Finsim Alternatives

Discussion in 'Rocketry Electronics and Software' started by phyzzld, Feb 11, 2019.

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  1. Feb 11, 2019 #1

    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 #2

    anbhtblr

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    I've had the same contact problem for over a year.
     
  3. Feb 14, 2019 #3

    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 #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 #5

    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 #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
     

    Attached Files:

  7. Feb 15, 2019 #7

    phyzzld

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    This looks great. Thank you.
     
  8. Feb 15, 2019 #8

    mpitfield

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

    phyzzld

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    Thanks David.
     
  11. Feb 15, 2019 #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 #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 #13

    mpitfield

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    Sure do you have a copy?
     
  14. Feb 16, 2019 #14

    phyzzld

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    I agree. It seems weird. The aerorocket website is still being updated as of last month. Why keep up a website for software you allow no one to access?
     
  15. Feb 16, 2019 #15

    rocketguy101

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    He states on the pages...you have to be a US Citizen to obtain the software. ITAR is pretty serious stuff and penalties are high if you violate the law. We have to take classes at work (called Export Compliance) and only certain folks in the organization can be certified to ship drawings, documents, and software to our own employees in some foreign nations. Now why he won't answer emails is another mystery.
     
  16. Feb 16, 2019 #16

    AndrewW

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    I am not sure if it made a difference but a few years ago I made a request for Finsim and never heard back him as well. But prior to my L3 I decided to give it a try again but this time I was very descriptive of the reason I wanted the software and the project I was working on. I got the impression from his response that he doesn’t just give it out to anyone that asks and that simple one line requests may get ignored. Again just a feeling I got not a statement of fact.
     
  17. Feb 16, 2019 #17

    phyzzld

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    I didn't go into great detail about my projects, but it wasn't a one line request either. If people aren't meeting his criteria, he needs to be more specific about what he wants.
     
  18. Feb 16, 2019 #18

    AndrewW

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    Like I said it was just a feeling I got and I might be totally off base.
     
  19. Feb 16, 2019 #19

    dhbarr

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    When someone wants a copy of what someone else has made, the person being asked has no obligation to the person doing the asking.
     
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  20. Feb 16, 2019 #20

    phyzzld

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    This is true. But he advertises it. He invites us to try and gain access to it. Then doesn't follow through with it (ie. accept or deny). It wastes our time. It's our fault if we keep trying. Personally I am not. That is the reason for this thread.
     
  21. Feb 17, 2019 #21

    anbhtblr

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    +1
     
  22. Mar 8, 2019 #22

    aerocfd

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    Interesting, so you say FinSim is not available anymore. Then why have I been sending download links for FinSim by the dozens. However, if a request for FinSim is denied then the reason is the requester did not indicate he or she is a resident of the USA. In addition, it is a violation of copyright to acquire FinSim without my permission. Finally, FinSim has a good database of materials so the comment that FinSim does not have a database of materials is false. However, FinSim has provisions to specify material properties not included in the database. In summary, absolutely everyone who requests FinSim is provided a download link for the program and the flutter and supplemental spreadsheets if their address is in the USA.
     
    Last edited: Mar 8, 2019
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  23. Mar 8, 2019 #23

    aerocfd

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    Anyone following the advice of CoyoteNumber2 is violating my FinSim copyright. Violating copyright is against the law everywhere in the world except maybe China.
     
    Last edited: Mar 8, 2019
  24. Mar 8, 2019 #24

    aerocfd

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    David Stribling, I remember you. You took part in another FinSim bashing post several years ago.
     
    Last edited: Mar 8, 2019
  25. Mar 8, 2019 #25

    phyzzld

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    No offense sir, but how am I suppose to know that. This is the first contact I have ever received from you. However, I am glad to hear this. Also, I did say " at least not to me".

    Are you saying my requests have been denied? This is the first indication my requests have even been received/seen, let alone denied. My last request sent in Jan, 2019 explicitly states that I'm a US citizen and gives my home address in the US.

    This thread was started because I have a problem for which FinSim was the only tool I was aware of for solving it. That tool was unavailable to me, so I did what any good engineer would do and went looking for alternative tools. This is not a FinSim bashing thread. If it has devolved into one that is my fault and I apologize. Frustrations can get the best of us. Take it as a compliment about your software.
     
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  26. Mar 8, 2019 #26

    aerocfd

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    Your request was not denied because I do not remember denying anyone a link to FinSim in the time frame you mentioned. There must have been some reason like maybe your subject line put your request in the Junk folder. However, I do not respond to people who get "frustrated" and use social media to bully me and then use an avatar to hide your identity. Not cool. However, please resend your request and I will immediately send you a link for FinSim like you wanted in the first place but without all the drama.
     
  27. Mar 8, 2019 #27

    aerocfd

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    Jeff, I just sent you a link to download FinSim.
     
  28. Mar 8, 2019 #28

    phyzzld

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    I received the download link. Thank you.

    I previously stated why the thread was started (no bashing or bullying intended), again I apologize for my frustrations. I certainly didn't mean to turn this into a big mess

    No need to hide!

    Jeff Gebhardt
    QCRS
     
  29. Mar 8, 2019 #29

    aerocfd

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    Jeff, when you called your post, "FinSim Alternatives" you made the decision to be controversial and to embarrass me instead of simply asking me by email or on this forum any question you needed answered. I accepted your apology and provided you the FinSim link.
     
  30. Mar 8, 2019 #30

    CoyoteNumber2

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