Playin' With Fire 2.0 - "Flight"

[Aksrockets]

Its that wonderful time of year when I crash big rockets. This one's the biggest and crash-iest of them all. Since last year's project went so well gavel Manny and I are building an even bigger one.
The design is pretty simple.
98mm 6g xl flying case. All composite fincan, FWFG Conical NC, Conical coupler that bolts onto the front of the motor case, Raven and SL100 in the AV bay, RF tracking, cable cutter deployment.
The motor will be about an 17,500ns N3500 72/10 propellant, but I think Manny is more qualified to talk specifics about that.
As for performance, I'm expecting velocites in the mid M3 range and 40,000 - 50,000 feet.


Crossing my fingers to have this done by Aeronaut. It might be hard because I also have to juggle college stuff, friends, and working 10-12 hours a day in a metal shop. I only have 2 months to build! :shock:

Alex

 

[conman13]

Subscribed

 

[nute]

op:

Nate

 

[stealth6]

Well, if you actually PLAN on crashing it, that might make the build itself a lot simpler and more efficient - you can cut all kinds of corners, buy cheaper materials, rush through the steps, and generally do a lousy job of it.

But, this way it will be a lot less stressful, won't take time away from important things like college prep, not get in the way of work and such, etc. Also, your mind will be more at ease on launch day itself, as you will have much more confidence in your (intended) result.

Sounds like a plan for success!

(but seriously, I'm jealous and enthused about yet another very cool Aksrockets project - best of luck, mang!)
s6

 

[tfish]

Alex, If you feel this rocket is not flight worthy, please do not bring it to Aeronaut!

Tony Alcocer

 

[crossfire]

I hope it will be fly somewhere with a lot of open places. I don't want to have something go wrong and see another club loose their launch site.

 

[butalane]

Cool project.

Didn't the last FWFG NC end up in like 3 pieces?

 

[Aksrockets]

Well, if you actually PLAN on crashing it, that might make the build itself a lot simpler and more efficient - you can cut all kinds of corners, buy cheaper materials, rush through the steps, and generally do a lousy job of it.

But, this way it will be a lot less stressful, won't take time away from important things like college prep, not get in the way of work and such, etc. Also, your mind will be more at ease on launch day itself, as you will have much more confidence in your (intended) result.

Sounds like a plan for success!

(but seriously, I'm jealous and enthused about yet another very cool Aksrockets project - best of luck, mang!)
s6

Lowered expectations are the key to happiness. S6 I keep forgetting i have all your stuff! You gotta remind me about that man!


Of course I wouldnt fly it if I didnt think it was flight worthy. I wouldnt even build it if I didn't think it would work. The crashyness stuff was just joking about a previous situation.


Alex

 

[mannyskid]

I have the motor end of this project covered. I will be test flying the motor this weekend in a 6" Darkstar. I will post results after the flight.

 

[markkoelsch]

I have the motor end of this project covered. I will be test flying the motor this weekend in a 6" Darkstar. I will post results after the flight.

Can I ask a silly question to the thread as a whole. Why would you build a bigger one if the smaller one did not work? It would make sense to get the smaller one working first so you know your design and techniques are sound before going larger.

 

[prophecy]

Can I ask a silly question to the thread as a whole. Why would you build a bigger one if the smaller one did not work? It would make sense to get the smaller one working first so you know your design and techniques are sound before going larger.

Y'all are too much. The requisite skills to build a 3" min dia are no different than those to build a 4" min dia, and Alex is looking to apply what he learned last year. The reality is that neither project is super challenging.

Just because he's exposed himself to criticism by posting his project on a forum doesn't make it any more or less safe than any other project where the opinions of strangers weren't solicited. The fact that his own self-deprication, which is a refreshing change from all the OpenRocket experts around here, is what led to the criticism is the cruelest irony of all.

Alex - if Mat and I decide to buy stock in Red Bull and I quit my job, we should have our case bonded finocyl done by Aeronaut, but XPRS is looking more likely at this point. Build on and have fun-

 

[Bat-mite]

Wouldn't it get better aerodynamics with a VK NC instead of conical?

 

[stealth6]

For the record, my own post was very much in jest. I'm fairly sure that Alex got that, as did SOME others, but apparently not everyone did.

And yes, I also "got", and appreciated, Alex's own self-deprecating tone, (and yes it is refreshing).

Clear and windless skies to you Alex & Manny, good luck with this build/flight.

Alex, I'll be in contact soon regarding getting "my stuff",
s6

 

[BLKKROW]

I am excited to watch the build. If it happens in time for Aeronaut I will be there to give you hand

 

[Aksrockets]

I cut out the fins with a jigsaw. This is how I do all my carbon fins, so I've gotten pretty good at it if I say so myself. Jigsaws the ultimate fin cutting tool if you're wondering.

Pro tip: cover the CF with masking tape for easier marking.



Bzzzzzz........


Stack sanded w/ a belt sander.


All 4 fins done.

More in the next post.

Alex

 

[Frozenferrari]

I wouldnt really call last year's project a failure though. The motor performed unexpectedly fast and sent the rocket faster than designed to go. Which spun it out. The nosecone became overloaded and snapped, hitting a fin on the way down leaving a nice evident cut in it's side. Yet, even from a mach 3 turn and a major component collision, all three fins remained intact and pretty on the ground. The game does indeed become harder though with 4" versus 3" at mach 3. Every bit bigger the fins are is more aerodynamic loading. Thicker tip-tips and cores are the answer 4" try with adjusted approaches? Ill get the cams ready!!

 

[markkoelsch]

Y'all are too much. The requisite skills to build a 3" min dia are no different than those to build a 4" min dia, and Alex is looking to apply what he learned last year. The reality is that neither project is super challenging.

Just because he's exposed himself to criticism by posting his project on a forum doesn't make it any more or less safe than any other project where the opinions of strangers weren't solicited. The fact that his own self-deprication, which is a refreshing change from all the OpenRocket experts around here, is what led to the criticism is the cruelest irony of all.

Alex - if Mat and I decide to buy stock in Red Bull and I quit my job, we should have our case bonded finocyl done by Aeronaut, but XPRS is looking more likely at this point. Build on and have fun-

I asked a reasonable question. I was not rude not insulting.

You sir need to calm down a bit I think.

 

[Aksrockets]

Lets roll. Ugh, that's a terrible joke.

5 wraps of 3K carbon. HTR-212 epoxy. Turned out lovely.


*makes rocket noise*


Before one of you comments on fin thickness, let me confirm your fears. It's 1/16th. I can hear you already "but Alex! 1/16th isnt enough for a 98MD core". Hush now. You don't know my plan. Or just how bad a** this 1/16 plate is.

Huge thanks to flynfrog for the carbon plate donation. I owe you my first born now or something, right?
The plate is 1/16 BMI high modulus carbon. It's a test panel for the composite parts that go into the Lockheed Martin F35. I can just barely get it to flex along it's 4in span (maybe a millimeter or so) and It'll only get better from here. I have yet to post cure them.

Alex

 

[markkoelsch]

Not familiar with htr212 epoxy- who makes it?

The fins also cool. I wonder what that plate would cost if you had to purchase it.

I am thinking we will see some tip to tip carbon as well? If not, how are you going to keep it together?

 

[Aksrockets]

https://www.aircraftspruce.com/catalog/cmpages/htr212resin.php
Its my new favorite epoxy. Reasonably high TG without the pricetag. Yes, I'll be doing T2T, but the fins still have a long way to go before they'll be bonded to the tube.

And speaking of bevels.

My high tech beveling jig. This actually works very well.


See!




Now I just have to wait for my carbon and nosecone to show up.

Alex

 

[stealth6]

Alex, see your pms.

s6

 

[butalane]

Can I ask a silly question to the thread as a whole. Why would you build a bigger one if the smaller one did not work? It would make sense to get the smaller one working first so you know your design and techniques are sound before going larger.

Last years project failed because the FW nosecone was not up to the task - no suprise seeing the fiber angles - here's to hoping that gets ditched this year. The hard part, fins attached, was wildly successful

The requisite skills to build a 3" min dia are no different than those to build a 4" min dia.... The reality is that neither project is super challenging

Maybe when flying toy rockets, but for optimized flying cases this couldn't be further from the truth. Mach 2 and Mach 4 are wildly different velocities and everything that comes with them make 4in a much much more challenging playing field.

 

[A5tr0 An0n]

Last years project failed because the FW nosecone was not up to the task - no suprise seeing the fiber angles - here's to hoping that gets ditched this year. The hard part, fins attached, was wildly successful

Interesting. I thought it failed because of

So long story short, it was a "shred" caused by instability. As you may have heard, Manny's M2160 burned in only 1.9 seconds, making it about an ~8000ns M4200. My rocket accelerated well past the velocity I simulated (mach 2.7).

Unfortunately, Alex’s rocket was not design to handle such speeds, and went dynamically unstable due to Cp shift at the end of the burn.

as was originally stated in a post flight report from both Alex and Manny and the cone destruction was a direct cause of the instability. I know they were originally expecting a 3.8s burn which would have resulted in a different flight profile.

Is this not what happened? Sorry I have not kept up with the thread so I could have missed that update.

 

[prophecy]

Last years project failed because the FW nosecone was not up to the task - no suprise seeing the fiber angles - here's to hoping that gets ditched this year. The hard part, fins attached, was wildly successful



Maybe when flying toy rockets, but for optimized flying cases this couldn't be further from the truth. Mach 2 and Mach 4 are wildly different velocities and everything that comes with them make 4in a much much more challenging playing field.

I fly toy rockets, AKS flies toy rockets, and this forum is about toy rockets, so that's the experience I'm drawing from, you're correct.

You don't fly toy rockets, but that doesn't mean you need to patronize a valid point I've made. This project won't hit Mach 4 or close to it. In fact, the projected max velocity is awfully close to the max velocity his project reached last year when Manny's motor cranked, hence my point that Alex is using this project as an opportunity to leverage last year's learnings on requisite construction methods and troubleshoot appropriately.

 

[Aksrockets]

I got the nosecone.


Alex

 

[REK]

Just my opinion, but I'd recommend reducing the fin span a bit more. It would reduce aerodynamic loads and drag on the fins.

 

[mannyskid]

Just my opinion, but I'd recommend reducing the fin span a bit more. It would reduce aerodynamic loads and drag on the fins.

Yeah, but then you get a rocket that's unstable. This rocket won't be going that fast, I doubt it'll break Mach 3 so fin strength isn't much of an issue.




In other news, the motor works, I'll post the video later tonight.

 

[BLKKROW]

Just my opinion, but I'd recommend reducing the fin span a bit more. It would reduce aerodynamic loads and drag on the fins.

I think Alex is more worried about stability than the drag and fin flutter. If I remember correctly PWF 1.0 failed due to the motor being aggressive and causing instability.

Since Alex is using a similar formula (I presume), he may be adding a larger fin span to help with stability in order to reduce the chance of the same failure. Plus as he mentioned above the plate he is using for the fins is incredibly tough.

Manny beat me to it.

 

[mannyskid]

Last years project failed because the FW nosecone was not up to the task - no suprise seeing the fiber angles - here's to hoping that gets ditched this year. The hard part, fins attached, was wildly successful

The leading theory to why the nose cone cracked last year was that the tip pulled out (washer, bolt, parachute and all). My 3" project last year used the exact same FW cone and was successful to M3.2, the only difference is that I had a custom tip with a shoulder. Whether the tip pulling out was the cause or the effect of the sudden change in alpha, I think a shouldered tip is in order for this project.

But I'm not making any final calls on the rocket itself, I'm just a motor man...

 

[REK]

Yeah, but then you get a rocket that's unstable. This rocket won't be going that fast, I doubt it'll break Mach 3 so fin strength isn't much of an issue.




In other news, the motor works, I'll post the video later tonight.

Well was just for increasing performance, without the cost of it going unstable.

Its hard to see the calibers in the photo, but assuming you have at least 2.3 or probably more. Shaving a bit of fin span wouldnt hurt.

At any rate, was just an opinion, if you guys feel its not safe to go lower then trust your instincts.