Finsim Alternatives

Discussion in 'Rocketry Electronics and Software' started by phyzzld, Feb 11, 2019 at 4:26 PM.

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  1. Feb 11, 2019 at 4:26 PM #1

    phyzzld

    phyzzld

    phyzzld

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    I'm currently working on a 54mm md design. I'm playing with different fin shapes and sizes. The sims have the max velocity as high as mach 3.1. With these speeds, I would like to look at fin flutter as well.

    I've tried to contact John Cipolla of Aerorocket (including here on TRF) for the past couple of months to get access to finsim but he has not responded. I assume this means finsim is not available (at least not to me anyway). I wanted to find out how others are doing fin flutter analysis for their rockets and what alternatives to finsim exist.

    Thanks,
    Jeff
     
  2. Feb 14, 2019 at 1:45 AM #2

    anbhtblr

    anbhtblr

    anbhtblr

    Rich@bna TRF Supporter

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    I've had the same contact problem for over a year.
     
  3. Feb 14, 2019 at 7:47 PM #3

    phyzzld

    phyzzld

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    Wow. That's too bad. I haven't seen anybody on TRF talking about getting finsim for quite some time.
     
  4. Feb 15, 2019 at 12:02 AM #4

    rocketguy101

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    Are you looking for a software program only, or are you asking how to calculate fin flutter in general? There are some spreadsheets floating around that will estimate the maximum velocity for a fin, and Apogee's Peak of Flight #291 has an article about the subject. The spreadsheets are posted somewhere on this forum, search on the topic. FinSim models on a simplified fin, like the spreadsheets do. It does have a built-in material database so you don't have to look up the properties, but you can find them on the web like at MatWeb.
     
  5. Feb 15, 2019 at 7:42 PM #5

    phyzzld

    phyzzld

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    I was mainly thinking of software when I started the thread, but I'll gladly take any help I can get. I've been reading everything I can to learn about fin flutter and hopefully know enough to do a rough estimate of the flutter velocity. I was hoping to use finsim as another source for comparison, but without access to it, I wanted to see if there were any other tools I could use.
     
  6. Feb 15, 2019 at 8:11 PM #6

    clreynolds

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    Here is a spreadsheet I put together many moons ago from Apogee's Peak of Flight news letter. Only fill in the light yellow boxes, everything else is calculated.

    The hardest part is determining a materials shear modulus. You also need to use RockSim or OpenRocket to determine the altitude at max speed.

    Good luck
     

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  7. Feb 15, 2019 at 8:17 PM #7

    phyzzld

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    This looks great. Thank you.
     
  8. Feb 15, 2019 at 8:40 PM #8

    mpitfield

    mpitfield

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    +2, two requests over the last few years = zero responses.
     
  9. Feb 15, 2019 at 10:08 PM #9

    rocketguy101

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    search on "fin flutter" came up with many hits...this thread (post #2) has a link to another thread with a spreadsheet that sounds like it matched some results
     
  10. Feb 15, 2019 at 10:49 PM #10

    phyzzld

    phyzzld

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    Thanks David.
     
  11. Feb 15, 2019 at 11:05 PM #11

    UhClem

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    One problem with the methods based on that old NACA paper is that the equations derived assume that the fin has a constant thickness to chord ratio. (Appearing in the equation as (t/c)^3) In other words, if the fin tip is shorter than the root, it is also thinner. It is a rare fin that matches that description.

    Is that good or bad? I don't know but in general thicker fins are stiffer and have higher flutter velocity so I suspect that it tends to make the results conservative. Which would be a good thing given our general fuzziness on material properties.
     
  12. Feb 16, 2019 at 1:43 AM #12

    CoyoteNumber2

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    If you've made a good faith effort to obtain FinSim from the author and he won't respond, then I'd say there's no harm in getting a copy from someone else.
     
  13. Feb 16, 2019 at 1:56 AM #13

    mpitfield

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    Sure do you have a copy?
     

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