seeking: Centuri Bulldog plans

Discussion in 'Plans' started by GlenP, Mar 23, 2018.

  1. Mar 23, 2018 #1

    GlenP

    GlenP

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  2. Mar 23, 2018 #2

    kuririn

    kuririn

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    There's an old thread where someone drew up a Rocsim file for the Bulldog in order to clone it at the other forum. I think he wound up putting 24mm motors in it. Starts from post #63:

    http://forums.rocketshoppe.com/showthread.php?p=58733

    And here's the face card from Leo's:

    http://www.leo.nutz.de/images/rockets/bulldog.jpg

    Erockets has the nose cone:

    http://www.erockets.biz/semroc-balsa-nose-cone-bt-70-4-25-ogive/

    No luck on the Wayback Machine, but I only did a cursory search.

    If you have Rocsim, or know someone that does, you can get the length of the BT-70 tube and print a template of the fins (assuming that the file was drawn up accurately). Let us know if you clone this. Pictures, maybe a build thread?

    P.S. Found another old clone build thread on TRF:

    http://www.rocketryforum.com/showthread.php?18473-Centuri-BullDog-Clone&highlight=centuri+bulldog

    Didn't realize that there are two shrouds for the nose cone simulating a "ram jet" appearance. Interesting.
     
  3. Mar 24, 2018 #3

    rharshberger

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    I recently built one (cloned), not sure if I did a build thread or not, iirc the nosecone was a BNC-70AJ from Balsa Machining with a paper shroud to create the seeker nose cone, it flies great on D12-3s and Aerotech 24mm composites.
    I do have a pdf of the decals I made for it, and a OR file.

    Build thread here: http://tricitiesrocketeers.freeforums.net/thread/357/first-clone-skool-build-pile


    The nose cone tip is actually a cone shroud with a CR520 (BT5 to BT20 centering ring, aka 18mm motor block) as the tip. The original rocket may have been Centuri ST-20 in which case I upscaled it ever so slightly.

    Edit: added photos, unable to add pdf's due to file size, added OR file at bottom



    cen5354CenBull3.jpg cen5354CenBull2.jpg cen5354CenBull1.jpg cen5354CenBull6.jpg cen5354CenBull7.jpg

    View attachment CenturiBulldog.ork
     
    Last edited: Mar 24, 2018
  4. Mar 24, 2018 #4

    GlenP

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    This helps. I think the side view drawing from this post will give me enough info to clone the shape. I am thinking of doing a mini downscale to 13mm engine mount.

    Screen Shot 2018-03-23 at 7.25.20 PM.png

    Thanks very much. That was a really cool design, one of the last few to come from Centuri.
     
  5. Mar 24, 2018 #5

    rharshberger

    rharshberger

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    Actually OpenRocket will print fin patterns, shrouds and centering ring patterns. And if it was some other size like ST20 then the file I included could be scaled to 2.024" to be the actual size.
     
    Last edited: Mar 24, 2018
  6. Mar 24, 2018 #6

    GlenP

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    Cool, yes I have OpenRocket, not a big user, but am learning new things about it. Pretty handy tool. I can print to PDF and import the PDF into Inkscape for scaling. That will be very helpful.
     
  7. Mar 24, 2018 #7

    rharshberger

    rharshberger

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    Actually its easy to just use the scale function and scale the main body tube to the preferred size (it will then scale all parts to correct size) then print a PDF.
     
  8. Mar 24, 2018 #8

    GlenP

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    Cool! See, I am learning new things about OR every day. I am thinking a target scale will be roughly 72%, sort of in the size class of the Estes Curvilinear, but I will make mine very light. Might come close to the diameter of the old Estes RTF Moondog.

    There's also this nice color facecard/catalog picture from 1983: (introduced in 1982 but catalog picture was monochrome)
    http://www.ninfinger.org/rockets/catalogs/centuri83/83cen6.html

    Screen Shot 2018-03-24 at 8.55.56 AM.png

    (P.S. - the Estes Bull Pup came later, introduced in 1986.)
     
  9. Mar 25, 2018 #9

    GlenP

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    I might try this in a few different scales, this is the smallest, at 38%. Outer body diameter is a non-standard 0.84". Here is my initital cardstock template. I have not built it yet, sometimes I discover a few glitches after the first build and tweak things a little. Then I might try a larger 53% scale. I like these small downscales that can fit on one single page.

    View attachment CenturiBulldog.pdf

    CenturiBulldog.jpg
     
  10. Mar 26, 2018 #10

    GlenP

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    this little Puppy is pretty much done. Next to a 1:25.4 scale Nike Smoke cardstock model for comparison.

    DSC_7387.jpg

    DSC_7389.jpg
     
  11. Mar 26, 2018 #11

    rharshberger

    rharshberger

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    Looks great!
     
  12. Mar 26, 2018 #12

    kuririn

    kuririn

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    Nice work! I think I'm gonna try scaling it down to MMX size.
     
  13. Mar 26, 2018 #13

    GlenP

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    Thanks! I forgot to add a part to make the nose cone shoulder and just made that from the scrap. Just make a coupler sized dia, 1" length of tube with a glue tab feather cut to attach the nose part and slide into the body tube part. I guess you could just print this page at 6/13 scale for MMX size engine mount. A few more detailed pictures, I really need my reading glasses to see these up close. The text along the body tube seam matched up pretty well on this one, and now that I think of it I could have shifted the seam to a different quadrant to not fall in the middle of the text - fix later. I just used a simple lap joint. I also notice in the other build threads I am missing the shrouds that go over the launch lugs. I had to color the red portions of the nose cone tip thrust ring with a marker to match the roll pattern. Nose cone shape resembles more of a Bull Terrier (Bulls Eye the Target mascot dog or Spuds Mackenzie from popular advertising some years ago) than a Bull Dog. If you MMX scale it, then I guess you would have a Chihuahua.

    DSC_7390.jpg

    DSC_7391.jpg

    DSC_7392.jpg
     
  14. Mar 29, 2018 #14

    GlenP

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    Here is the 53% scale version. I was planning for this to be a 13mm engine mount, but you could leave that out and use an 18mm instead, with appropriate nose weight for each. I haven't built this one to test it out yet, but wanted to share it here. I would make the fins 5 or 6 ply at the bottom, and maybe 4 or 5 ply at the top. A single-ply cardstock body tube at this diameter will be kind of weak, so it may need another layer or something to strengthen it. You can make some couplers and install them at the parts where it says "CRADLE HERE" where you are most likely to grab it when installing the engine or stuffing the recovery stuff. Also, I shifted the seam to the bottom, if this were hanging by the lugs from under-wing hard point hooks. Usually I put the lugs on the seam, but here the lugs are covered with a fairing strip and made to look like part of the missile's attach points.

    View attachment CenturiBulldog_18_13_53pct.pdf
     
  15. Mar 31, 2018 #15

    GlenP

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    53% next to the 38%.
    DSC_7394.jpg

    Could go with 18mm
    DSC_7395.jpg

    or 13mm
    DSC_7396.jpg

    I made the fins a little thicker for the 53%. I might just permanently install the 13mm mount.
     
  16. Mar 31, 2018 #16

    Brent

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    I have a PDF from Jim Z's site but I think it is to big to upload 3.96 MB
     
  17. Mar 31, 2018 #17

    GlenP

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    Not really a whiz-kid at Open Rocket, but it seems like for the 53% version with an 18mm engine, you have to add more nose weight to get it stable, then the altitude ends up being less than if you keep it light and use a 13mm A10 engine. That is something that I might not have mind-simmed correctly, and might not have gotten a good swing test either. Although, I am not sure if the base-drag stability might not be fully accounted for in the OpenRocket sim either, so the nose weight it wants to put in there might be a little higher than actually needed.

    I think with the small fields I plan to fly at, the 13mm A10 engine will do fine, near 300' apogee, which will be close to out of sight for this little guy.
     
  18. Apr 1, 2018 #18

    GlenP

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    One last update: Little shrouds over the lugs, and a homemade chute that seems to go well with this one.

    8027A145-39D6-4B8A-8B69-4879495E5042.jpg
     
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  19. Jul 25, 2018 #19

    kuririn

    kuririn

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  20. Jul 25, 2018 #20

    GlenP

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    Cool thanks, that actually contains a really good decal scan, will be helpful for anyone cloning that or upscaling it. Thanks for posting the link. Posting the file here, in case that link ever gets broken for future surfers here:

    Interesting that the painting instructions are different than the facecard/catalog picture. I might make another cardstock model to show how the painting instructions look, fins match the color of the body where they attach in this scheme. Also, I did not notice there is a tail band, the catalog picture does not clearly show this.

    . Screen Shot 2018-07-24 at 9.20.05 PM.png
     

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    Last edited: Jul 25, 2018
  21. Jul 25, 2018 #21

    rharshberger

    rharshberger

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    Last edited: Jul 25, 2018
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  22. Jul 25, 2018 #22

    burkefj

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    That's very pretty Rich.
     
  23. Aug 3, 2018 #23

    BABAR

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  24. Aug 3, 2018 #24

    rharshberger

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    Thanks gentlman!
     
  25. Aug 8, 2018 #25

    GlenP

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    Screen Shot 2018-08-07 at 10.56.54 PM.png Here is an alternate version with the paint scheme according to the instructions, not the facecard. Main fins are all white. Two upper fins are red to match the red patch where they are located. The nose cone is rotated so the red parts mate up with the white parts of the body tube. I added the tail band under the aft launch lug. If anyone builds one of these cardstock models, feel free to post a picture here. Not sure if I will get around to building one of these alternate color scheme cardstock models for a while. I have a kit backlog to work on, with a few more in the mail on the way. Screen grab of the new body tube roll pattern, just slightly different, the red block covers the bottom half, when lying on the side and MARINES is right side up.
     

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  26. Aug 9, 2018 at 1:26 AM #26

    GlenP

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    In other news, the AGM-183A will be developed soon by Lockheed Martin. (Bulldog was AGM-83A) But this one may end up looking more like the X-24 Bug, who knows?

    https://www.flightglobal.com/news/a...-claims-both-usaf-hypersonic-programm-450968/
    "USAF awarded a separate deal to Lockheed’s Missiles and Fire Control division in July 2017 to rapidly develop and field the Air-launched Rapid Response Weapon (ARRW, pronounced “Arrow”). The ARRW, now assigned the designation AGM-183A, evolves from the Tactical Boost Glide (TBG) programme launched in 2014 by the Defense Advanced Research Projects Agency (DARPA). By using a rocket to boost the missile to very high altitudes, the unpowered ARRW then glides down to lower altitudes at speeds up to Mach 20."
     

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