Jolly Logic Chute Release as a dual-deployment method

Hi everyone,

First of all, I am trying to post this thread in the chute release forum, which is where it is supposed to be. I don't understand how to do that, however.

Now that I have said that, let me ask my question please.

I am considering buying the Jolly Logic Chute Release (JLCR). As I understand it, you set the altitude at which you want the parachute to open. By properly configuring the JLCR and correctly packing the parachute, the JLCR will cause the parachute to open at the desired altitude. I think that I have this correct.

So here is my question. In essence, using the JLCR is a form of dual deployment, right? Instead of a drogue parachute's or a streamer's being deployed at apogee, however, nothing is deployed. Thus, presumably, the entire rocket begins a rapid descent but a descent that occurs not far from the launch site. (This of course is the purpose of dual deployment -- the rocket does not undergo a long downrange distance.) Then, at the desired altitude the JLCR triggers the deployment of the parachute.

To summarize my question, therefore, could it not be argued that by using the JLCR, you are engaging in a fairly easy method of dual deployment? Does this make sense, or am I way off the mark?

Thank you.

Stanley

You pretty much have all the bases covered.

A motor's ejection charge will pop the airframe open as normal. This breaks up the rocket's profile so that it doesn't return in a ballistic manner, but since the parachute is held closed, it will fall faster and drift less as you stated.

We use terms loosely around here (as I'm sure you've noticed), so calling it jolly logic dual deployment is heard often. Technically there's only one "deployment" by the motor charge, and then the chute is unreefed by the chute release (similar to using a cable-cutter, or hotwire release). Maybe "dual event" is more accurate, but I haven't heard anyone get nit-picky over it. If all goes well, it gets the rocket back closer to home, and that's what's important.

(This topic could go in either "Electronics and Software" or "Recovery")

The JLCR doesn't "deploy" anything it simply releases the chute to unfurl at a set altitude, the ejection charge for the motor or the altimeter is what does the deployment of the recovery gear. The JLCR is a great little device that works extremely well, used in the manner you stated it would act similar to a dual deployment event, though there is actually only a single event with a reefed chute (JLCR is the reefing device).

Deploy and a half is how I think of JLCR, hotwire, cutters, descenders, etc.

Nobody said both "events" had to be done by a single electronic system.

Only thing that might not be immediately obvious is that by opening the airframe and hanging out the laundry bundle, you've essentially deployed a bulky streamer.

dhbarr said:

Only thing that might not be immediately obvious is that by opening the airframe and hanging out the laundry bundle, you've essentially deployed a bulky streamer.

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Well stated, dhbarr. That makes a lot of sense.

As an alternative example of the loose definition principle I have described the use of the JL Chute Release as “delayed” deployment. There is one pyro event that separates the airframe with the deployment of the recovery device delayed until the designated altitude is reached. Dual deploy features two pyro events.

samb said:

As an alternative example of the loose definition principle I have described the use of the JL Chute Release as “delayed” deployment. There is one pyro event that separates the airframe with the deployment of the recovery device delayed until the designated altitude is reached. Dual deploy features two pyro events.

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Hi samb,

This is also a useful explanation.

Stanley

Nytrunner said:

Maybe "dual event" is more accurate, but I haven't heard anyone get nit-picky over it.

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Uh, see every pedantic post that followed this statement.

rharshberger said:

The JLCR doesn't "deploy" anything

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dhbarr said:

Deploy and a half is how I think of JLCR, hotwire, cutters, descenders, etc.

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samb said:

Dual deploy features two pyro events.

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de·ployment
/dəˈploimənt/
noun

1. 1.
   the movement of troops or equipment to a place or position for military action.
   "the authorities announced deployment of extra security forces in towns and cities to prevent violence"
2. 2.
   the action of bringing resources into effective action.
   "the rapid deployment of high-speed cable Internet services to consumers"

The OP is performing dual deployment.

Actually I find merit in all of the definitions offered here. If mine doesn't quite click with someone's sensibilities I would not be at all upset if it was cheerfully ignored.

Buckeye, I don't understand why you added the dictionary citation. Before the JL Chute Release, when the phrase "dual deploy" was used in model rocketry circles I always envisioned an electronic device that used pyro charges to deploy a drogue and a main, resulting in reduced drift and a shorter recovery walk. The JL Chute Release works differently to accomplish a similar aim so I thought a different shorthand was appropriate when describing it's operation. Delayed deploy works for me.

Make sure you tether the Chute Release to the rocket or parachute. I have heard of people losing them as they forgot, or didn't realize, that they had to do this.

Hi Buckeye,

Just so I understand your message completely, what does "OP" mean?

Thank you.

Stanley

MetricRocketeer said:

Just so I understand your message completely, what does "OP" mean?

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Original Poster

dhbarr said:

Original Poster

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Thank you, dhbarr.

Zeus-cat said:

Make sure you tether the Chute Release to the rocket or parachute. I have heard of people losing them as they forgot, or didn't realize, that they had to do this.

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I almost did this once so far. Luckily for me I ground tested the release and the JLCR fell to my feet. At which point I decided that I better attach it to the shock cord.

Just to add to the confusion, there is no need for any "pyro" events at all..Either can be activated by a pneumatic/magnetic/burn string (probably even hydraulic?) or even simply mechanical yet still be 2 separate deployment events. Most can also be achieved with a single break airframe. All a chute release is, is a reefing device with a controlled set point right?

Hi everyone,

One last question on the JLCR. Do you need to drill three holes in the air frame for that to work, the same way that you need to drill three holes in the air frame for the Jolly Logic altimeters to work?

Thank you.

Stanley

MetricRocketeer said:

Hi everyone,

One last question on the JLCR. Do you need to drill three holes in the air frame for that to work, the same way that you need to drill three holes in the air frame for the Jolly Logic altimeters to work?

Thank you.

Stanley

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Nope, I would drill a pressure relief hole though, that way as the nose cone is inserted or removed (slowly) it doesnt fool the armed JLCR into thinking the flight has started and cause it to open on the ground (it has happened to folks).

Hi Rich,

Then let me ask this question, please. I plan to insert a Jolly Logic altimeter along with the JLCR in the air frame. If I drill the three holes for the altimeter, will that simultaneously solve the issue of the pressure-relief hole?

Thank you.

Stanley

Yup.

[EDIT] As long as they are in the same contiguous airspace.

Depends. If your pressure relief hole(s) end up getting blocked by recovery stuff you may have a problem. Best way to find out is testing. Try putting everything together and see for yourself what happens. Relying on other's experience is a handy starting point, but commonly a road to disappointment. Testing leads to first hand knowledge that you can not only trust but also learn from.

dhbarr said:

Yup.

[EDIT] As long as they are in the same contiguous airspace.

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Contiguous is the key...

Hi everyone,

So just out of curiosity. How can the JLCR not work without holes in the air frame? How does the JLCR sense what the altitude is without these holes, in the same way that the JL altimeters require air holes?

Stanley

MetricRocketeer said:

Hi everyone,

So just out of curiosity. How can the JLCR not work without holes in the air frame? How does the JLCR sense what the altitude is without these holes, in the same way that the JL altimeters require air holes?

Stanley

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JLCR is usually out in the air stream after the motor ejection occurs (or altimeter fired ejection charge) so it knows where it is.

smugglervt said:

JLCR is usually out in the air stream after the motor ejection occurs (or altimeter fired ejection charge) so it knows where it is.

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Of course. I should have thought of that.

Baro only based units can be "fooled" by moving a nose cone or coupler since they "read" pressure. I've had it happen. Not sure if Chute Release has launch detect but would be simple to ground test. Again, first hand knowledge is always best.

Wallace said:

Not sure if Chute Release has launch detect but would be simple to ground test.

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Hi Wallace,

And how would you ground test this, please?

Thank you.

Stanley

A good, and also thoughtful question. What I personally would do is program and set it as if you were going to fly it. Then push the nose cone in/pull it back out and see if it has released, at least for starters.

Hi Wallace,

Good. A helpful answer. Thanks.

Stanley

I've had altimeters fail this test more than once....Not to imply they were "bad". You simply need to know how they work,,

Well, that would be a different test, right? How do you test an altimeter? Do you just check the altimeter reading for the altimeter sitting on the ground at a known elevation above sea level?