Apogee fin shape experiment build

Discussion in 'Low Power Rocketry (LPR)' started by bikefxr, Feb 17, 2019.

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  1. Feb 17, 2019 #1

    bikefxr

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    My sons science fair project taking shape IMG_1550432948.102655.jpg
     
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  2. Feb 22, 2019 #2

    BABAR

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    looking good!
    Lots of balsa to finish!
     
  3. Feb 22, 2019 #3

    neil_w

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    Good stuff. Wouldn’t mind seeing the results when finished if you’re so inclined (after the fair of course)
     
  4. Feb 24, 2019 #4

    bikefxr

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    Sure I’ll post the results
     
  5. Feb 28, 2019 #5

    kkooch

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    If no airfoil on any....the fins with the least surface area will win out (ellipse).
    If a marginally stable model and/or wind and the model has to correct itself....the fins with the largest tip chord will win out.
    Overall, the model will go to a lower aoa (=lower overall drag) with larger fin tip chords to stable.
    Any of those with a good airfoil will win out vs. no air foil!

    A cool project no doubt!

    Kooch
     
  6. Mar 1, 2019 #6

    BABAR

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    Airfoiling vs not definitely a factor

    Also wondering how much "finishing" affects drag
    Rough balsa
    Sanded balsa
    Papered balsa
    Filled balsa
    Nathan-ized balsa.
     
  7. Mar 1, 2019 #7

    Zeus-cat

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    How are you measuring altitude? I recommend sticking to just a few variables and flying them multiple times on the same motor. Motors can be + or - 10% in thrust
     
  8. Mar 2, 2019 #8

    bikefxr

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    We are using a jolly logic altimeter two for speed and altitude and multiple flights
     
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  9. Mar 2, 2019 #9

    bjphoenix

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    I was curious about this too. I was wondering about square-edged fins vs. rounded edges vs. airfoils.
     
  10. Mar 2, 2019 #10

    Zeus-cat

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    Excellent.
     
  11. Mar 16, 2019 #11

    bikefxr

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    Ready for flights tomorrow IMG_1552708506.915499.jpg
     
  12. Mar 17, 2019 #12

    mjennings

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    Awesome that looks like a lot of fun! Don't forget your son can submit his project to NAR and potential get a year free junior membership
     
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  13. Mar 19, 2019 #13

    BABAR

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    Cool!
    With ten different flavors, how many flights are you doing on each to get statistically relevant data?

    I really like #10!
     
  14. Mar 19, 2019 #14

    BABAR

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    Be sure there is a vent hole so altimeter reads right
     
  15. Mar 19, 2019 #15

    bikefxr

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    Was doing 3 fights with each the vent holes were already in the payload bay
     
  16. Mar 19, 2019 #16

    bikefxr

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    #10 went the highest 424 feet fastest went 108mph pulled 9.8 gs at lift off used a Estes C 6-5
     
  17. Mar 19, 2019 #17

    bikefxr

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    I’ll post the rest of data later that’s all I could remember
     
  18. Mar 25, 2019 #18

    58pan

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    I keep refreshing this page hoping you have posted the data.
    Curious if #10 went highest AND fastest or if one of the others went fastest.
    Very interesting test, looks like it was a lot of work.
    Dying to see the results.
     
  19. Mar 25, 2019 #19

    bikefxr

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  20. Mar 25, 2019 #20

    bikefxr

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    Number 10 was the highest 409 feet and Number 4 was the fastest at 106 mph
     
  21. Mar 25, 2019 #21

    bikefxr

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    Took the average of 3 flights
     
  22. Mar 25, 2019 #22

    58pan

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    Interesting! the down swoop (4) was fastest but 63 ft. short of highest. The up swoop (10) was highest and only 1mph short of fastest.
    Were the numbers you averaged pretty close?
    I would have expected 9 to do the best just because it extends the least distance from the body tube but it was just in the middle of the bunch.
     
    Last edited: Mar 25, 2019
  23. Mar 25, 2019 #23

    dhbarr

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    Are all the edges square?
     
  24. Mar 25, 2019 #24

    58pan

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    They look square in the picture.
    Very interesting test and I hope his son wins at the Science Fair but I think this shows there are more variables involved than shape. Numbers 1,6,and 7 are very close to the same shape but 1 was lowest and slowest and 7 was only 8 ft. from the highest and 1 mph from the fastest.
    Best thing about the test.. They got to launch 30 Rockets !!!
     
  25. Mar 25, 2019 #25

    bikefxr

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    We left the edges square so the edges were the same and eliminate the variable of differences in the edge if we rounded them and there were not the same
     
  26. Mar 25, 2019 #26

    bikefxr

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    The number for each launch could vary 20 feet but the speed was always fairly consistent
     
  27. Mar 25, 2019 #27

    neil_w

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    Interesting results. I would like someone to attempt an explanation as to why the crazy shape of #10 did best, while elliptical fins (#1) did worst by a wide margin. Not what I would have guessed, that's for sure!
     
  28. Mar 25, 2019 #28

    BSNW

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    Bikefxr-
    Dude- You are the coolest. I would have loved to do this kind of project when I was a young. Kudos to you! This is very interesting. Wow!
    Andrew
     
  29. Mar 25, 2019 #29

    BSNW

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    Were all the flights done on the same day with the same weather conditions, launch angle etc. Just curious...
    Andrew
     
  30. Mar 25, 2019 #30

    bikefxr

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    Thank you was all my sons idea I just helped... made me a BAR again
     

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