ISO Fin Flutter Analysis Spreadsheet/Progam

[School of Rock'et']

All,
I believe aero fin sim is no longer available to the public. There may be a fin flutter analysis spreadsheet that allows a user to input the exact dimensions and # of fins to generate approximate fps velocity point of potential failure. Can someone share this spreadsheet or point me in the proper direction?

Much appreciated!

 

[Banzai88]

Search here for the recent thread, it's been made available again.

ETA: I've been searching for the thread. It was one of mine that I started. Looks like it got nuked for some reason, but the owner is a poster here and he posted the download link and password.

I would suggest that you send the web owner an email, likely you'll get a positive response.....unless he's changed his mind...again.

 

[UhClem]

Here is what I found floating on my hard drive...

 

[Blast it Tom!]

Ah, much thanks @UhClem. I have quite a vibration/natural frequency analysis background, but as I noted in the file, he runs into the same issue - material properties. Composites (layered materials), wood, etc. can be right devils to get any reasonable property values for; they are directional, non-isotropic, all that nasty stuff that makes even a finite element analysis a question mark. Throw in soaking balsa in CA or papering fins, birch plywood, etc. and Houston, we have a problem (most overused line on the forum, likely...) There may be a way around it by test, but even that takes special equipment, and while I do have access to some of it, I need to consider how I'd do it. We're supposed to be getting a non-contact (laser) pickup, and that could be really useful. Twang a sample piece of material, get the cantilever frequency, back in some material properties, and a lot of progress could be made. But then you get into that NACA paper, which I haven't looked at yet. Fluid mechanics correlations can be ... interesting!

I noticed a database of cases in the sheet where fins shredded, survived, etc. Very interesting! Of course it is possible to get through a resonance depending on the damping and how fast you can accelerate through it, etc. as is done with rotating machinery a lot.

ETA: @Banzai88, is the onwer you mentioned the fellow listed here? - https://www.aerorocket.com/finsim.html
The name sure seems familiar and it sure looks like he's done a better job than me starting from that spreadsheet and the NACA paper.

ETA AGAIN: Holy Smokes, John has a resume that is over-the-top for this application! So the OP is noting that John has stopped distribution in the US, then. I'm kinda slow on the uptake; please forgive me.

 

[UhClem]

Another complication is that one of the assumptions in the NACA paper is that the fins have a constant t/c ratio. In other words the thickness is tapered from root to tip. Not a very common sight around here. It has been a while since I looked at it but I could never quite decide if a flat plate is better or worse.

As for material properties, putting your high dollar stiff material on the surface is best. A balsa core with carbon fiber skin gets you most of the benefits of solid carbon fiber but with a far lower cost.

John's resume lacks something. He lists universities but fails to mention degrees earned.

 

[Blast it Tom!]

Another complication is that one of the assumptions in the NACA paper is that the fins have a constant t/c ratio. In other words the thickness is tapered from root to tip. Not a very common sight around here. It has been a while since I looked at it but I could never quite decide if a flat plate is better or worse.

As for material properties, putting your high dollar stiff material on the surface is best. A balsa core with carbon fiber skin gets you most of the benefits of solid carbon fiber but with a far lower cost.

John's resume lacks something. He lists universities but fails to mention degrees earned.

Interesting, the lack of degrees part; perhaps is just not important to him. But what he's got going there is certainly impressive. I grabbed the NACA paper just for future reference; thanks for the heads-up. And the fin construction tip as well; makes sense.

From my first thoughts, I would think tapered is better - bending moments are maximum at the fin base, so for the same material quantity, a tapered fin will be stronger and have a higher cantilever natural frequency, to be sure. But aeroelastics is a bit out of my area - I wonder, for instance, if you could just get tip flutter, or the fluttering of some portion of the length as it tapers out to a thin section. Hmm.

 

[Johnly]

Here's the Excel based spreadsheet I have:

 

[rfjustin]

https://www.rocketryforum.com/threa...insim-recently-2015-2016.137122/#post-2065926

 

[heada]

https://www.rocketryforum.com/threa...insim-recently-2015-2016.137122/#post-2065926

The link in your link goes nowhere. It has been removed. The software is no longer available for download.

 

[rfjustin]

The link in your link goes nowhere. It has been removed. The software is no longer available for download.

Bummer, that's new since the last time I viewed said thread.

 

[Banzai88]

There was a thread that I started here, about a month ago, where I asked about the current restriction.
https://www.rocketryforum.com/threa...ble-to-the-usa-any-replacement-for-it.162735/

After overwhelming response, John Cipolla, TRF username aerocfd, responded by posting the username and password for us to download.

That thread has since been completely wiped from TRF, along with any other thread where the link was posted. Shame, I would have thought that selective editing would have been the way to go.

 

[aerorocket]

John's resume lacks something. He lists universities but fails to mention degrees earned.

Here is my response to this trolling comment. My real resume is none of your business and will never be listed online. I have a BSME and an MSME in mechanical and aerospace engineering where I made deans list 3 years in a row.

Thanks.
John Cipolla

 

[aerorocket]

There was a thread that I started here, about a month ago, where I asked about the current restriction.
https://www.rocketryforum.com/threa...ble-to-the-usa-any-replacement-for-it.162735/

After overwhelming response, John Cipolla, TRF username aerocfd, responded by posting the username and password for us to download.

That thread has since been completely wiped from TRF, along with any other thread where the link was posted. Shame, I would have thought that selective editing would have been the way to go.

My response here is that I did not delete anything from the thread you talked about. The thread was probably deleted by the Rocketry Forum because the comments by a few of the trolls were personal attacks, unprofessional and provocative. The free FinSim download link was added very early in the conversation after one TRF member (not you) suggested asking John politely for a download link and I responded "That will work" and that's all I said in the entire thread.

Thanks.
John Cipolla

 

[aerorocket]

Search here for the recent thread, it's been made available again.

ETA: I've been searching for the thread. It was one of mine that I started. Looks like it got nuked for some reason, but the owner is a poster here and he posted the download link and password.

I would suggest that you send the web owner an email, likely you'll get a positive response.....unless he's changed his mind...again.

Your last comment was not necessary as was the provocative title of your original thread.

Thanks.
John Cipolla

 

[UhClem]

Here is my response to this trolling comment. My real resume is none of your business and will never be listed online. I have a BSME and an MSME in mechanical and aerospace engineering where I made deans list 3 years in a row.

You made it everyone's business by putting it on your web pages but for some reason leaving off degree's earned. Which I always thought was the most important thing. Or at least it was to me.

 

[aerorocket]

You made it everyone's business by putting it on your web pages but for some reason leaving off degree's earned. Which I always thought was the most important thing. Or at least it was to me.

It's none of your business to see my resume. You are a troll.

 

[UhClem]

It's none of your business to see my resume. You are a troll.

When did I ask to see your resume?

 

[Banzai88]

It's none of your business to see my resume. You are a troll.

You're the only one trolling here. You're in the public sphere. Grow up or move on.

 

[Banzai88]

Your last comment was not necessary as was the provocative title of your original thread.

Thanks.
John Cipolla

Not really sure how "Finsim no longer available to the usa. Any replacement for it" is provocative? IDK who deleted it, I can only imagine it's because it reflected poorly on you, thus was easier to blow out than to edit, as mods have repeatedly said they do often to make things easier on themselves.

Point of fact, YOU HAVE changed your mind at least twice on allowing it.....

God forbid someone be pointed to YOU, the gatekeeper of the software in question, as would only be proper! You have a real persecution complex.

 

[JoePfeiffer]

Here is my response to this trolling comment. My real resume is none of your business and will never be listed online. I have a BSME and an MSME in mechanical and aerospace engineering where I made deans list 3 years in a row.

You don't have to provide a resume. When you do, you're telling people what your credentials are, and they use that as a rough guide to how much credibility you have. For you to post a false resume is to intentionally mislead people.

 

[JoePfeiffer]

While we're posting software, here's a couple of little Python scripts I wrote based on the formulas in Apogee's Peak of Flight #291. I hereby place this code in the public domain for anyone to use for any purpose whatever. I've changed the extension from .py to .txt to get through TRF's filename filter.

Of course, if anyone finds any bugs please let me know!

 

[Buckeye]

While we're posting software, here's a couple of little Python scripts I wrote based on the formulas in Apogee's Peak of Flight #291. I hereby place this code in the public domain for anyone to use for any purpose whatever. I've changed the extension from .py to .txt to get through TRF's filename filter.

Of course, if anyone finds any bugs please let me know!

Nice. There is plenty of info out there, and any engineering student can work up the equations. I'm sure Jon Coker would host the tools on his site, too. No need to treat FinSim like the holy grail and put up with the author's antics.

-Buckeye (official enemy #87 on the aeroCFD black list)

 

[icyclops]

Wow, people calling others trolls and fighting over posting degrees....who the hell cares.
This is suppose to be a fun and knowledgeable place for this hobby.

Please be kind to one another...better things happen because of it.

 

[mikec]

While we're posting software, here's a couple of little Python scripts I wrote based on the formulas in Apogee's Peak of Flight #291.

Thanks! Of course, I've always been skeptical that these equations could realistically capture the material properties of the typical hobby fin layup with a substrate, fiberglass or CF tip-to-tip, surface mounted fins or slots, etc. The original NACA report was talking about metal fins and bolted, very rigid, joints and just uses a single isotropic shear modulus (which is noted, but somewhat glossed over, in the PoF article.)

 

[JoePfeiffer]

Thanks! Of course, I've always been skeptical that these equations could realistically capture the material properties of the typical hobby fin layup with a substrate, fiberglass or CF tip-to-tip, surface mounted fins or slots, etc. The original NACA report was talking about metal fins and bolted, very rigid, joints and just uses a single isotropic shear modulus (which is noted, but somewhat glossed over, in the PoF article.)

My guess is our practices (through the wall with internal fillets, tip-to-tip glassing....) are plenty stiff enough for the equations to be applicable. Trying to find believable figures for shear modulus is the hardest problem I've faced -- and the fact that it's non-isotropic doesn't concern me, as long as I can know the worst case.

 

[shockie]

what happens when you put a bunch of know-it-all old white men in a room together: they argue about nothing.... or something. Or everything.

“Never argue with a fool, onlookers may not be able to tell the difference.”

 

[JP Johnston]

https://www.rocketryforum.com/threa...insim-recently-2015-2016.137122/#post-2065926

I have a copy of the latest AeroFinSim.

 

[jbrracer]

I have a copy of the latest AeroFinSim.

any chance you can run something for me? Id be so greatful

 

[JP Johnston]

any chance you can run something for me? Id be so greatful

Sure can...

 

[JoePfeiffer]

I decided to spend a couple of hours combining my python scripts above and improving their interface. The attached script continually recalculates the fin thickness or flutter speed as you modify the parameters; modifying anything except flutter speed recalculates flutter speed; changing flutter speed recalculates fin thickness. Unfortunately, TRC won't let me upload a ".py" file, so I'm uploading it as a .txt.