Slow and Stable?

Discussion in 'Low Power Rocketry (LPR)' started by Murdnunoc, Aug 22, 2019.

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  1. Aug 22, 2019 #1

    Murdnunoc

    Murdnunoc

    Murdnunoc

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    One thing that interests me, as a dad with little guys, is fun rockets that go slow enough for the boys to keep track of and watch the whole flight.
    This leads to rockets that are light and high drag, and a search for long burning motors so the WOW factor is extended.

    I know that 50fps or 35mph off the launch rod is considered a safe rod exit velocity to get the rocket flying.
    Is there a point where a rocket becomes stable enough that this speed could be lower and still have a safe bet of exiting the rod without going sideways?

    It seems a slow rocket with high stability would need very light wind so it doesn't cock sideways as soon as the wind comes a little sideways.
    But given that light wind condition, could it work out OK to use, say, big fat fins and a 4:1 stability?

    Just have the wheels spinning in my head, wanting to maximize the fun and minimize the risk.

    IMG_2152.jpg
     
  2. Aug 22, 2019 #2

    mbeels

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    I think that 50 fps number is a very general rule of thumb, mostly applicable to "normal" rockets. A very draggy, over stable rocket probably falls outside of that "normal" range.

    I also like launching light and high drag rockets slowly for the visual effect. I have one light weight rocket with oversized, draggy fins, and it certainly leaves the rod much slower than 50 fps, but as long as the winds are light, climbs steadily under power and is fun to watch.

    I like that duck rocket!
     
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  3. Aug 22, 2019 #3

    heada

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    Tube fins also work better in wind than normal fins. A rocket that can only be launched in 5mph winds could possibly be OK in 7mph to 10mph winds if you use tube fins instead.
     
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  4. Aug 22, 2019 #4

    GlenP

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    There are some cool saucer type rockets here, and free downloadable templates for smaller motors
    http://www.artapplewhite.com/

    Also there are cardstock paper templates for the Centuri X-24 Bug, a drag body with glider recovery.
    http://www.oldrocketforum.com/showthread.php?t=11007

    Maybe something a little different than what you were thinking, but cool low and slow type flights.

    Maybe give the Mean Machine a try, low and slow on a D engine, but nearly out of sight on an E, take your pick.

    And the Estes Quinstar, upgrade to a 24mm mount?
     
    Last edited: Aug 22, 2019
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  5. Aug 22, 2019 #5

    Murdnunoc

    Murdnunoc

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    Oooh I didn't think about tube fins behaving differently in a crosswind. But I can see it now that you mention it.
    Tube fin rocket is now on the build list.
     
  6. Aug 22, 2019 #6

    Murdnunoc

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    Those saucers and cones are cool. Haven't messed with them, but be fun to try.
     
  7. Aug 22, 2019 #7

    Murdnunoc

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    On the subject of cones, I guess adding a flared out tail cone could bring some additional stability through tail drag?
     
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  8. Aug 22, 2019 #8

    jadebox

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    Yes. I once used a plastic funnel over the fins of a rocket to make a "cone-finned" rocket. It flew well and the cone made the exhaust from the motor look more impressive.



    More generally, short, fat rockets tend to be more stable due to base drag. You often safely fly them on lower-thrust motors for slower lift-offs.

    Also, using a longer rod or rail when going for a slow lift-off may help.

    Finally, check out what Joe Barnard (and others) are doing with thrust-vector control:

    https://www.youtube.com/channel/UCILl8ozWuxnFYXIe2svjHhg

    https://m.facebook.com/watch/?v=307234359893764&_rdr
     
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  9. Aug 23, 2019 #9

    BABAR

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  10. Aug 23, 2019 #10

    Murdnunoc

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    Cool, so between cones, tube fins and generally highly stable, high drag designs, I have some new tools and options to play with now.

    I'm going to see if I can convert that Slo-Mo Dickson file to work in open rocket so I can scratch up something using those design principles.

    Biggest thing now inhibiting slow flight with any kind of altitude is a long burn motor in the A-D range.
    Reloads do open up some possibilities for lower thrust, and I may just get a casing for this kind of stuff.
     
  11. Aug 23, 2019 #11

    BABAR

    BABAR

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    Would be interesting to stage a slo mo clone, with the slo fins on both booster and sustainer.......
     
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  12. Feb 16, 2020 at 11:18 PM #12

    IluvRocketry14

    IluvRocketry14

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    yep, Warlocs, minimaggs, sumo's, Gizmos etc. I love those kinds of rockets.
     

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