Should I use the chute release on my L2 flight?

Discussion in 'The Watering Hole' started by Jdog13, Aug 9, 2018.

  1. Aug 9, 2018 #1

    Jdog13

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    I'm doing a loc patriot 5.5" on a J430. Should go about 2300'-2500'. The chute is 52 inches. I have a chute release, but I'm not sure if I should use it on this flight. It hasn't failed me in the past, but I guess it is one more item that could go wrong during the flight. I have never flown a rocket this heavy before (7-8lbs) so I don't know how far it will drift.
     
  2. Aug 9, 2018 #2

    llickteig1

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    If your recovery area is large, I would not use the chute release for just the reason you state - it is one more failure point. At that altitude with the large 'chute you will be able to see the entire flight, no problem. If it is windy, you might consider the CR, though.

    A suggestion: use a tracker, despite likely visual all the way down. It just makes recovery so much easier.

    --Lance.
     
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  3. Aug 9, 2018 #3

    davdue

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    Depends on the winds at your launch location. 52" seems like a good size for that rocket. As far a using the chute release for your launch. It isn't anymore prone to failure than any other electronics. As long as you set it up correctly then all should be well. If you launch location has trees and other obstacles that drift could be a problem for I would definitely use the chute release.
     
  4. Aug 9, 2018 #4

    BDB

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    I did it with a 48" chute. I used two chute releases that were hooked to each other to provide redundancy. Worked like a charm.
     
  5. Aug 9, 2018 #5

    K'Tesh

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    While I haven't done that, I'm planning on doing the same thing (2 JLCRs) with my L2 flight.
     
  6. Aug 9, 2018 #6

    Jdog13

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    That is a great idea, If only chute releases weren't $130 a pop.
     
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  7. Aug 9, 2018 #7

    Keisling

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    I don't really see a big deal with using a CR for a cert flight if you normally use one (sounds like yo do). I used one for my level one flight simply because I used it in every prior flight of that rocket. Omitting the CR for the cert flight would have been a change from what I was accustomed to and I saw that as a greater risk than the "one more failure point" of using the CR.
     
  8. Aug 9, 2018 #8

    dshmel

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    If you use a JLCR, I suggest you set it for 100' to 200' higher than your target deployment altitude. All of the JLCR flights I have seen (including mine) have always deployed at what appears to be a lower than set altitude. The last JLCR flight was set for 100', and deployed just before impact. I have also not "cracked the code" yet on bundling the chute and wrapping the rubber band. I have gotten numerous failures where the rubber band binds into the chute as it snaps back upon release. I have tried wrapping the rubber band around the chute protector and have still had failures.
     
    Last edited: Aug 10, 2018
  9. Aug 9, 2018 #9

    PokerJones

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    You have to keep in mind that the CR "releases" at the specified altitude, falling at 50-60 fps it is going to take a few additional seconds to unfurl and deploy which could easily be a few hundred feet.
     
  10. Aug 9, 2018 #10

    T-Rex

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    The only failure that I have had using a chute release was my own doing. As soon as I picked up the wreck, I realized my mistake.
    As was said above, if you normally use one, and you are using it successfully, then by all means use one for you cert flight. Stick to your routine, things usually go better that way.
     
  11. Aug 10, 2018 #11

    Jdog13

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    Yeah I would probably set it at 700-800'. Another thing I just thought of is about the shock of the parachute opening. I don't have a drogue for this so the heavy rocket would fall quickly and then suddenly slow down. Im using the stock 25' nylon cord it comes with, which is not very elastic. When the chute finally opens I'd be worried that it rips the cord or zippers the tube because of how heavy it is with little elasticity to dampen the shock.
     
  12. Aug 10, 2018 #12

    dshmel

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    Understood. My assessment is based on when I visually see the release activate. I have not tested a chute release in a vacuum chamber with other flight controllers to see if it consistently activates "late". Rather, based on first hand observations, I set my JLCR for 100' to 200' above the target altitude that I want the release to activate, with the assumption that the chute takes 50'-100' to unfurl and fill, and other 100' (or more) to slow to the rocket to the terminal main chute descent rate.
     
  13. Aug 10, 2018 #13

    matthew

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    There is nothing at all special about a certification flight beyond some extra paperwork. If you fail for some reason, the penalty is having to fly another rocket. You were going to do that anyway, right? :)

    Do what you normally (successfully) do and enjoy flying rockets.
     
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  14. Aug 10, 2018 #14

    Bat-mite

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    That's my answer, too.
     
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  15. Aug 10, 2018 #15

    Steve Shannon

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    Exactly! Cert flights are no place to try a bunch of new things you’ve never done before. It should be just another flight to demonstrate what you know, but with a bigger motor.
     
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  16. Aug 10, 2018 #16

    dr wogz

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    I did my L2 with a JLCR. but then again, I've done my L2 rocket & chute (with JLCR) a few times, so I was comfortable with it working. (Nothing says the rocket has to be a new, virgin rocket. Only that you built it..)
     
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  17. Aug 10, 2018 #17

    pondman

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    I have signed-off on a few L1 & L2 certs with the JLCR. No issues and it saved the flyer a long walk.
     
  18. Aug 10, 2018 #18

    Bat-mite

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    I must say, I have seen more than one cert attempt, usually level 1, where the candidate launches to a ridiculous altitude, pops the main at apogee, and then watches his rocket drift beyond the farthest trees. Getting an HPR cert isn't just about launching with a bigger motor. It is also about how to fly your field, how to control descent, how to recover your rocket....

    I know that at MDRA's summer sod farm launches, GPS and DD are a must. There is a building right in the middle of the field. There are woods right in front of the pads. And there is a river about a 1/4 miles behind the pads. There is also at least one irate neighbor that won't return rockets. I want my birds coming down as close to the pads as possible.
     
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  19. Aug 10, 2018 #19

    dshmel

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    Well put ↑
     
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  20. Aug 10, 2018 #20

    Steve Shannon

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    I agree with what you say, but none of the techniques or technology you mentioned should be introduced to the flyer during a cert flight. That’s why I stand by my statement that the only thing new to the flyer should be the motor size.
    That’s not a rule (nor should it be) but it is the best way to succeed in a certification.
     
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  21. Aug 10, 2018 #21

    markkoelsch

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    A cert flight is to prove you know what you are doing at a certain power level. Whether this is a simple L1 flight using motor deploy, all the way to a L3 with redundant electronics using dual deploy that statement stands. It is not the time or place to introduce technology/techniques you have not used before.

    So, to the OP. If you have done a few flights with the JLCR and are comfortable then do it. If you have not done a few flights on it I suggest doing a couple flights on L1 motors using the JLCR first.
     
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  22. Aug 10, 2018 #22

    Bat-mite

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    OP stated in the OP that his JLCR "hasn't failed me in the past." He is not introducing anything new into his cert flight. I think sometimes people read the subject and not the message.
     
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  23. Aug 10, 2018 #23

    Steve Shannon

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    You’re right; he did say that. I had forgotten since reading his first post.
    If he feels comfortable using the JLCR and if the field size or wind speed create undue constraints, using the JLCR makes perfect sense.
    He should simply fly what’s familiar.
     
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  24. Aug 12, 2018 #24

    Buckeye

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    I saw his mentioned a couple times in other threads, but I can't picture this chaining of two JLCRs. Can you explain? What are you guarding against with this redundancy?
     
  25. Aug 12, 2018 #25

    dhbarr

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    JLCR,PIN,BAND,JLCR,PIN,BAND

    The thinking goes that since they're in series if either fails to activate or gets bound, the other should open and allow the chute to unreef.
     
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  26. Aug 12, 2018 #26

    mperegrinefalcon

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    I personally don't particularly trust the JLCR. I would use a cheap altimeter like an RRC2+ or RRC3 for apogee deployment or DD. I have seen too many of the things turning off on the pad and then failing to deploy. I saw it on a couple of certification attempts. My L2 was DD with 2 altimeters set up for redundancy. It isn't particularly hard to implement DD, but if you want to practice it then set up a smaller rocket on an H or an I and have it be dual deploy. For first time DD, the RRC3 or RRC2+ are great systems that are super easy to use and set up. You can just use the switches on them to set altitudes and the instructions are very concise and clear.
     
  27. Aug 12, 2018 #27

    dhbarr

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    I have seen a lot of folks make mistakes with the JLCR, but not a whole lot of actual JLCR failures.

    It is very tempting, because of how straightforward it is, to not spend enough time practicing ( for example ) how the tether interacts with the canopy.

    My two failures involved folding badly thus binding the sheet; and setting too low an opening height then landing in a tall tree on the top of a hill.
     
  28. Aug 17, 2018 at 2:52 AM #28

    woferry

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    I've only had two 'failures' with my JLCRs, but both were safe failures. Once the band broke at apogee (I think because the shroud lines were too loose compared to the short tether I had connecting the CR), and once the CR seemed to have released inside the airframe (I think due to removing my NC after the CR was already on, at the RSO's request). So both landings were on main, just a farther walk than I'd hoped for. I did get to the pad once without having powered-up the CR, but realized my mistake when going over my pad checklist, so I pulled the rocket off the pad and corrected it before flying (and now put a tape label on the airframe to help remind myself when any of my chutes aren't totally ready to fly, as I was starting to pre-pack my chutes to get more flights in, and that would have obviously been a bad step to miss).
     
  29. Aug 17, 2018 at 2:53 AM #29

    woferry

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    EDIT: Oops, got a server error and it wound up double-posting.
     
  30. Aug 17, 2018 at 2:44 PM #30

    BDB

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    Here’s a pic of the setup (using a different chute). The two JLCRs are attached in series, so if one fails, the other still opens the chute. It’s probably overkill, but I wanted the insurance for my cert flight.

    5D581491-7AC9-4659-B528-3CDC66B5FF02.jpeg
     
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