noahapiraino
Member
I recently got a Wildman Punisher Super Sport a 2.2" diameter kit with a 38mm motor mount, and was hoping to push it to supersonic for the first time on a J425. However the more I thought about it I started to get worried about potential fin flutter.
The fins are 1/16" fiberglass, so fairly thin. The root chord is 6.5", tip chord 1", and fin span 2.1". My fillets go about 0.25" up the fin span, and I read someone else say that the fillet could potentially be subtracted from the fin span since they'll increase fin stiffness/thickness at the root. There is also a shallow slope on the aft edge of the tip chord, and I was wondering if I could consider that part of the tip chord as well for the sake of the math sheets, increasing it's length to anywhere from 1.5-2".
I've plugged everything in to some fin flutter spreadsheets with a shear modulus of 850,000 psi which seemed to be a good estimate based on a couple other threads as well as a research paper I found. The sheets have been giving me a flutter boundary velocity of ~1200ft/s, but my OpenRocket simmed velocity is ~1350ft/s.
Does anyone have any experience flying supersonic on this kit or with fins this thin?
The fins are 1/16" fiberglass, so fairly thin. The root chord is 6.5", tip chord 1", and fin span 2.1". My fillets go about 0.25" up the fin span, and I read someone else say that the fillet could potentially be subtracted from the fin span since they'll increase fin stiffness/thickness at the root. There is also a shallow slope on the aft edge of the tip chord, and I was wondering if I could consider that part of the tip chord as well for the sake of the math sheets, increasing it's length to anywhere from 1.5-2".
I've plugged everything in to some fin flutter spreadsheets with a shear modulus of 850,000 psi which seemed to be a good estimate based on a couple other threads as well as a research paper I found. The sheets have been giving me a flutter boundary velocity of ~1200ft/s, but my OpenRocket simmed velocity is ~1350ft/s.
Does anyone have any experience flying supersonic on this kit or with fins this thin?
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