LOC Doorknob Question

Discussion in 'High Power Rocketry (HPR)' started by Balsa Bob, Jun 4, 2016.

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  1. Jun 4, 2016 #1

    Balsa Bob

    Balsa Bob

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    Hi all,

    I seem to have misplaced the instructions... if you've built this kit, can you tell me how far from the top of the MMT the upper CR is to be affixed... 1/4-inch or so?

    Thanks in advance.
     
  2. Jun 4, 2016 #2

    cavecentral

    cavecentral

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    Not sure on the instructions, but 1/4" to 1/2" is what I usually do on my rockets in general. As long as any fin tabs are not blocked by the rings, you should be good.
     
  3. Jun 4, 2016 #3

    Balsa Bob

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    Thanks, cavecentral... I ended up going with 3/8" and added a nice fillet.
     
  4. Jun 4, 2016 #4

    grouch

    grouch

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    Just need enough room at top for the fillet.
     
  5. Jun 4, 2016 #5

    Balsa Bob

    Balsa Bob

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    Agreed, grouch...
    After eying that big nosecone shoulder I started wondering if there would be enough space for the laundry.
    I'm glassing tip-to-tip now and all is coming along nicely.
    Thanks.
     
  6. Jun 4, 2016 #6

    Pyropetepete

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  7. Jun 4, 2016 #7

    neond7

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    Post some pics of your build! I definitely recommend upgrading the bent hook eye bolt with a stainless u-bolt as its a heavy kit.

    I glassed my LOC Doorknob air frame and did tip to tip fiberglass on the fins as well. I also added an avionics bay and payload section to make it dual deploy. It flies regularly on 54mm 6XL CTI "L" impulse motors, one day I might build another one with a 75mm mount and fly it on an "M".
     
  8. Jun 4, 2016 #8

    Balsa Bob

    Balsa Bob

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    CR u-bolt.JPG Nosecone eyebolt.JPG Tip to tip.JPG
    I opted for an eyebolt and u-bolt for nosecone and CR, respectively, and glassed the BT and fins. First flight will be on a J350W.
     
  9. Jun 6, 2016 #9

    neond7

    neond7

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    Looking awesome!! With the fiberglass, those fins will be nicely locked in.

    Here is a pic of mine from last month. It went on an L805w to 4,100'.

    ImageUploadedByRocketry Forum1465177416.127656.jpg

    ImageUploadedByRocketry Forum1465177366.005183.jpg
     
  10. Jun 6, 2016 #10

    samb

    samb

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    Good call. Great minds think alike ! :)

    IMG_0141.jpg IMG_0411 (2).jpg IMG_0413.jpg
     
  11. Jun 6, 2016 #11

    Balsa Bob

    Balsa Bob

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    Beautiful paint job... and an outstanding L3 build thread...!
     
  12. Jun 7, 2016 #12

    samb

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    For mine I have about 11 1/4 inches of laundry space: 16 inches from the forward CR to the top of the airframe minus about 4 3/4 inches taken up by the nose cone shoulder. What did you come up with ?
     
  13. Jun 7, 2016 #13

    Balsa Bob

    Balsa Bob

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    I'll have to check the internal dimensions tonight after work. Here're two photos - ready for final primer coat:
    Doorknob BT.jpg Doorknob NC.jpg
     
  14. Jun 27, 2016 #14

    Balsa Bob

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    The Doorknob flew at MDRA this past Saturday on a J350... gonna drop down the chute size as it drifted a bit.
    IMG_0795.jpg

    Link to the video:
    https://youtu.be/N5QNIeD5j6s
     
  15. Jun 28, 2016 #15

    jef955

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    I love the Doorknob.. I flew mine on a J350w for my Level 2..

    1467077741982.jpg
     
  16. Jun 28, 2016 #16

    Balsa Bob

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    Nice looking Time Bandit, jef955... I'm very happy with the kit and, IMO, the artwork on the LOC website doesn't do it justice. Dunno know why, the but lines are noticeably sleeker in person. Now I'm thinking of dusting off my Defy Gravity Tether and boosting on a "K" motor.
     
  17. Jun 28, 2016 #17

    jef955

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    Balsa Bob what size chute did you use ? I used a 72" liftoff weight 152 ounces... I considered cutting to 60, but I popped a fin fillet when a gust of wind kinda picked it up just before it touched down.
    To the OP - I set my centering ring 1/4 inch or so below tge end of the motor mount tube, and had room for everything with no troubles..
     
  18. Jun 28, 2016 #18

    jef955

    jef955

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    And I also fly with MDRA, didn't make it this weekend though - damn Bronchitis!
     
  19. Jun 28, 2016 #19

    Balsa Bob

    Balsa Bob

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    Hi jef955,
    My Doorknob exceeded LOC's advertised weight of 122 ounces before I even laid down the primer... coming in at ~175 ounces fully loaded - The 60-inch stock chute was undersized, but the next larger chute I had on hand was 84-inches, so that's what I used. I've since ordered a 70-inch chute from Top Flite which should be about right. Also, there was plenty of room above the upper CR - that 7.67 airframe is very spacious!
     
  20. Jun 28, 2016 #20

    jef955

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    Yeah, more than enough room.. I didn't cut or shift anything and still had plenty of space..
     
  21. Jun 28, 2016 #21

    Balsa Bob

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    My first 4-inch build seemed huge at the time - I could fit my hand and arm inside the airframe. The 7.5-inch builds have been terrific, but I'm running out of room for them. I may have to limit myself to 5.5-inch BTs...:(
     
  22. Jun 28, 2016 #22

    ThirstyBarbarian

    ThirstyBarbarian

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    My first 4-inch airframe was a revelation --- it is VERY convenient to be able to put your arm into the airframe. The 7.5-inch birds are a pain to store, but the real problem is the fin span as much as the tube size. Even the 4-inch Mega Der Red Max is a bit of a pain with the wide fins.

    I have a Warlock (Doorknob's shorter brother), and it is a really fun rocket to fly.
     
  23. Jul 1, 2016 #23

    jis2

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    My original hook into this hobby was to witness a Warlock on a J-570 !! Awsome rocket and flight !
     

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