38mm Kit opinion need for dual deployment

Discussion in 'High Power Rocketry (HPR)' started by spigalau, May 13, 2019.

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  1. May 13, 2019 #1

    spigalau

    spigalau

    spigalau

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    Hi,

    1st time poster, occasional lurker.

    Looking for advice & recommendations for building a 38mm powered dual deployment rocket with my son.

    We have figured out:
    * 38mm - gives options for running G through to J
    * Dual deployment - drogue or streamer & main - we are sick of long recovery walks...
    * Electronics - Dual StratoLoggerCF Altimeter or similar
    * 3" frame

    Our intention is to build something that is:
    1) Cost effective to fly (G)
    2) Initial Goal - Able to achieve L1 certification (H & I class)
    3) Secondary Goal - Able to achieve L2 certification (J+)

    Our current thought is the MPR 38 - 3" but open to suggestions.

    Being in New Zealand, we have a limited supply of motors/reloads available - a 38/720 RMS case would give us ability to do a J launch, but case would extend in to lower bay by about 3cm - would this have any negative impact ? Would using a single use J class motor be better for L2 cert, which would also protrude in to the bay ?

    or should we initially limit ourselves to a 38/600 case and by using a 38mm reload adapter system, load it up with smaller charges for initial G, H or I launches ?

    Thanks in advance.
    Spig.
     
  2. May 13, 2019 #2

    dhbarr

    dhbarr

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    It'd be hard to go wrong with Mac Performance, and 38/3in is a great looking kit.

    i600r and j500g are extremely similar loads in the 38/720.

    Have you played around with it in OpenRocket yet? I think it's a fine choice.
     
    gfunk likes this.
  3. May 15, 2019 at 5:33 AM #3

    Kosmo

    Kosmo

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    Consider the Peregrine kit from Apogee. It's a pretty big but easy to build rocket marketed for those starting out in dual deployment. Apogee recommends not using it for certification specifically because they don't recommend dual deployment for cert flights. That said, it can be configured for single deployment easily if you want to go that way.
    It can fly on G motors (not very high) and yet it's long enough to accommodate 38mm J motors.
     
  4. May 15, 2019 at 6:52 AM #4

    amiliv

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    For my L1, I decided to keep it simple and experiment with dual deployment as separate project. Relatively short 4" rocket flown on H motor will be short walk to recover. I actually had two such rockets with me on my cert day. Estes Mega Der Red Max (29mm MMT) and LOC Goblin (54mm MMT). I did my cert flight with Mega Der Red Max on an single use AeroTech H182R that took it to 1400 feet (425 meters). The Goblin is very versatile rocket that'll fly on a wide range of motors, from 29mm all the way up to 54mm; though one needs to keep an eye on weight while building it if the goal is to not exceed 1500 grams fully loaded with F and G motors (mine ended up a bit too heavy, even with an F motor it'd be over 1500 grams).

    For experimenting with dual deployment, I'm just finishing a 3" LOC Iris that I bought with optional avionics bay. My first choice was actually 3" LOC Sandhawk, but they were out of stock at the time. There's plenty of great 3" and 4" dual deployment kits out there. A 4" kit might be bit more maintainable, as I can't reach inside 3" airframe, but I can reach inside a 4" airframe.
     
  5. May 15, 2019 at 6:56 AM #5

    mpitfield

    mpitfield

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    Ah someone who appreciates wine. I would consider the 4" MAC Performance BlackFly. With the canvas airframe it will be light enough to fly on 38mm motors, using a 54-38mm adapter. But more importantly it will give you a lot of real estate for recovery systems and a lot more motor options, if you decide to use it for your L2.

    Ideally you would use one rocket for your L1 and one for your L2. If so you can also look at the 3" MAC BlackFly, for the L1.

    BTW the I600 Red Line packs one heck of a punch, it is one of my fav motors but it will send your 3" airframe to a mile AGL @ .8 Mach. Not an issue for the rockets we are discussing but not exactly a safe pop and drop cert, which most people will recommend...but not me.

    If you go Peregrine CO2, keep in mind that it is more finicky to dial in, so go the distance when it comes to ground testing. I am a big fan of electronic ejection but using CO2 over BP is a bit more challenging.
     
  6. May 15, 2019 at 6:01 PM #6

    jqavins

    jqavins

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    One thing nobody answered is you question about the motor overhanging the MMT. It's no big deal in general, and at 3 cm it's no issue at all.

    I've got a dual deploy rocket mostly built for my L2 attempt (one of these months) but after reading some good arguments I'm thinking I might cert without that, or with a Jolly Logic Chute Release, and take on dual deployment later (with the same rocket).
     
  7. May 15, 2019 at 6:34 PM #7

    ouisconsin rocket

    ouisconsin rocket

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    I built the Apogee Peregrine for exactly the same reasons you are looking at. I did my Level 1 using an AIM USB dual deploy altimeter and all went without a hitch. Hardest part of the build was getting the epoxy off my fingers. Great instructions and easy to follow assembly. Ready for Level 2 with the same setup, albeit a larger motor.
     
  8. May 15, 2019 at 7:06 PM #8

    amiliv

    amiliv

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    Yup. One can play with dual deploy even on mid-power before going for L1. But neither L1 or L2 requires it for certification flight. Said that, I've heard more than once that having experience with dual deployment is something that people like to see from you before flying that L2 certification flight. Even if you plan to fly something simple like 7" LOC Warlock for the L2 cert.
     
  9. May 16, 2019 at 12:08 PM #9

    David Schwantz

    David Schwantz

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    All of Mach ! kits are great. You can fly them DD like you want or you can install steel 2-56 instead of shear pins and remove the guts of the AV bay and fly motor eject.
     
  10. May 16, 2019 at 5:15 PM #10

    amiliv

    amiliv

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    I think OP said he lives outside of US. US screw sizes are, well, very US specific and in some countries can be hard to find. If a much younger me who grew up outside of the US was told to use #2 screw for something, I literally wouldn't know how big (or small) that screw is, and not a single store where I lived was selling those. I wouldn't be able to look it up or order it on Internet either, because there was no Internet back then.

    #2 screw has 2.184mm diameter, and 56 TPI is about 0.454mm thread pitch, so probably something like standard M2 screw with coarse (0.4mm) pitch might be much easier to get...
     
  11. May 16, 2019 at 5:50 PM #11

    David Schwantz

    David Schwantz

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    Point being, replace plastic with steel!
     
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