2 fins and a nose cone...and it flies.

Discussion in 'Low Power Rocketry (LPR)' started by sl98, Feb 10, 2020.

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  1. Feb 10, 2020 #1

    sl98

    sl98

    sl98

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    The recent Apogee Peak of Flight contained a free plan for a 2 fin spin stabilized rocket. The rocket is designed by Kevin Cronwell and is in issue 514. The rocket only requires 6 parts, which I had on hand. The longest part of the build was waiting for glue to dry. Total build time was about 1 hour. I was a little skeptical whether it would fly. I launched today on an A8-3 and it flew straight and true. I don't think I would use a larger motor because you may never find it again. This little guy earned its paint.

    Cygnus - on pad.jpg Cygnus - lift off 1.jpg Cygnus - lift off 2.jpg Cygnus - lift off 3.jpg Cygnus - lift off 4.jpg
     
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  2. Feb 10, 2020 #2

    mbeels

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    Neat! That's a fun idea.
     
  3. Feb 10, 2020 #3

    kuririn

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    Cool!
    First thought: wonder if it can be upscaled?:D
     
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  4. Feb 10, 2020 #4

    gna

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    Nice! I saw that design, too, and thought about building one. I have everything but a coupling laying around here.
     
  5. Feb 10, 2020 #5

    sl98

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    If you have a shorter coupler, you could use a thrust ring and glue the shorter coupler above the thrust ring. You could also try one of the yellow tubes Estes provides for placing thrust rings as your coupler. It might be a little bit of a loose fit but a wrap of tissue paper and soaking in thin CA might make a good fit.
     
  6. Feb 10, 2020 #6
  7. Feb 12, 2020 #7

    gna

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    Just curious--they list 1/8 balsa. Did you use 1/8 or 3/32 balsa?
    I'll have to dig through the bin with all my parts and see what's in there. I looked the other day for BT20 and didn't see any couplings, but I wasn't really looking for them.
     
  8. Feb 12, 2020 #8

    sl98

    sl98

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    I did use 1/8 but it sure is overkill. I think 3/32 would be just fine. I would even try 1/16 basswood if I made another one.
     
  9. Feb 12, 2020 #9

    SDramstad

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    Hmmmmmmmm..........:rolleyes::rolleyes::rolleyes::rolleyes:
     
  10. Feb 12, 2020 #10

    Alan15578

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    Certainly.

    I had an old NACA report that explained it all, but I lost it. I think it dated back to the WWW I era. They wanted to stabilize dropped bombs with planar fins (two fins canted) because they could be packed and dropped more efficiently. NACA figured out how to size and cant the fins, but then fond that such stabilization was unsuitable because the bombs had a larger dispersion pattern. This type of stabilization was most often seen on the Parks water rockets. For sport rockets, it is just a novelty, but I still want to find the report number and the report itself. I think all the old NACA reports are available on line, but there are too many to search through.
     
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  11. Feb 17, 2020 #11

    sl98

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    Painted after maiden flight and made one fin black to make it easier to visualize the spin. You can see almost 1 full rotation in first two pictures as it is leaving the launch rod. Another perfect flight with an A8-3. Time to upscale.


    Cygnus painted (0).jpg Cygnus painted (1).jpg Cygnus painted (2).jpg Cygnus painted (3).jpg Cygnus painted (4).jpg Cygnus painted (5).jpg Cygnus painted (6).jpg
     
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  12. Feb 20, 2020 #12

    sl98

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    Started a 223% upscale using BT-60. Fins are cut. Working on 24mm motor mount. Initially I was thinking rear deploy. I am going to try MM that ejects with a streamer and still breaks rocket in 2 for tumble recovery. If that doesn’t work a switch to rear deploy should be easy.
    0C5AFA9A-60C1-4282-B43B-21D552FD3DE0.jpeg
     
  13. Feb 21, 2020 #13

    gna

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    Here’s mine:
    37B2FBCD-576B-4C71-BFFC-0BC7BB9A12FE.jpeg I papered the fins for a bit more strength. Of course, there’s no green grass here, so it’ll be a while before it flies, or gets painted...
     
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  14. Feb 23, 2020 #14

    sl98

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    Ready to begin final assembly of "Big Cyg." Not pictured is 18" upper tube, PNC-60AH nose cone, kevlar, and steamer that will be attached to motor mount. The coupler serves as a thrust ring for the the motor mount. The nose block will be glued in about 1 1/2 inches from the bottom of the upper tube. First flight will be on a C11-3. The new C5-3 might be a good option too.

    There is a lot of flexibility with this design. If it flies well, I could make another motor mount for 29mm. ;) The set up will also make it easy to convert to rear deploy if the eject/tumble separation doesn't work or if it becomes too difficult to track MMT and rocket coming down separately.

    Big Cyg Parts.jpg
     
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  15. Feb 23, 2020 #15

    sl98

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    Big Cyg is ready for primer and a first flight.

    Big Cyg.jpg
     
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  16. Mar 1, 2020 #16

    sl98

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    I took Big Cyg out for its first flight today along with original Cygnus. Big Cyg was loaded with a C11-3 and Cygnus was loaded with a B4-4. Big Cyg's flight was dramatic and cut short by a CATO.

    I got some of the best CATO pictures I've ever taken. The flame coming out of the rocket looked larger that a H128. The motor mount was destroyed and the upper tube will have to be replaced. The fin can is fine. The repairs shouldn't take take that long.

    No pics of Cygnus on a B4-4 because I wanted to focus my attention on tracking it. Cygnus shot off the pad laser straight. Nice deployment and tumble down.

    I've noticed Cygnus likes to come in nose first. Fortunately the grass is still soft. For Big Cyg, I actually designed it to hopefully shake the nose cone free and tumble down in 3 pieces. After repairs, I will test this concept on Big Cyg.

    Big Cyg & Cygnus.jpg Big Cyg.jpg Big Cyg Liftoff 1.jpg Big Cyg Liftoff 2.jpg Big Cyg Liftoff 2A.jpg Big Cyg Liftoff 3.jpg Big Cyg Damage.jpg
     
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  17. Mar 2, 2020 #17

    BABAR

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    Wow!

    There’s one to put in the Lift Off Gallery.

    Or maybe start a Best CATO Gallery
     
  18. Mar 2, 2020 #18

    ebruce1361

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    Has anyone ever built a one-fin rocket? I'm thinking of a spiral that wraps around the body so it behaves like a ring fin, but is one piece.
     
  19. Mar 2, 2020 #19

    lakeroadster

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    Like a Dr. Evil's subterrenian drill... but it goes up, instead of down....
     
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  20. Mar 2, 2020 #20

    ebruce1361

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    Kinda like that! I was thinking a bit longer though. WIN_20200302_12_32_50_Pro.jpg
     
  21. Mar 2, 2020 #21

    dhbarr

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  22. Mar 21, 2020 #22

    sl98

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    I took advantage of nice weather and an empty field to try Big Cyg again. This time, I used a D12-5. Lift off was straight and true for the first 20-30 feet (Pics 1-5). Then Big Cyg started to corkscrew (Pics 6-8). Ejection worked as planned. The rocket separated into two pieces to tumble down and the motor mount spit out and came down on 2 - 6 foot long streamers (actually 12 feet of streamer tied in the middle to the mount) (pics 9-10).

    Apogee: 684 ft.
    Max speed: 255.2 ft/s.
    Time to Apogee: 7.68 sec

    Original Cygnus had two flights on a A8-3 and B4-4. Perfect flights but no pictures.

    Big Cyg 1.jpg Big Cyg 2.jpg Big Cyg 3.jpg Big Cyg 4.jpg Big Cyg 5.jpg Big Cyg 6.jpg Big Cyg 7.jpg Big Cyg 8.jpg Big Cyg 9.jpg Big Cyg 10.jpg
     
    Last edited: Mar 22, 2020
  23. Mar 22, 2020 #23

    BABAR

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    Nothing wrong with corkscrewing as long as net trajectory remains relatively vertical!
    Makes for a neat smoke trail, and keeps altitude manageable for smaller fields and shorter walks.
     

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