PML 3" Bull Pup

Discussion in 'High Power Rocketry (HPR)' started by AfterBurners, Jan 28, 2020.

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  1. Jan 28, 2020 #1

    AfterBurners

    AfterBurners

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    I just ordered PML's 3" Bull Pup kit. I'm looking forward to the build. I had one before and ended up selling it on here, the reason I should of used a cleaner looking retainer, like the Slimlines that GLR sells. Also instead of going with the nylon shock cord with the kit, I'll pick up a pre-sewn nylon cord from Topflight and use quick links as attachment points. I'm still going to go with the piston ejection system. I think its a cool concept. I'll lay down a really smooth paint job and get some custom decals made from Stickershock.

    It seems once you build a kit once you learn so the next time it turns out much better!
     
  2. Jan 28, 2020 #2

    crossfire

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    Make sure we get to see pictures. It should be a fun build.
     
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  3. Jan 28, 2020 #3

    AfterBurners

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    For sure!
     
  4. Jan 29, 2020 #4

    mpitfield

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    I used the GLR Slimline on mine. IMO it is a nice look. It could have been recessed further into the tailcone but this worked well.

    20140503_001135Small.jpg
     
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  5. Jan 29, 2020 #5

    AfterBurners

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    Nice work. I plan on recessing it all the way in. Quick question? How did it fit on the PML motor tube? Was it a close fit? I was considering just buying on of their motor tubes so I know I'll get a solid fit. I was also considering getting an extra nose cone to see how much actually needs to be removed to tuck the entire assembly into the boat tail. Based on your photo without actually having the parts in front of me, would you say if you cut maybe 1/4" more off the end the slimline retainer would be completely tucked into the boat tail?
     
  6. Jan 29, 2020 #6

    mpitfield

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    I don't recall if I had to use some small pieces of tape placed 120° apart, or if it was snug enough on the MMT to just J-B Weld, as is. Below is a picture I took just before I installed the retainer. Regardless, the retainer is firmly installed, so I wouldn't be concerned or bother ordering another MMT unless you need it for something else.
    CAM00128CroppedSmall.jpg
    Again, I don't recall. However, it would depend on several things. How much you want the retainer to extend outside the tailcone, how thick the tailcone wall is and the taper of the tailcone. Below are before and after pics of my MAC CF Rainmaker. This is a 54mm rocket, so it has less taper to work with that results in having to remove more material to recess the retainer. I don't recall how much I removed, but, from the pics, it looks like roughly 1". I would take some measurements of the O/D and the wall thickness. Using those measurements, you can estimate where the cut needs to be. From there, I would be conservative with your cut. The biggest issue is that these tailcones (trimmed nosecones) are not uniform in their thickness.
    IMG_20171018_223645.jpg IMG_20171022_180300_01.jpg
     
  7. Jan 29, 2020 #7

    rcktnut

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    Bullpup -retainer.jpg DSCF0002.JPG I used the Aeropack retainer and liked the way it looked. I understand you want the retainer completely hidden inside the boat tail. To get the cut on your boat tail you could insert the retainer on the MMT insert the assembly in through the top of the boat tail, put on the centering ring to straighten out and measure up from the bottom to where the retainer has stopped inside the boat tail. That or maybe a bright light might show where the retainer is and you could directly mark it on the outside. Good Luck, looking forward to pics.
     

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  8. Jan 29, 2020 #8

    AfterBurners

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    Nice work!!
     
  9. Jan 31, 2020 #9

    AfterBurners

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    Anyway I exchanged some emails with Bob @ GLR. Really a great guy and very helpful. Quick to answer emails and unfortunately it looks like I will have to think of a different retainer or fashion something of my own. The thing with slimline retainers is that they don't accept other manufacturers motor adapters, only their own. I'm not going to spend $35 on a retainer and have to spend $27 more for an adapter when I already have a complete set of AP retainers. Who knows maybe I'll just go with friction fit or design something?
     
  10. Jan 31, 2020 #10

    mpitfield

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    An adapter is relatively inexpensive and easy enough to make.
     
  11. Feb 1, 2020 #11

    AfterBurners

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    IDK I'm still kicking it around...I really want a clean appearance on this build....maybe I'll bite the bullet and fork out the cash.
     
  12. Feb 25, 2020 #12

    AfterBurners

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    This is also very nice. I'll probably go with this configuration
     
  13. Feb 26, 2020 #13

    grouch

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    FYI, I use an Aeropack 29mm adapter in a Slimline 38mm retainer all the time.
     

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