I am trying to better understand fin flutter, and how to know when a chosen fin material, and thickness, is sufficient for a given project without overbuilding.
The specific project is a 4" diameter rocket, about 75" long, weighing about 29lbs with the motor. The maximum velocity expected is mach 2.2, and a projected altitude of 33k' ish, possibly higher with some adjustments. The current fin design that I am looking at has a root chord of 11", a height of 3.75", a sweep length of 10.5", a tip chord of 1.5", and a sweep angle of just over 70 degrees. There will be a simple bevel on the edges, of 7-10 degrees. There are 4 fins. The stability is sitting at 1.58 cal. This is a through the wall construction, with a 75mm motor mount. This is not a tip to tip cloth reinforced design. There will be internal and external fillets.
The material I have been thinking of is 3/16" G11, and I am basing this on what I can gleam from other peoples successful projects and what is sold with kits.
In the OR sims, the difference between the 3/16" G11 fins, and some .125" pre-preg 0-90 uni Dragonplate CF, is around 1000' and slightly improved stability.
I have looked for a fin flutter calculator, but the one I found looks to be unavailable to common folk. I would rather have the actual numbers to back up the 'how much is enough', rather than just trying to 'guess on the safe side'.
With the above fin profile, is it likely that the CF plate I mentioned would be stiff enough?
If it is easy for someone to run a fin flutter analysis, or point me in a direction to where I can do this myself, that is the info I would prefer.
Thank you all, in advance.
The specific project is a 4" diameter rocket, about 75" long, weighing about 29lbs with the motor. The maximum velocity expected is mach 2.2, and a projected altitude of 33k' ish, possibly higher with some adjustments. The current fin design that I am looking at has a root chord of 11", a height of 3.75", a sweep length of 10.5", a tip chord of 1.5", and a sweep angle of just over 70 degrees. There will be a simple bevel on the edges, of 7-10 degrees. There are 4 fins. The stability is sitting at 1.58 cal. This is a through the wall construction, with a 75mm motor mount. This is not a tip to tip cloth reinforced design. There will be internal and external fillets.
The material I have been thinking of is 3/16" G11, and I am basing this on what I can gleam from other peoples successful projects and what is sold with kits.
In the OR sims, the difference between the 3/16" G11 fins, and some .125" pre-preg 0-90 uni Dragonplate CF, is around 1000' and slightly improved stability.
I have looked for a fin flutter calculator, but the one I found looks to be unavailable to common folk. I would rather have the actual numbers to back up the 'how much is enough', rather than just trying to 'guess on the safe side'.
With the above fin profile, is it likely that the CF plate I mentioned would be stiff enough?
If it is easy for someone to run a fin flutter analysis, or point me in a direction to where I can do this myself, that is the info I would prefer.
Thank you all, in advance.