Documenting my Level3 and for sharing with my advisor.

Discussion in 'High Power Rocketry (HPR)' started by TimothyG, Feb 2, 2019.

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  1. Feb 2, 2019 #1

    TimothyG

    TimothyG

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    Had a final conversation today with my advisor on some last minute details for planning my level 3 build and attempt this up coming fall. In order to both get help with my build if needed and to share what I"m doing in one location, I'm going to try and do a build thread on here.

    Major weakness's in my plan. I don't know how to do a fin analysis for flow or flutter. My simulation skills are severely lacking. I'm recovering from health problems that limit my activity. I'm meh at welding aluminum but have friends that are artists in aluminum. My understanding of program is severely limited.
    Strengths I can machine easier then I can eat or drive. I'm a college student with access to machines and facilities I wouldn't normally have access to for design, testing, and manufacturing. All my electronics and components have been spread out over the last year so I'm reasonably prepared and familiar with the components.

    Rocket design is a 98mm minimum diameter rocket using head end deployment similar to the avalanche arrangement. Motor retainer will be integrated into the aluminum fincan and shock cord attached to eyebolt in forward closure of motor. Electronics sled will be a 3D printed unit with individual cell like locations for electronics and batteries with channels run through out for wiring retention and protection. Traditional all thread rod connecting the two bulkheads with bulkheads each having a pair of charge tubes. Main parachute will be housed in a packing tube inside of the nosecone or resting on forward bulkhead depending on packing testing in the coming weeks. I've already decided to do green flames fading to black forward section and thanks to sticker shock that has already been made a reality. Final flight of the airframe will hopefully be at blackrock if everything goes will on a CTI N green motor. If stickers survive that I'll display it at my university engineering atrium until graduation or longer. If they bubble or burn I'll re-vinyl the airframe and display.

    Solidified plans.
    Electronics, power, airframe, motors selection, parachutes and harness's, deployment, data.

    For electronics for deployment I'm running a pair of RRC2+ altimeters that have already flown several times and have proven themselves reliable and easy to use. I will also have an eggtimer proton on board for data collection as this meets my requirements for planning my flights as I move up in motor size to better match my sim and actual altitude. Two camera's will be mounted into the same sled as other electronics to try and record my flights. I just finished playing around with my eggfinder tracker unit while on vacation and hope to get better with it during my shakedown flights. An ARS audible beacon for back up in case rocket lands somewhere awkward and out of site(example is in a wadi).

    Power will be with lithium batteries all around of various mah sizes and voltages depending on device. Wiring will be restrained 100% on sled through printed channels in the sled.

    My pie in the sky dream is to get my certification on a metallic or dark matter motor from Aerotech as I have certified on their motors so far and love them. My primary local vendor already has my motors on order and is looking out for them for me now so I"m not chasing motors the week before. The work up flights will be two different K flights at my local field one to test general subsonic air worthiness another on the K2000 to test the strength of the air-frame and altimeters. My advisor has requested an L flight so I'll also be flying at least one L1000 in this airframe before my level 3 attempt.

    I'll be running a used fruity chute iris that I have if it's appropriately sized but this is to be determined after mass of fincan is more solidly known. I have existing collection of great condition harness's I've used before and that I trust. a single fruity 18" drogue from apogee will be used. then main at 2000ft altitude to allow GPS a longer time to reacquire and accurately broadcast before loosing it on landing.

    I've previously made elongated charge cups out of aluminum and will be making some guntube style charge cups that I've seen here on the forum. I might make these charge tubes breach loadable with pre-prepaired ejection charges in rimmed cases with epoxied in ignitors.

    I've had a bad history of using simulations and as such I'm hesitant to trust altitude predictions for this rocket until after I fly it on smaller motors and dial everything in. This is where the proton will come in handy as I hope to get three different altitude data points as well as velocity data to compare to the simulations in Open Rocket to better dial in the performance of my rocket. This will also be an opportunity to get comfortable with the wifi eggtimer system as well as the safety systems of the proton without actually having it hooked up to charges.

    Flexible idea's/plans
    Fin can plan currently has three design options.
    I can do a welded aluminum fincan and have the aluminum stress relieved and heat treated after(expensive).
    I can machine a multi piece aluminum fincan(This option is cheap and only costs me my time).
    I can braze fins onto a tubing section(this option is doable on my own without assistance but I have the least experience in this.)

    I've received solid permission from my advisor as well as several of the RSO's where I fly to use an aluminum fincan on this rocket on the condition that I produce the fincan myself with zero off the shelf parts and proceed with the planned work up flights.
     
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  2. Feb 2, 2019 #2

    jimzcatz

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    I've said it before and I will continue to say it over and over. Why do complicated for a cert flight, especially L3? Welding aluminum? Fin flutter and flow analysis? Seriously dude? Yea, you can attempt all this, nothing in the rules says otherwise but why? Get your cert on a big heavy rocket then go nuts with the crazy stuff. Minimum diameter in any cert flight is just down right ludicrous. I've said my piece. I'm not alone in this thinking either.
     
  3. Feb 2, 2019 #3

    GRIFFIN

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    I think what Jim meant to say was ......

    Have fun! Good luck!!

    This isn’t your L3 flight, Jim. Not everyone wants to do things “slow and low”

    If he has 2 TAPs that are approving his design, he’s doing things by the book. If he fails, he’ll learn a lesson on his own. Minimum diameter flights can definitely be more of a challenge. I personally like to see people pushing the limits of what’s “normal”

    Not everyone needs to L3 on an 4” rocket with a 3” hole
     
    Last edited: Feb 2, 2019
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  4. Feb 2, 2019 #4

    Rail Dawg

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    The Level 3 certification isn't the pinnacle of personal rocketry research.

    It's the beginning of a long learning process.

    Build a BDR (Big Dumb Rocket), get your Level 3 then start to push the boundaries.

    But if you decide to do otherwise have fun!

    Chuck C.
     
  5. Feb 2, 2019 #5

    jimzcatz

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    No, that not what I mean. I will say good luck and have fun AFTER your cert flight. Like I said, this is my opinion. Carry on.
     
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  6. Feb 2, 2019 #6

    FredA

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    I say KUDOS to the OP for wanting to LEARN SOMETHING while doing his L3.

    You've got two [supposedly] very experienced people mentoring this one and only flight.

    Learn to fly AND RECOVER safely while you have the mentors time and mindshare.
    Get the complicated right.
    Fly the BDR some other time.

    Telling people to purposely fly a BDR so they can SKATE through the cert process is doing a disservice to the hobby. We ALL should want everyone putting up a rocket, especially a big rocket, to have proven competence.
     
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  7. Feb 2, 2019 #7

    Steve Shannon

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    I disagree, Fred. The time for the majority of the learning is before taking the test. I know of no Prefects, TAPs, or L3CC members who would not help anyone at any level as they learn. The certification process at each level is for a flyer to demonstrate that he or she has gained enough expertise and knowledge to be allowed to begin working with greater impulse.
     
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  8. Feb 2, 2019 #8

    FredA

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    "The certification process at each level is for a flyer to demonstrate that he or she has gained enough expertise and knowledge to be allowed to begin working with greater impulse."

    So why a BDR???? Why not something that actually demonstrates level-appropriate competence?
     
  9. Feb 2, 2019 #9

    Andrew_ASC

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    I personally had enough of motor eject BDR after L1. So in my L2 cert I’m going 54mm MD.
     
  10. Feb 2, 2019 #10

    TimothyG

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    To address this I have already flown M motors on several occasions in rockets I built using methods I came up with for our university team. I’m not starting into level three certification process with zero experience. It’s not a lot of experience but it’s not zero either. And I personally have a habit of not doing things the easiest way possible. Every time I have taken short cuts and easier pathways in life I’ve regretted it in some manner. My level three initial design was another big slow M. However I would never fly it again as I live to advance a little further every time I do something. So doing minimum diameter allows for a challenging level three and for further challenges in the future.
     
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  11. Feb 2, 2019 #11

    boatgeek

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    I applaud taking the more rewarding route even if it's not the easiest, as long as you're willing to accept the increased risk of failure. Since you seem to be down with that, more power to you. If you have time and access to machine tools, you can do a lot of fun stuff.

    The only thing I'd worry about a little bit is that you don't feel that you're very strong on the simulation front. I don't worry so much about fin flutter* or flow analysis, but I feel that an L3 should have a good handle on OpenRocket/RockSim/RASAreo and know the limitations and benefits of each.

    *For fin flutter, you can do analysis or you can look at what other people have built and flown successfully. I am a lot more suspicious of analysis than my lying eyes. If you're worried, you can add a bit to your fin thickness.
     
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  12. Feb 2, 2019 #12

    Steve Shannon

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    There’s nothing at all wrong with that, in fact I think it’s important to want to advance with each project. Have you built and flown minimum diameter rockets before?
    Why do you want to make this of metal?
    Here’s the Tripoli policy on metal in rockets:
    http://www.tripoli.org/Portals/1/Documents/Safety Code/Metal in Rocket Construction v2.0.pdf
     
  13. Feb 2, 2019 #13

    TimothyG

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    Only the fin can will be aluminum. Airframe is 60” section of Madcow fiberglass. I initially thought of going carbon fiber but decided against it in favor of something more Rf transparent.
     
  14. Feb 2, 2019 #14

    EeebeeE

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    There are a number of people here who suggest you take it slow, build a big dumb rocket and get through your L3. That's fine and good, and it helps you get the process out of the way ... BUT ... It's YOUR L3. If you want to take it to the extreme, do it. Just know there are risks involved and the more complicated, the greater the risk.

    It took me 3 tries to get my L2. First try the main failed to deploy. Second try, I put too big of motor in it and shredded it. On the 3rd try I succeeded with a LOC Nuke Pro Maxx, I broke Mach 1 and sent it 8,500' up ... kissing the 9,000' waiver.

    Then It took me 3 tries to get my L3. First time I tried using a CTI M2250 and it CATOed on a scratch-built rocket. I fixed that rocket, and tried again. That time the main got tangled and never came out of the chute bag. What parts could, bounced about 15' in the air when they hit the ground. On the 3rd try with a Rocketry Warehouse Terminator and a 5-lb. ballast to hold it down, I succeeded. By that time I had simplified all I could.

    With your experimentation you will create more opportunities for failure, but you will learn, and you will try again if you fail. It's no big deal really. It's only money and time invested. Again, it is your Level 3. Enjoy it Savor the build, and learn from it.

    Also ... Download FinSim. It is a great and easy to use fin flutter analysis tool.

    Good luck.
     
    Last edited: Feb 2, 2019
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  15. Feb 5, 2019 #15

    Ez2cDave

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    Why NOT a "BDR" ?

    Advantages of the "BDR" :

    (1) Safety & Reliability

    (2) Less complex - Lower risk of failure, higher chance of success

    Disadvantages of the "BDR" :

    (1) People don't get to "show off" and "stroke their ego" . . .

    (2) Certain people will "look down on you" because you didn't "pay your dues" by flying a "balls to the wall", minimum-diameter, mach-busting rocket, festooned with every piece of high-tech electronics you can cram into it . . . ( The same mentality permeates Ham Radio, where "No-Code" Licensees are snubbed by "Old-School Elitists" who had to learn Morse Code and be able to send and decipher it at high rates . . . God forbid if you ever admit you came to Ham Radio from CB ! ).

    When I do my Level 3, it will 100% my own design, with no exotic materials used anywhere. I intend to keep the velocity sub-Transonic and fly with a "Baby M", like the Aerotech M650 Moonburner. In a 30lb, 5" diameter rocket it will reach about 8400ft with a maximum velocity of only 660 ft/sec ( 450 mph ). My rocket will weigh around 25lb, 10ft tall, 5.5" diameter ( un-glassed Blue Tube 2.0 ), using two RRC3+ units ( no other "toys" ) . . . Nice and simple !

    Dave F.


    BASIC PERFORMANCE.jpg
     
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  16. Feb 5, 2019 #16

    Ez2cDave

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    Jim,

    Well said, sir . . .

    I agree with that philosophy 100% !

    Dave F.
     
  17. Feb 5, 2019 #17

    Nytrunner

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    With due respect, I felt that come off as a little harsh/condescending

    This is an amazing hobby with so many paths upwards in the impulse levels. Why the need to look down on someone because their path doesn't follow someone else's philosophy? (provided they're technically competent and designing with a mind to safety)

    A low and slow level 3 is perfectly fine. Strength and build skill must be demonstrated to make a rocket that survives and recovers. If that is the profile and challenge a flier wants in their level 3 certification, then more power to them!
    A minimum diameter screamer level 3 is also perfectly fine. Not everyone is capable of it, and not everyone gets enjoyment from it, but if that is the flight profile and challenge a flier wants in their level 3 certification, then again more power to them!

    We're fortunate that the certification process is so flexible, and that we have TAPs/L3CCs that will work with a candidate on an as needed basis (some will need more guidance than others).
    I enjoy seeing the Low/slo's on a big motor (Ted Cochran, Steve Lubliner, Nick@Jet etc..), and I enjoy seeing the videos and stories of folks that go to blackrock for their min-diameter L3's (JimJ, Astro-Anon, Pete from my club, and now TimothyG right here!). It's all rockets, and it's all great!

    Let's be encouraging and learn from folks that do things differently (and safely)!
     
  18. Feb 5, 2019 #18

    cherokeej

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    Ah, rocketry. Seems once again, there is no ONE correct answer.

    I have spent time on the L3CC. I think it's up to the individual flyer and his/her cert team.

    One flyer might want a big, heavy 3FNC, baby M, pop at the top, and get an autograph. It works. Get a great big 3 on that card.

    The next candidate has access to a 6 digit waiver, and feels confident in using a major portion of it. If he feels good about it, and his TAPs feel good about it, I say Up Fast and Down Slow! Make it happen!

    Just remember... At L3, you are expected to engineer failure completely OUT of the equation. And flying a 98mm MD on N impulse at Black Rock is not for the faint of heart. You've gotta bring it back in one piece.

    I was going to type "best of luck." But I already said you're engineering failure out of the equation. So there should be no "luck" involved.

    We'll all be watching at XPRS.
     
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  19. Feb 5, 2019 #19

    cbrarick

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    I don't care what you fly....find your own way.

    However "doing things the hard way" is how MANY university teams have gotten into trouble. I'm not going to name names, but we all know them
    There's a reason why all the really "cool" projects are still doing things the easy way - it's called reliability.

    Why do you want an aluminum fin can? You clearly don't have the capacity to manufacture it. Brazing on fins has never been done, and for good reason. We've seen krylon high heat paint burnt off on big MD projects (1200 degrees) and you want to use a filler that is fluid between 1150 and 1550 degrees. What temp will it loose the strength needed to keep the fins on? Is there any data? Half that? Who knows?

    If you've never welded aluminum you need to know not only do you worry about the heat treat, but it's pretty easy to warp your fins. Aluminum is one of the more difficult metals to weld (of the ones easily obtainable, yes I know that there are many difficult exotic metals). Cause it's your L3 you can't sub out that part.

    A multi part one is interesting, but you gotta figure out how to mechanically connect a really thin fin to a tube without screwing up the profile. AND make it strong enough


    Instead, scrap what you don't know and work with what you do. People have been surface mounting fins on MD rockets for a long time. It works, and has been proven so over and over.....


    so, i've assured myself of some hates and likes.....do what you want but you might want to engage the usual RSO at whereever you're gonna fly this that your method is sound, after all they have to OK the flight or it sits in your car.
     
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  20. Feb 5, 2019 #20

    cwbullet

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    I usually tell folks seeking advice to build within your skills. It is good to challenge yourself, but it also a great idea to stick to some of your strengths. If machining is a skill, use it, but keep the metal to place you need it. There is no reason to make a ground penetrator.
     
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  21. Feb 5, 2019 #21

    Bat-mite

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    Always amazes me that people are so gung ho to tell others what to do for their cert flight, especially when they didn't ask, no matter which side of the argument you're on. If people had jumped all over me when I posted about my rocket plans, I probably would not have come back to the forum.
     
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  22. Feb 5, 2019 #22

    cwbullet

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    If you do not want suggestions and advice, I would say you might be in the wrong hobby. We are a sharing group whether you want it or not. A better hobby for someone that want to post what they are gonna do without suggestions is becoming an island hermit.
     
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  23. Feb 5, 2019 #23

    Bat-mite

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    I see a huge difference between someone saying, "Here's what I'm thinking about doing; what do you all think?" vs., "I am documenting my plans for my advisor," and not asking for opinions.

    But then I guess I am doing the same thing, since no one asked me for my opinion about whether or not they should post their opinions. :oops:

    Carry on! Good luck with your L3, TimothyG!
     
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  24. Feb 5, 2019 #24

    Andrew_ASC

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    And a certification with a BDR is a certification. It’s just me personally got more thrills out of the minimum diameter flight profile than a BDR. And what really tickled my interest was university level 1 min diameter multistages that were on the edge of waivers with $60 of Propellant.

    The sense of satisfaction wasn’t the same. One was like yuppie and the other was just exhilarating when it worked. I dunno just rambling. I don’t look down in a BDR it’s really economical and such.
     
  25. Feb 5, 2019 #25

    mccordmw

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    For your fin can, you might want to check out Binder Design.

    http://binderdesign.com/store/page13.html

    Those will definitely stand up to a 98mm min. diam. flight.

    I'm just not sure about his turnaround time at this moment.
    *Edit: I missed it, and it's right near the top in bold. :p Expect a 3 week turnaround time.*

    If you don't want to go the commercial fin can route, you might consider bolted on fins instead of welding. The bolt-on route is tried and true.

    I hate how I keep posting links to my L3 documentation. It feels like I'm pimping it out and bragging, but I'm not. Anyway, if you want to read up on how I did my fin flutter analysis, it's in there.

    https://drive.google.com/open?id=1i4anunZXsiG7dyIP78nmFN7WJrSK-7uAgVvensHU9ok
     
    Last edited: Feb 5, 2019
  26. Feb 5, 2019 #26

    Bat-mite

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    OP's last sentence: "I've received solid permission from my advisor as well as several of the RSO's where I fly to use an aluminum fincan on this rocket on the condition that I produce the fincan myself with zero off the shelf parts and proceed with the planned work up flights."
     
  27. Feb 5, 2019 #27

    mccordmw

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    I never claimed to be good at reading comprehension. :p

    Kind of a curious requirement, though. Kind of like saying yeah you can use a nose cone, but you have to learn how to turn one on a lathe and do the fiberglass layups. But hey it's his TAP team, I'm sure they know what they're doing.
     
  28. Feb 5, 2019 #28

    boatgeek

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    I don't think this is "hate" but I do think you've gotten something wrong here. The OP says that he has good friends who can weld well. What's the difference between asking a friend to weld up fins you designed to a fin can ring that you designed and buying an aluminum fin can off the shelf from Binder? As far as I can tell, both would be acceptable on an L3, provided that the L3CC/TAPs are satisfied with the workmanship. Nobody was even talking about brazing on fins before you brought it up.

    Seriously, people, why is it so hard to wrap your head around the idea that different people cert in different ways and that there's 5000 ways to skin this cat? As long as the flyer has engineered a safe flight to the satisfaction of the certification team, it's none of my business how they did it. Yeah, it's not the way I would do it, but the OP seems to understand that it's a riskier approach with higher personal rewards and I'm not going to yuck their yum.
     
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  29. Feb 5, 2019 #29

    TimothyG

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    NAR rules dictate that you can’t use a commercial off the shelf fincan for your L3. It does not however say that you can’t use a fincan. I had to clarify this before making my decision.


    My understanding, and I agree, is that they don’t want people doing a pure bolt together L3. They want me to invest time and effort. I’m ok with this.
     
    Last edited: Feb 5, 2019
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  30. Feb 5, 2019 #30

    TimothyG

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    And for future reference people have brazed on aluminum fins and flown them above mach2. I actually read about that here.
     

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