Anyone Mod a Big Bertha

Discussion in 'Low Power Rocketry (LPR)' started by Klatuso, Jun 7, 2018.

  1. Jun 7, 2018 #1

    Klatuso

    Klatuso

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    I'm considering getting the classic. I am a looking to reinvent the basic big rocket. Looking for color schemes, added fins, techniques for larger engines; anything you have done beyond the basic directions. If you could build this bird again what might you do differently?

    Things I just tried are the replaceable shock chord wrapped around the rear motor mount, papering fins (yea, just tried it), epoxy for future larger engines.

    Have you tricked this rocket out with fancy paint? Pictures would be most helpful. Steampunk? Have at it!
     
  2. Jun 7, 2018 #2

    Gus

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  3. Jun 7, 2018 #3

    RocketFeller

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    Look into a Super Big Bertha- it is the most fun you can have on a D12-3!
     
  4. Jun 7, 2018 #4

    Rex R

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    hmm, lets see...24mm mount, 38mm mount(1 grain), payload section & 24mm mount, and a two stage version(note; booster should have a 24mm mount).
    Rex
     
  5. Jun 7, 2018 #5

    milehigh

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    I'm really liking that BerthaVostok !
     
  6. Jun 7, 2018 #6

    jnobels

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    I’ve actually been thinking about a “sleeper” version of this. Scratch build with a 29mm mount, plywood through wall fins, and thick wall tubing. Might as well go all the way...
     
  7. Jun 7, 2018 #7

    Steve Shannon

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    I made a 38 mm minimum diameter version. It came about sort of by accident. I was teaching a young friend how to glass tubes and grabbed the Big Bertha body tube. Then I peeled the outer layer off a motor mount tube in order to glue it inside (nearly full BT length up to the nosecone). I started glassing the fins but my interest kind of petered out about there because I didn’t think I should try to fly it, believing that the fin design is likely to flutter. I keep it (and several other things) around as a testimonial to my frequent idiocy.
     
  8. Jun 7, 2018 #8

    DankMemes

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    I've been saving this until she's built but what the hell, as I have all the parts, just waiting for a free weekend to assembly her.

    As Bertha's big butch sister, her name is Angry Alice

    Spec's
    24mm Motor Mount (With E-Size Retaining Ring, and upgrade to plywood centering rings)
    Rocketarium Ejection Baffle
    TTW Plywood Fins
    Apogee Strap on Booster Set
    20g clay ballast in the nose



    Since its all off he shelf components sans the fins which I'll need to cut, is should go together pretty quickly.

    Planning for a dramatic launch with an AT E6-6 main motor for a nice long duration burn, that one each C6-0 in each booster. Should put on a good show with a long burn even after the boosters have separated.

    Thoughts?

    Alice Wireframe.jpg

    Alice Render.png

    View attachment Angry Alice.rkt.zip
     
  9. Jun 7, 2018 #9

    PhlAsh

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    Double-D Bertha (aka Bertha's Bosom Buddy)
    My Breast Cancer Awareness rocket.
    2 24mm MMTs
    Dual Tassle recovery

    DoubleD_Bertha.jpg Picture 36.jpg
     
  10. Jun 7, 2018 #10

    Daddyisabar

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    Here are some Baby and Big Bertha modifications, or at least they started as Bertha kits. No limit to the modifications and kit bashes.

    P9140001.jpg P9140002.jpg PA050004.jpg PA050002.jpg PB030039.jpg P1130075.jpg P3100165.jpg 169.jpg P5030228.jpg P4300217.jpg

    Lookup Goonies - modified Baby Berthas. Just take your Bertha and start adding stuff. Who knows what you will come up with.
     
  11. Jun 7, 2018 #11

    Rex R

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    perhaps I should mention that aside from papering the fins, the fins are otherwise stock surface mount. paper centering rings were also used. folks seem to under estimate the strength of their building materials. the 38mm Wild Bertha landed about a 1/2 mile down the road...undamaged :).
    Rex
     
  12. Jun 7, 2018 #12

    hcmbanjo

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  13. Jun 7, 2018 #13

    hcmbanjo

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    duplicate post
     
  14. Jun 8, 2018 #14

    brewster_rockit

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    I'm building my Bertha with Astron Ranger motor mount, #4 machine screw for the motor retainer. Kinda pointless since D motors are widely available, but the extra thrust is impressive. Not doing the Ranger payload bay since I don't have any payloads in mind. Considering a Super Big Bertha paint scheme but might change my mind.
     
  15. Jun 8, 2018 #15

    caveduck

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  16. Jun 11, 2018 #16

    hermannj

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    I just opened mine and I can’t believe how thin the body tubes are.
     
  17. Jun 11, 2018 #17

    rharshberger

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    If worried or you want it stronger ( but heavier) you can double tube the airframe using a full length coupler from BMS.
     
  18. Jun 13, 2018 #18

    caveduck

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    Another tube solution is to substitute .020 heavy wall tubes from Discount Rocketry, but the nose OD will be a bit smaller than the tube OD.
     
  19. Jun 14, 2018 #19

    Mushtang

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    I did a mod on the launch lugs. I built up the sides with CWF and sanded them smooth so that the lugs are now a bump in the side of the body.

    [​IMG]
     
  20. Jun 15, 2018 #20

    RocketFeller

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    They are very thin, but that is how it can fly on a D12. If you beef up the tubes much you will be needing E or F power. I hardened the forward end with thin CA and it seems to be holding up well. We have done seven flights so far and it is still in good as new condition.
     
  21. Jun 15, 2018 #21

    shreadvector

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    Arrivederci

     
  22. Jun 15, 2018 #22

    Zeus-cat

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    Technically it is Vega, but close enough. I planked it with very thin strips of wood and call it Ye Olde Amish Rocket. It even has an outhouse for a launch lug.

    [​IMG]
     
  23. Jun 15, 2018 #23

    hermannj

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    Love these!
     
  24. Jun 15, 2018 #24

    Rex R

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    Loc 38mm motor tube has an od just a hair smaller than bt60.
    Rex
     
  25. Jun 16, 2018 #25

    Eric

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    This one has two wraps of 7 oz glass and fiberglass fins. Should handle and 29mm thrown at it. Just needs a lot of filling and sanding. It will be a sleeper in stock paint. Anyone have unused Bertha dacals laying around? 0615181732.jpeg
     
  26. Jun 16, 2018 #26

    BABAR

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    1DA9A4C1-43E8-4A9B-82A8-F6FBD25FD072.png 56708E3B-89FF-4BC9-808A-F5706CA206FB.jpeg Kevin?
     
  27. Jun 22, 2018 #27

    jqavins

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    I haven't built it, but I think I did the exact same RockSim design.
     

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