JL Chute release question

[tOD]

I'm going to make my first flights with a
chute release this weekend. Does the compartment containing the device need to be vented?

 

[ep29030]

Well, it is always a good idea to vent the parachute area with a small hole, to relieve pressure build-up in upper airframe. For model rockets, a single 1/16 to 1/8" hole works. But once your engine kicks it out at apogee with ejection charge, then CR is in open air.

 

[Eric]

I have flown the chute release in both types. Most of the Estes kits never had a vent when built, so they never got one.

Chute Release still opened perfectly either way. But it never hurts to just add a small hole.

 

[kuririn]

Not necessary. Vent holes are only needed for devices that sense atmospheric pressure while in the rocket. The altimeter portion of the JLCR senses atmospheric pressure and releases the pin, rubber band, and chute at your programmed elevation while free falling after ejection.

Best invention ever. I'm still waiting for the JLCR II that can fit inside a BT-20 tube.

 

[tOD]

So I guess it established it's ground level reference on power- up and then calculates the release altitude from there?

 

[Jozef]

So I guess it established it's ground level reference on power- up and then calculates the release altitude from there?

Exactly..

 

[tOD]

I'm eager to try this. I have two rockets I want to use it in tomorrow, wind at the launch site is forecast for 10-15 mph, and I don't think the corn's been cut. The corn is planted in strips with fallow areas in between so it's 50/50 a rocket will land in the clear. I think I'll release at 200' and see how it goes

 

[afadeev]

I'm eager to try this. I have two rockets I want to use it in tomorrow, wind at the launch site is forecast for 10-15 mph, and I don't think the corn's been cut. The corn is planted in strips with fallow areas in between so it's 50/50 a rocket will land in the clear. I think I'll release at 200' and see how it goes

BTDT, spent 2 days looking for a rocket in the corn field.
Found it on day #2 by flying a drone over the adjacent fields and (luckily) spotted the orange chute peaking out between corn stalks.
It's deceptively difficult to estimate depth over corn fields, and most of my fruitless foot grid searching was too close to the launch pad. 200 foot JLCR deploy worked perfectly, and against me, since the rocket weather cocked into the wind, and super short open chute time did not bring it back.
YMMV.

Have fun with JLCR - it's a great tool that make dual-deploy flying easy, quick, and fun!

a

P.S.: I hate corn fields!

 

[smugglervt]

Best to include a loud buzzer/beacon to it. Corn is a pain in the butt to try and find a rocket when the corn is over 7' tall.

 

[Zeus-cat]

BTDT, spent 2 days looking for a rocket in the corn field.
Found it on day #2 by flying a drone over the adjacent fields and (luckily) spotted the orange chute peaking out between corn stalks.
It's deceptively difficult to estimate depth over corn fields, and most of my fruitless foot grid searching was too close to the launch pad...

People almost always underestimate how far a rocket has drifted. I've done it numerous times. I've recovered rockets that other people gave up on because they didn't go out far enough. My rule is just keep looking until you are ridiculously far away from the launch pad and only then turn around.

P.S.: I hate corn fields!

​

I love corn fields... when they don't have corn in them.

 

[tOD]

Best to include a loud buzzer/beacon to it. Corn is a pain in the butt to try and find a rocket when the corn is over 7' tall.

Any suggestions for a buzzer I might be able to get ahold of today?

 

[smugglervt]

I don't know what you have locally for shopping but you could probably find something like these personal alarms at a Walmart or local hardware store:

https://www.amazon.com/dp/B07BVCZKRP/?tag=skimlinks_replacement-20

 

[crossfire]

Not necessary. Vent holes are only needed for devices that sense atmospheric pressure while in the rocket. The altimeter portion of the JLCR senses atmospheric pressure and releases the pin, rubber band, and chute at your programmed elevation while free falling after ejection.

Best invention ever. I'm still waiting for the JLCR II that can fit inside a BT-20 tube.

Do you think a JCR for BT20 size rocket would be a big seller for John? A $129.00 item in a $20 rocket.

 

[kuririn]

Do you think a JCR for BT20 size rocket would be a big seller for John? A $129.00 item in a $20 rocket.

Well, right now the limiting size for the JLCR is a BT-60, I believe. The mini that John was talking about a few months ago would fit in, but not be limited to, a BT-20. Price point remains to be seen. So yeah, I think that a lot of people would like the added versatility. And there are a lot of 29 and 38mm dia. rockets that cost way more than $20.

 

[Nytrunner]

BT-20, unlikely. BT55, I'd buy it. My magician is still susceptible to loss on E's. And if it works on BT55, would it not work on 4" airframes also?

 

[tOD]

I don't know what you have locally for shopping but you could probably find something like these personal alarms at a Walmart or local hardware store:

https://www.amazon.com/dp/B07BVCZKRP/?tag=skimlinks_replacement-20

I found something similar, thanks for the suggestion.

 

[tOD]

Well, the chute release went 2/2. Some anxious moments, 200ft. is closer to the ground than I thought.

 

[Normzilla]

Well, the chute release went 2/2. Some anxious moments, 200ft. is closer to the ground than I thought.

It always does.

 

[Nytrunner]

Well, the chute release went 2/2. Some anxious moments, 200ft. is closer to the ground than I thought.

I don't think I've set it less than 300' (even BT-60 estes models)

 

[Eric]

I don't think I've set it less than 300' (even BT-60 estes models)

I love setting my JLCR at 200' with my Estes Mammoth... Works every time, and gets people nice and worried...

 

[afadeev]

I love setting my JLCR at 200' with my Estes Mammoth... Works every time, and gets people nice and worried...

Yep, 200' release works, with room to spare.
Takes ~1 second for the chute to unfurl and inflate, and at ~70 ft/sec tumble descent speeds, that still leaves 100+ feet of drifting under chute.
It does get observers' hearts beating faster, though.

Well, the chute release went 2/2. Some anxious moments, 200ft. is closer to the ground than I thought.

I bet you will go 100/100 from here on out.
JLCR works like a champ. Every time.

a

 

[Handeman]

I've set mine at 100 ft. on my Callisto sometimes. Wouldn't do that on the other rockets, but the way the Callisto falls, it works, with about 15 - 20 ft to spare.

 

[Sabrina]

I'm going to make my first flights with a
chute release this weekend. Does the compartment containing the device need to be vented?

I didn't see anyone else state the obvious... so here goes -

When in doubt, RTFM. Read the FACTORY manual. (what did you think it stood for?!?)

If you do read it, you will learn what is and is not recommended. Lots of good info in there. I can see why you might think venting could be required... and venting is (in general terms) not a bad idea for high flying rockets that experience a large change in air pressure as they reach a high altitude.

Anyhoo... check this out - https://www.jollylogic.com/wp-content/uploads/2015/12/JollyLogicChuteReleaseWeb.pdf

 

[Tobor]

Not necessary. Vent holes are only needed for devices that sense atmospheric pressure while in the rocket. The altimeter portion of the JLCR senses atmospheric pressure and releases the pin, rubber band, and chute at your programmed elevation while free falling after ejection.

Best invention ever. I'm still waiting for the JLCR II that can fit inside a BT-20 tube.

FWIW, Twice I have used the CR in my 3" BlackFly. On the 2nd flight with CR set to 600', my JLCR had popped at apogee.

Why you ask?

Well, I had been warned b4 that flight to install the motor after I had prepped my rocket to avoid tricking the CR into believing a flight event had occurred. But while my rocket was on the pad, I was not sure if I had turned on my CR so I had to remove it to verify. It was on btw. Apparently, rockets with tight fitting nosecones (I had previously increased the friction on mine for my L1 attempt), cause a problem with JLCRs when one preforms a assembly/dis-assembly/re-assembly of the rocket with motor installed. Luckily for me, the wind was blowing the rocket towards the flight line.

I now know that with the addition of any electronics to an MPR/HPR rocket, one should always use a "Printed" checklist. Too many things going on at larger club launches to mentally keep track of it all.

 

[tOD]

As a novice I was mostly concerned with proper chute packing. I noted the advice about closing up the rocket before 30 sec. to avoid a pressure spike when fitting the pieces together, so I made a few practice runs. I did notice a little scorching of the tether however, and I think I'm going to replace it with Kevlar, and probably use a larger Nomex blanket next time. All in all a great little device.

 

[snrkl]

Do you think a JCR for BT20 size rocket would be a big seller for John? A $129.00 item in a $20 rocket.

I’d love one that fits into my 29mm MD...

I’m planning an H and I versions for Thunda Downunder next year and they are getting too big for streamer recovery.

And the $20 rocket has $300 (JLCR and EFMini) of electronics and motor cases in it, so yes, I’d spend more on it to bring it closer before main deployment.

 

[snrkl]

I didn't see anyone else state the obvious... so here goes -

When in doubt, RTFM. Read the FACTORY manual. (what did you think it stood for?!?)

If you do read it, you will learn what is and is not recommended. Lots of good info in there. I can see why you might think venting could be required... and venting is (in general terms) not a bad idea for high flying rockets that experience a large change in air pressure as they reach a high altitude.

Anyhoo... check this out - https://www.jollylogic.com/wp-content/uploads/2015/12/JollyLogicChuteReleaseWeb.pdf

Yes. Vent it. I’ve seen the JLCR take the NC going on as a pressure change that then triggered the release on the pad. (Fortunately we heard the servo and it release on the pad as my club mate was doing it) - quick cordless drill vent hole and all good.

 

[JSW]

Has anyone used a small drone chute (at time of motor ejection), paired with a bigger chute released by a JLCR (at a lower altitude)?

 

[David Schwantz]

Yuppers. 1/52nd Saturn V with a 30" drogue and a 9' main just beginning to deploy after JLCR released.

 

[SolarYellow]

Best invention ever. I'm still waiting for the JLCR II that can fit inside a BT-20 tube.

BT-20, unlikely. BT55, I'd buy it. My magician is still susceptible to loss on E's. And if it works on BT55, would it not work on 4" airframes also?

I’d love one that fits into my 29mm MD...

And the $20 rocket has $300 (JLCR and EFMini) of electronics and motor cases in it, so yes, I’d spend more on it to bring it closer before main deployment.

I would buy one for sure if it worked in a 29mm tube. No real interest in anything more than a BT-55. But even at that point, there's going to be at least an Eggfinder Mini on board if it's going high enough for dual deploy. Not to mention all the man-hours to get the EFM installed (sled construction, etc.) and the rocket built.