down to the "rubber band"...."

 

[Bat-mite]

The drogue is to help slow it down more than the packed main would act as a drogue...
the 36" main that came with it from Loc packs pretty small...not much drag there and I'd like to avoid chute shock as muck as possible...

Rocketry is largely experimental. If you are that concerned, try it. For much of what we do, there is no "right" answer. You've heard from several people that they wouldn't do it. Ultimately, it's up to you.

 

[anbhtblr]

Could the drogue slide up to the main and tangle?

Sorry, I didn't originally recognize the slip ring was attached to the harness.

 

[John Beans]

Responses here are all pretty helpful.

The first principle here is: Chute Release keeps a parachute bundled up in the slipstream. That is the only load it should experience.

You should be able to pull the rocket and drogue apart as hard as you can and never affect Chute Release.

At the risk of mis-interpreting your sketch, I would expect the drogue in your sketch to immediately pull the folded line out through the ring at ejection (at inflation, there's a peak load that will yank mightily). If the bundle then became loose once the line was pulled out, or if the line being pulled out actually pulled some chute with it, you'd likely get an apogee inflation and a long walk.

Maybe try re-designing it with three rings (a larger ring right below each chute, and a smaller ring fixed on the shock cord. Probably doesn't make sense until you sketch it, but the drogue chute when inflated will pull the chute bundle's ring tight against the small ring, then when the main inflates it will pull the drogue line until its big ring catches in the small ring. Kind of like a teeter-totter: whichever chute pulls the hardest stays on top.

The disadvantage of this is that knots and rings weaken the ultimate strength of the setup. But assuming you have sturdy lines and rings, that's manageable.

You don't show how Chute Release would be tethered, but I'd suggest you loosely slip-hitch it to the shock line below it. Never tether in such a way that the tether can ever—no matter how much tension is on any portion of the shock cord—be pulled. It is just there to catch the weight of Chute Release so you won't loose it. The plastic tether point and 300 pound test line we provide are both massively over-engineered for that task.

If you happen to tether Chute Release to say, the nosecone, it would be yanked off the bundle and best case you'd get an apogee inflation. Worst case is that you RUD your Chute Release. Ouch.

 

[Hooked On Rockets]

Wow,
Thanks for all the replies!!!!!

I guess my main concern is not so much pulling things apart, I'm trying to avoid the big ZIPPER.

My thought is, that if the rocket is coming down with the "tail-up" with the chute un-released from the JLCR,
Wouldn't that be the equivalent as a "late-deploy" and a recipe for a zipper???

I've been looking at a couple of videos of the JLCR in use and it kinda looks about 50/50 whether the rocket falls "tail-down"
or "tail-up" BEFORE the chute release opens.

And for my mis-speak earlier about the drogue slowing the rocket down before the main opens,
I guess I meant that the drogue (SMALL drogue) is to make sure that the rocket is "tail-down" when the release unfurls the main.

I'm just worried about a zipper, if it falls "tail-down" when the chute opens, I'm pretty confident in the rocket to stay together.

Maybe try re-designing it with three rings (a larger ring right below each chute, and a smaller ring fixed on the shock cord. Probably doesn't make sense until you sketch it, but the drogue chute when inflated will pull the chute bundle's ring tight against the small ring, then when the main inflates it will pull the drogue line until its big ring catches in the small ring. Kind of like a teeter-totter: whichever chute pulls the hardest stays on top

You should be able to pull the rocket and drogue apart as hard as you can and never affect Chute Release.

I actually had intended to add the extra ring on the drogue chute cord for that very reason...so all the force stays on the main chute cord instead of the JLCR.
In my haste to get the crude drawing done and uploaded, I didn't add all the components, like the NOSE CONE!!....Dohhh (I slap myself in the head!!!) LOL.

As far as tethering the JLCR...absolutely, I just didn't include that in the drawing because I kinda felt like that's a given to tether that properly
as per instructions. I researched the JLCR for over a month before I made the plunge!
AWESOME investment!!! I have complete confidence in it, as long as I have MY ducks in a row!!!!

And you got the "teeter-totter" idea perfectly!!
That's exactly my whole idea...when the big chute opens, the larger drag pulls the smaller chute down so it don't tangle the big one, provided that
the main don't get caught in the drogue when the chute release opens.

THANKS EVERYONE!!!
ALL your responses have been VERY helpful!!!!
I'm just trying to figure it all out and make my mistakes on paper instead of on the launch pad!!!

 

[Bat-mite]

I'm just trying to figure it all out and make my mistakes on paper instead of on the launch pad!!!

As should we all! Kudos.

 

[afadeev]

I guess my main concern is not so much pulling things apart, I'm trying to avoid the big ZIPPER.

My thought is, that if the rocket is coming down with the "tail-up" with the chute un-released from the JLCR,
Wouldn't that be the equivalent as a "late-deploy" and a recipe for a zipper???

Rocket will not be coming down "tail-up" if the ejection charge fired at apogee.
The drag from the separated nose-cone + harness, coupled with the heavy fin can, all but guarantees that the separated rocket airframe will be coming down with the aft end below the open body tube. It may not be pointing straight down, but the fin-can will be leading the way.

The only way you will achieve "tail-up" scenario is if the ejection charge failed to fire properly, or in a timely fashion, and the rockets is coming in ballistic. In that case, JL CR release is the least of your worries.


HTH,
a

 

[Hooked On Rockets]

Rocket will not be coming down "tail-up" if the ejection charge fired at apogee.
The drag from the separated nose-cone + harness, coupled with the heavy fin can, all but guarantees that the separated rocket airframe will be coming down with the aft end below the open body tube. It may not be pointing straight down, but the fin-can will be leading the way.

The only way you will achieve "tail-up" scenario is if the ejection charge failed to fire properly, or in a timely fashion, and the rockets is coming in ballistic. In that case, JL CR release is the least of your worries.


HTH,
a

I sure hope you are right......
Again, I been looking at YT videos and when there is a "laundry failure", it looks like a 50/50% chance of a "tail-up/tail-down"....
whether or not it has a delayed chute release...

it's just the silly ole' physics....
BY GOD THERE OTTA BE A LAW!!!!!
LOL

I lust feel more comfy with a drogue/pilot chute to make sure my tail is DOWN when the chute deploys....
I SERIOUSLY have no doubts about my rockets' structural integrity.....
I over build....and over prime and over paint.....

SS

 

[Joe Rocket 97]

I've read about guide chutes along with a main chute with a chute release being used in a single break dual deploy. Has any one used this method of recovery?

 

[dhkaiser]

Yes last MWP, 4" Sky Scraper....

 

[Zman1961]

I use a guide chute as well. I did make a mistake once with the JLCR. I failed to secure my Nomex blanket to the shock cord, and the drag from the vertical descent caused it to slide up and around my main chute bundle. The main never opened. Fortunately, due to overbuild and nice grass, there was no damage. Close examination showed that the JLCR had worked properly, but the chute didn't open because the air stream could not get to it. If you use a nomex blanket like that, secure it to the shock cord a couple feet below the parachute bundle. I have never had a zipper while using the guide chute.

 

[Nathan]

I have had four JLCR's. After several crashes with JLCR's, I don't use them anymore. They are not as reliable as conventional dual deploy.

 

[crossfire]

I have had four JLCR's. After several crashes with JLCR's, I don't use them anymore. They are not as reliable as conventional dual deploy.

Nathan
Out of 25+ flight with my JLCR I have had maybe 3 problems 2 were my mistake and 1 I really don't happened. All were in HP rockets.

 

[Handeman]

I have had four JLCR's. After several crashes with JLCR's, I don't use them anymore. They are not as reliable as conventional dual deploy.

You'll get no argument from me, but I still use them on non-electronics rockets.

 

[Nathan]

You'll get no argument from me, but I still use them on non-electronics rockets.

I built my Upscale Onyx specifically to use with a JLCR. It has landed hard twice. I am now repairing it for the second time and as soon as Madcow ships me the parts I ordered I will be converting it to head-end dual deploy.