Fin Flutter

[Dipstick]

Hi all, I'm working on my CAR Level 4 rocket, and have been trying to wrap my head around fin flutter.

Someone passed on a really nice Excel spreadsheet that does calculations to find a velocity where flutter will likely take place (file is just too big to attach). One of the categories that needs to be filled is shear modulus of the fin material. Anyone know where to find that sort of info?

I'm using 3/16 G10 to start with, but adding kevlar and fiberglass laminate layers...


Thanks for any help!

 

[Fdog]

The best results I've found were from a spreadsheet authored by David Harris. You can find it in post #6 in this thread:

https://www.rocketryforum.com/showthread.php?29544-Fin-Flutter-Occurs-at-Higher-Speed-With-Increased-Span-Length&p=265398#post265398

My laborious hand calculations have matched David's results to a few fps, so I have good confidence in his work.

In David's spreadsheet, the shear modulus is listed on the only page in the spreadsheet - just look to the right. OTOH, if you're using the 138-finflutter excel spreadsheet from InfoCentral, you will find shear modulus at the bottom of the page in the Materials tab.


All the best, James

 

[Dipstick]

Thanks James, my results with this were in line with what I expected.

One question, do you know what FR4 is in the shear modulus. It lists: FR4 (same as G10), and G10 (Same as FR4), but gives different values...?