Thoughts on current project 38mm Hi Flier

Discussion in 'High Power Rocketry (HPR)' started by Devin Batten, Jul 13, 2019.

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  1. Jul 13, 2019 #1

    Devin Batten

    Devin Batten

    Devin Batten

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    My first minimum diameter rocket was the Estes Hi-Flier. with the way it went off into the great blue yonder amazed me. Me being ambitious decided I wanted my next project to be an upgraded version. So I present the "Stupid Hi-Flier", cause it'll go "stupid high". Built around a H550


    fiberglass body tube
    6"x76" streamer for recovery
    fins are 1/8" plywood


    .rkt found here
    https://drive.google.com/open?id=1aOwN1q5DfiGajl7P3TzRXPe_WdG6gyb4


    Looking for feedback from the more "seasoned" fliers
     

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  2. Jul 13, 2019 #2

    manixFan

    manixFan

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    If you want to start doing high flying MD rockets, you need to think about tracking. I used a small RDF beacon for many years, which worked well but took time to find the rocket. Now I use the Featherweight tracker which will fit into a 29mm nose cone. The GPS output lets me very quickly recover the rocket. The other issue with MD rockets is keeping the fins on. If you are going past Mach, you need to make sure to avoid fin flutter - it has been the death of many rockets. A swept clipped delta shape is a good starting point. The other thing is making sure you have figured out how to do a good surface mount to keep them on. Your shape is a good starting point. But consider adding a layer or two of fiberglass. Going past Mach with plain plywood may be a challenge.

    I fly a lot of MD rockets, it's really not as hard as some folks make it seem. But you do need to pay attention to your fins make sure you keep them on.

    Good luck,


    Tony
     
  3. Jul 13, 2019 #3

    jlabrasca

    jlabrasca

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    Do you have your L1 certification?

    It looks like you mostly scaled up the Estes kit?

    The wall thickness on your airframe is less than a millimeter.

    Have you sourced the nosecone?

    https://www.rocketarium.com/Build/Nose-Cones/1.6-4?cPath=19_209&

    What are you planning for motor retention?

    Edit: According to the simulation (running in OpneRocket), you will go supersonic on an H550.
     
    Last edited: Jul 13, 2019
  4. Jul 13, 2019 #4

    Flyfalcons

    Flyfalcons

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    The fins are on the larger side for the speeds you are planning (this is common when doing direct upscales of smaller rockets) and 1/8" plywood. You might want to run Fin Sim to check for potential flutter issues. Perhaps consider switching to 1/8" G10 fiberglass if it looks like the ply might not hold up.
     
    YodaMcFly likes this.
  5. Jul 13, 2019 #5

    Devin Batten

    Devin Batten

    Devin Batten

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    Yes I am an L1
    Yeah, that was the intention was to make a big boy version of it.
    Yeah, for some reason when i save certain details it doesnt keep i.e. streamer length
    I am looking for a source for the nosecone if not ill end up changing it, or making one.
    K clips for the motor retention.
     
  6. Jul 13, 2019 #6

    Devin Batten

    Devin Batten

    Devin Batten

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    Ill have to do that. Always in the market for new ways to test before putting it on the rail.
     
  7. Jul 13, 2019 #7

    Theory

    Theory

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    For the build I recommend ditching the ply and going with G10. ...3/32 G10 at that.

    Prep the surfaces to perfection and bond with Aeropoxy ES 6209 or better

    Then let her rip
     
  8. Jul 14, 2019 #8

    David Schwantz

    David Schwantz

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    Devin, good luck with your flight. IMO, as others have stated. Fins are to large, fin material may not be up to mach flight. If you are doing MD, consider friction fitting motor with aluminum tape on the outside. If you go with G10 fins, I like to drill very small holes at the root to help with bonding, rough up all glue joints with 36 grit, use a good epoxy, Rocket Poxy, Aeropoxy, or Hysol 9462. All have good shear strength and will make good fillets. Ditch the launch lugs and use a flyaway rail guide, or tower. Taper all fin edges, including the TE. Make NC bulkhead removable so that you can add or subtract weight as needed. You may need to add weight to get the altitude. Rocket will need to be as smooth as can be, painted, polished, waxed, believe me, it helps. Also paint it red, red is the fastest color :)
     
  9. Jul 15, 2019 #9

    mperegrinefalcon

    mperegrinefalcon

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    Ditch the ply for the fins. Get in contact with Nat Kinsey of Upscale CNC. He can cut the fins out perfectly. (natkinsey@gmail.com). For a 38mm minimum diameter you should be okay with 3/32 G10, and definitely okay with 1/8" G10.

    Looking at your sim you have a max velocity of mach 1.57, and your fins are very tall, giving them a lot of leverage at the tip if they flutter. I can run it through finsim for you if you give me the dimensions. If you want this specific shape of fin I would probably want laminate with a layer of unidirectional carbon facing 90 degrees to the body. I have flown mach 2 without lamination, but that is with a longer root and very short fins, fillets done with RocketPoxy. The reason I recommend the carbon is to hold the fins onto the airframe and to resist torsional forces. With minimum diameter you don't have the leverage of through the wall fin mounting to reduce the stress on the epoxy joint. I would say you definitely should have some sort of active tracking. The Featherweight GPS tracker is really easy to use and doesn't require a license. I have heard good things about the Big Red Bee 900 as well. I personally use a TeleMetrum or TeleGPS with a TeleBT ground station and Arrow 440 Yagi.

    I would suspect that this will fly around 4,000-6,000 feet on the H550, while this is not too high for visual tracking, especially with a reflective streamer and large landing field, but I would choose to get a tracker just to protect my investment in the rocket, it also then opens you up to putting something like an I motor in this too.

    Just my $0.02, wanted to chime in and offer my (relatively limited) experiences with minimum diameters.

    Read this article: https://www.rocketryforum.com/threa...our-government-doesnt-want-you-to-know.58389/
     

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