Tell me about the fins. Flutter is readily cured by building up the fins with different resonant frequencies and a taper from base of span to tip. My original SSS bird on an H180 sim'd to just Mach 2 and didn't shred or even come close.

Warren

My fins are pretty big, if you look on public missiles they are the design FIN-A-05. I do not have a taper ont he fins and the rocket is 6 feet tall. So if it wiggles just a bit my rocket will also shred.

I've got a great spreadsheet (from somewhere?) that deals with fin flutter, etc. I'll send it to you both. Elviss_boy, don't have your e-mail, sent it to Warren. He should send it on to you, if it's good. Your A-05's (or Miranda) fins are in there.

Actually kyle you know someone that has gone that fast and the rocket to boot. Give you 3 guesses. And did it on a 54-2550 full K motor.. More then 1 time with the same rocket. Roughly the size your talking of rocket.. but there is some tricks..

Oh, man, Conway! Tell us! 🙂 You know, on the Oktoberfest '05 DVD (from Dave Hanson... plug, plug) you can hear, at least I believe it to be true, a high power rocket with fin flutter. Don't remember which one, but it's obvious. There's kind of a silence, except for that sound. No shred, just a loud vibration sound. Has to be fin flutter. Or not... anyone who has the DVD go through it and LISTEN to the flights... somewhere in the middle, I think...

Thanks Bruce for the spread sheet put im sorry to say i do not understand it at all : /

Well, the noise you speak of bruce is actually a Hybrid flight in the DVD. Know what sound and rocket you mean. hybrids of specific makes if not all make this real fluttery sound as they fly. Thats part of the hybrid sound. At least the only one i found with any noise that had a disinctive sound like you speak.

but MANY MANY moons ago..LOL at the first MHM. I flew 2 K motors in an attempt for the Club K record. (and got it on both flights... First one I stole rec from Wilke then he beat me then I beat him back only the next month to have him beat it again.LOL) My first attempt was with the K700 AT motor. Flew right at Mach 2. Then the 2nd motor was the AMW 2550 case and big K. Jim Amos had been testing his Data collection system with the Mpac and he flew a simular sized rocket actually 2 lbs heaver then mine as well as talller with slightly more fin area. His real time data recording recorded a flight of mach 2 for him with the same motor. He and I did the math with my bird and calculated that the speed was near the area of 2.2 to 2.5 Mach. In fact I got the rocket back and several spots on the nose and around anywhere there was air drag had the paint pretty well burnt up. Cool stuff. The rocket formerly known as VDP ( Vulgar Display OF Power) is now property of Dave Hanson.. That was a great 3" diameter bird.. As far as flutter goes. Look at the thread of my L3 at TRF sometime and see what my solution has always been for that. The big kicker is fin shape and size belive it or not. A delta or Clipped delta like VDP had was the best as to cut the air without flutter as well as leading and trailing edges are beveled with G10 glas fins laminated in kevlar then CF and then Glass. Fin tip to fin tip via the motor tube, Works great to dampen and cut the air just like ya need it.

Kyle, I had the rocket you mentioned in my hands this week - your dad showed it to me. The work you did was FANTASTIC!!!!!!! and I mean that with all my heart. That said, it is my opinion that the span on your fins was too great, the thickness of your fins (1/16") is insufficient (even with the glassing tip-to-tip)l, and your root chord is too short. I flexed the fins, and I don't think your most excellent rocket will survive mach 2...

Mach 2 is really tough to punch through. Your fins have to have almost no discernible flex. Even with lots of tip-to-tip glass, you don't want to have any play in the fins. Flutter will come into play on your rocket, probably sooner than later. FWIW, I have a K rocket that I'm adding 4# of lead to so it stays well below M2. I'd rather give up a few hundred feet - which is a tough thing for me to admit to - than exceed much over 1400mph, which is less than M2.

Your rocket will do awesome on a lot of loads, and it will take you higher than you have ever gone. This is not the booster to try to go M2 on, though... Just my humble opinion.

Your building skills are exemplary (maybe better than your dad's? 😉 Hey, don't tell him I said that!!!!). Keep up the good work!

Wow John that really nice of you. Never had that much apreciation for on of my birds. Im definitly now going to build a new booster. My fins will have about half or less the span ,half inch to inch more root and better design over all. John with your H record you did at heartsal were you hitting mach 2 ? Also I learned my tricks from my dad and he has learned mine so I would say were even. But now we kinda build with our own desings so everyone is different 😉 . Thanks everyone for the help i look at mach 2 MUCH different now.

Kyle, sorry I didn't respond sooner about the spreadsheet. I'll take another look at it at work tomorrow. Haven't looked at it in quite a while. Listen to JW and Conway, and you'll be good. 🙂

Kyle I would agree whole heartedly with john. Ive been away for 3 years but even then you were doing great things and as with time and experince i can only belive that youve gotten better and better. Wilke is probably one of the most expericed flyers I know. (there are many others that stack well also and so many to list but.. ) Doing Mach speeds is an amazing venture. Ive seen may quality builds from people shred in a heart beat as it passed the mach threasholds. Doing 2 times that can be spectacualr in feat itself. So good luck and give a shout if every you need or have questions..

John with your H record you did at heartsal were you hitting mach 2 ?

Nope... that was quite a blast, but IIRC the sims said something like 1200mph. That said, to my eye that boost looked faster than my J570 minimum diameter attempts, some of which are close to 1500mph.

Incidentally, my last J570 attempt shredded. I had 2 successful boosts J570 blasts under my belt, but I kept making the fins a wee bit smaller and the airframe a bit shorter. Stratagem1 went to 16,973'. Stratagem2 was very similar, with slight mods. She lost a fin about 500' into the boost. Ouchie.

JW

Kyle,

The file focuses on G10 and plywood, not on composites. The guy who setup the spreadsheet was getting to composites (2001), but evidently never got any further. You look for the Flutter Velocity (when the fins begin to flutter), multiply that by 2.2 to get your Shred Velocity (when the fins self-destruct). I noticed that the formula for your fin is corrupted. But the best any file can give you is a guess and a mark in the sand. What JW, Warren, and Conway can give you is experience and solid advice. All fins will have a resonance that will go out of control at some velocity. What Warren, Conway and JW do is dampen that resonance so they can increase the velocity their fins will take.

Thank you alot guys. I know now alot more 😀