Jolly Logic Chute Release

[rcktnut]

A few more things here, after cutting the bungee to size I melt the cut ends. Bungee frays a little and melting the ends will keep it nice and neat. I also like to get my bigger chutes packed at home so after packing I use a strip of Velcro to wrap around the packed chutes. It keeps them ready to go and you can also adjust the CR with the Velcro on.

 

[o1d_dude]

A few more things here, after cutting the bungee to size I melt the cut ends. Bungee frays a little and melting the ends will keep it nice and neat. I also like to get my bigger chutes packed at home so after packing I use a strip of Velcro to wrap around the packed chutes. It keeps them ready to go and you can also adjust the CR with the Velcro on.

Great idea!

 

[ZEDL1]

Yes, it was the braided elastic that I was referring to in my question. Thank you both for your help. Very much appreciated.
Jim

 

[Winston]

Maybe this has been discussed elsewhere, but when HPR nylon 'chutes are laid out with gores stacked on top of each other and then grabbed between thumb and index finger just above the base of the 'chute, the base is considerably larger in diameter than the grabbed section because of the folded hemline and the shroud line attachment points. This would, I'd think, keep the JLSR from slipping off during descent and would allow the upper section of the 'chute (most of the 'chute) to unfurl and act a bit like a drogue 'chute during the descent.

Is there a reason why this method of 'chute reefing isn't used?

 

[Orien]

I too have experienced the Chute Release “failure” of not turning it on before walking away from the pad.

Talk about feeling stupid when you find the chute bundle neatly tied up next to the remains of your rocket...and your JLCR is NOT turned on...”Go Fever” strikes again.

"Go Fever" for me was fatigue, dehydration, and sunburn. My Iris fell from 3700' with nothing but a streamer deployed due to the band digging into the chute too much. I also didn't powder it with corn starch between flights and felt that tackiness coming back. But I was by myself with no help and no shelter and it's like "I gotta get this thing in the air before I die from exposure out here..."

The Iris is fine, by the way. Zero damage. I think the tailcone retainer saved it's life at impact.

 

[tim cubbedge]

Is there a reason why this method of 'chute reefing isn't used?

I have seen it done many times and have done it myself.

 

[DaHabes]

Most AT motors' delay charges can be drilled out to shorten the delay timing.

Not exactly. There are 20 Single Use motors that are not delay-drillable, 3 LMS motors that you can pick a set delay and 35 DMS motors that are delay-drillable. 23 out of 58 are not drillable - 40%.

 

[DaHabes]

I orient the pin at a tangent to the bundle.

If the pin isn't at nearly a tangent, the band isn't tight enough. Always pack, ground test and repack the same way if the CR opened. If not. repeat with a tighter pack or shorter band.

 

[dhbarr]

EDIT: Ignore my untimely response to an old post.

 

[TomBroad]

Amidst this long discussion about rigging the Jolly Logic, the one item I have not seen mentioned is the knot used to secure the tether. With deference to @John Beans — I have been climbing and caving for many years, and the simple overhand knot on the tether (as shipped) is NOT secure in such a stiff and slippery cord (see first photo). You paid big $$$ for your JL so don’t lose it because the tether came untied.
My recommendation is to re-tie the tether using a “Grapevine” (aka: “Double Fisherman’s”) knot (second photo). This is a self-locking knot - the harder you pull it, the more secure it gets. It also avoids sharp bights which are a problem with Kevlar. It’s a PITA to tie in this cord, but worth the piece of mind. To learn how to tie this, just Google “grapevine knot.”

 

[Handeman]

Amidst this long discussion about rigging the Jolly Logic, the one item I have not seen mentioned is the knot used to secure the tether. With deference to @John Beans — I have been climbing and caving for many years, and the simple overhand knot on the tether (as shipped) is NOT secure in such a stiff and slippery cord (see first photo). You paid big $$$ for your JL so don’t lose it because the tether came untied.
My recommendation is to re-tie the tether using a “Grapevine” (aka: “Double Fisherman’s”) knot (second photo). This is a self-locking knot - the harder you pull it, the more secure it gets. It also avoids sharp bights which are a problem with Kevlar. It’s a PITA to tie in this cord, but worth the piece of mind. To learn how to tie this, just Google “grapevine knot.”

I lost my first JL on the 4th flight. Since then, I've replaced the included tether with a 1/8" Kevlar tether tied with a much better knot. Haven't lost one since. You're grapevine knot would have probably solved the problem, but I just feel better with the larger and stronger Kevlar.

 

[Highpowerrocketyahoo]

I don't know a damn thing about rigging. I just know that every time i exited an airplane or popped a ring while in the Army, my laundry came out. Lol

Always buy the riggers a beer!

 

[hball55]

Um...literally every single thing he did to that chute either increases the risk of line entanglement or prevents proper chute inflation.

Rolling with the lines in it a parachute is basically the worst thing you can do to it in terms of deployment. It would actually be better if it just bunched it into a ball.

But hey, I'm just some guy on the internet, right? I'm certainly not a guy who is a qualified Army parachutist studying to be an FAA rigger, who learned how to pack high speed drogues, large cargo chutes, and man-rated chutes from master riggers.

If you can spare any time from making pithy, uninformed comments, spend about 5 minutes learning about, anecdotally, what I believe to be the cause of most rocket failures - recovery failure. Google parachute packing and see how many chutes are rolled like a burrito and let me know...I'll wait.

I flew JLCR the other day in a Madcow Screech on an i327DM to 4,978'; RRC2 altimeter triggered separation at apogee and the rocket tumbled to 500' (pretty sure it was 5, but it might have been 700). Either way, no issues, great chute inflation and recovery.

The biggest airframe I've used JLCR is my 5.5" Madcow Nike booster with an M2020 that hit 10,155' and my altimeters popped the apogee charge. I had a 30" drogue pull everything out and the JLCR released the main (84" or 96", can't recall exactly) with no issues. That pig weighs 6.65 kg with no motor so it is beefy.

Weight isn't the issue per se, but higher weight means bigger chutes and big chutes are tough to reef and secure with JLCR. For me, 48-54" is the biggest I am 100% confident JLCR can secure without drogues and some specific shock cord set up.

You did find the larger rubber bands under the box, didn’t you? I’ve secured a Rocketman R12 using them, with no problems.

 

[Zeta]

I'm going to buy a chute release. I Have some questions
1) I have some Aerotech motors all with long delays so my rockets are heading straight for the ground when the ejection charge deploys at high speed. will the high speed deployment damage the chute release? Or can I use these motors with the Chute release?
2) How do I figure out how fast the rocket is going just before the ejection charge fires? Can I find out by running a open rocket simulation?
3)If you knew nothing about testing a Jolly Logic Chute release how would you proceed?

Thank you,
Brian

Brian,

If you run a simulation with Open Rocket or other software, you can find the apogee for a given rocket/motor combination. Then use the delay drilling tool from Aerotech to adjust the delay time so that the event happens at apogee and your worries about high speed deployment.

~Zeta

 

[hball55]

Could be worse. Could be a glue argument.



For what it's worth, I was shown the method in that video at a large club launch about 10 years ago by one of the hobby's Old Royalty—one of those guys who took part in record altitude flights and had a job in aerospace. He took a similarly brusque attitude with me and grabbed my chute and showed me "how to do it properly." The main point he made at the time was to use the shroud lines to help do the work of opening the chute for a small rocket in which the chute really needed to be kept compact.

I don't claim to be an expert on chute folding. I do get lots of requests for videos and techniques, which when I have them I'm happy to share. A number of you have videos on the Jolly Logic site in the flights section, but I'm happy to also post your How To videos as well. Always welcome!

Things can vary greatly depending on your rocket and your chute, but there are a few things that I do believe are always important, most of which you'll see in the User Guide of Chute Release:

• I've seen "puffy bundles" fail to deploy because they trap the band—avoid that
• Since shroud lines are no longer needed to hold a bundle tight, put them inside to protect them
• Flame blankets should be tethered in such a way that they get whisked away when the shock line goes taut
• Never tether Chute Release in such a way that it gets yanked when the shock cord goes tight—the tether is just there to support the weight of Chute Release after release so that you don't lose it (the 300# kevlar line it ships with is massive overkill)
• If you are folding your chute the way you did before you started using Chute Release (or a cable cutter), you can do better
• Make sure your shrouds cannot just slide out of your bundle before release (from the flap or the from the center)
• The goal is to create a bundle you can't shake loose by hand ("shake test") but which just falls apart after release ("release test")
• Make sure your bundle will eject easily ("puff test" from the engine mount)

Anyway, send me a video. Happy to post it.

I have always wrapped my parachutes like your video shows and have had no problems.