I'm launching my 2.6" fg screech on a L935 to mach 2.9 And hopefully around 19,000 feet.
I think your sim is a bit optimistic on the mach 2.9...probably closer to 2.1 if your .0625" thick fins don't fail.
My bad, I checked the sim again and it says mach 2.38. I built my screech really light, but I have 1" diameter fillets on it. You really think I need to reinforce the fins a bit? Even with those beefy as hell fillets? If so I could do t2t layup on them. I thought the through the wall mounting and internal fillets with rocketpoxy would be strong enough to hold onto the fins.That sounds more likely. Id imagine those fins will need some help.
the sim for my screech says M 1.8 and 18K. Maybe a mistype?
My bad, I checked the sim again and it says mach 2.38. I built my screech really light, but I have 1" diameter fillets on it. You really think I need to reinforce the fins a bit? Even with those beefy as hell fillets? If so I could do t2t layup on them. I thought the through the wall mounting and internal fillets with rocketpoxy would be strong enough to hold onto the fins.
Ok, I will do that, thanks for the advicei dont think the fillets will fail. I would take a close look at finsim and evaluate if the fins themselves will flutter and basically explode.
My bad, I checked the sim again and it says mach 2.38. I built my screech really light, but I have 1" diameter fillets on it. You really think I need to reinforce the fins a bit? Even with those beefy as hell fillets? If so I could do t2t layup on them. I thought the through the wall mounting and internal fillets with rocketpoxy would be strong enough to hold onto the fins.
Fillets are definitely going to help. Don't get me wrong I am not saying with any confidence that I feel that your fins would fail, but of all the components in the design 1/16th G10 fins for Mach 2 flight may be your weak link.
I agree with Dave's recommendation. Check the numbers to gain a bit more confidence on your flight profile and run the fins through FinSim. If the numbers provide a good margin then I would say go with the numbers that is if you're confident you did the analysis correctly. If the numbers are marginal then I would go on the conservative side and do some reinforcing such as a single layer T2T, or whatever you feel is warranted.
Having said that, safety factor aside, what you do should be dependent on your goals. If you just want to push it for a personal best or record attempt then that is when pushing the limits is justified, without being reckless. But if you want to confidently enjoy many flights with some abuse on the rocket then that is when some over-building is well justified. The controversial and subjective thing is what constitutes over-building.
There is another reason to "over-build" and that is something that I practice. I like to use new building techniques in order to gain some hands on experience on designs that don't require it, this way I am better experienced for builds that do require it.
All the university attempts at 20,000 ft multistages died horridly last year in L-1 motors. Stick to 19.5 k ft and don't over stress the airframe or electronics. If you want to be optimistic try to beat the current TRA record. Honestly that's hard enough and still realistic.That make a lot of sense. I just emailed to get a copy of finsim with my school email, so hopefully that's enough proof to get it. I couldn't find a way to pay for it, which I wouldn't mind paying something for it, but all well. I'll just wait for the response. I like to overbuild my rockets too, but I really want to push the envelope with this rocket. I'm trying for 20,000 feet, and my sim is putting it 500 feet short of what I'm going for, but I also don't want to loose my investment in this rocket, as I really do like it.
Thanks,
Matthew
Honestly I'm surprised they held up to break 1000 mph.
i don’t think the fillets will fail. I would take a close look at finsim and evaluate if the fins themselves will flutter and basically explode.
Decided to push the envelope, launched an H90 in my dual deploy star orbiter, watched it rip apart in the sky. Once I found the ebay the strattologger beeped out 1904 feet with a top speed of 1064mph it was pretty insane. This was all that was left. Totally worth it.
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