Sparrow from Arkansas [Uncle Mike's Rocket Shack]

Discussion in 'Rocket Boosted Gliders' started by Crawf56, Jan 18, 2019.

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  1. Jan 18, 2019 #1

    Crawf56

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    Saw this little rocket glider [non RC], and just had to get it. This is from Uncle Mike's Rocket Shack, produced by Wolverine Rocketry.

    m_Sparrow picsmall.jpg
     
  2. Jan 18, 2019 #2

    Crawf56

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  3. Jan 22, 2019 #3

    Crawf56

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    Getting started. Glue the nose cone in the motor tube. It was a tight fit, but not a bad fit. Needed a little sanding.

    m_IMG_3882small.jpg
     
  4. Jan 22, 2019 #4

    Crawf56

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    Getting started on the wings. Nice laser cut wood.

    m_IMG_3881small.jpg
     
  5. Jan 22, 2019 #5

    Crawf56

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    Needs a little sanding to remove burned wood.

    m_IMG_3883small.jpg
     
  6. Jan 22, 2019 #6

    Crawf56

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    Gluing on the wing tips. Make sure you make left AND right wings. And not two left wings.....

    m_IMG_3884small.jpg
     
  7. Jan 22, 2019 #7

    Crawf56

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    Used a small triangle to glue tips at 90 degrees. Not sure this is worth the effort, because you have to hold the triangle and the wingtip on the wing with one hand, while you add glue [CA] with the other.

    m_IMG_3885small.jpg
     
  8. Jan 23, 2019 #8

    Crawf56

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    Gluing the wing halves together:

    m_IMG_3890small.jpg
     
  9. Jan 23, 2019 #9

    Crawf56

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    Adding the motor pod and launch lug:

    m_IMG_3891small.jpg
     
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  10. Jan 24, 2019 #10

    Rktman

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    Eric Noguchi

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    That went together about as fast as my Jet Freak. I like these small simple gliders that are a fast build. They're just the thing to keep busy with when you're waiting for glue, epoxy, or paint to dry on your other builds. Although many people say they are difficult to trim and get flying well, I never had a problem with my Jet Freak. Sadly an overly energetic ejection charge turned it into a cloud of balsa dust over the weekend, never did find anything but 2 small fragments of wing.

    Have fun with your Sparrow, I've had my eye on it for a while too. Interested to see how this small free flight bird does.
     
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  11. Jan 25, 2019 #11

    Crawf56

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    Speaking of difficult to trim....o_O

    Been playing with my Sparrow, trying to get it trimmed out. Got it better, but not good. Added a little nose weight.

    Will post what I did when I get it sorted out.

    EDIT: Been outside tonight, holding a flashlight and tossing my Sparrow. Went inside when I couldn't feel my hands anymore.....:confused:
     
  12. Jan 25, 2019 #12

    Rktman

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    Eric Noguchi

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    Haha been doing the same thing lately.
    One thing I've noticed is that "non-traditional"-shaped gliders (like tailless deltas, flying wings like your Sparrow, and canards) can trim out perfect with hand tosses but fly lousy when launched, or trim out mediocre but glide spectacular after being launched. Haven't figured out what that's all about, but I guess it's true that the real trimming and fine tuning takes place after several shakedown flights.
     
  13. Jan 25, 2019 #13

    kuririn

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    I concur. Trimmed my Zoomie clone till it glided nicely on hand tosses. First flight it did a u turn off the launch rod. Don't know if I'm going to continue working on it or make it a permanent shelf queen.
     
  14. Jan 25, 2019 #14

    Rktman

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    Eric Noguchi

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    I've been wondering if it's related to the fact that hand tossing can't get a glider moving as fast as it is when it's launched and transitions to glide at engine ejection. One thing I've tried is attaching a temporary hook to the bottom of the fuse and launching it using rubber bands attached to a stick, the way HLG (Hand Launch Glider) fliers do it.

    It sure gave me different results than hand tossing it. Only problem was getting it high enough in the air without launching it too hard and giving it too much speed. Rubber launching it out a 2nd floor window at a speed closer to what it would be seeing at apogee would be ideal—but who has the luxury of always having a bunch of retrievers at ground level waiting to recover it?
     
  15. Jan 26, 2019 #15

    Mr Rocket

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    I've always really liked that rocket glider. Maybe someday I'll have to get one.
     
  16. Jan 26, 2019 #16

    Crawf56

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    Good discussion, guys. :cool:
     
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  17. Jan 26, 2019 #17

    kuririn

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    Crawl, did you sand an airfoil in your wings? I sanded one in my Zoomie, I'm thinking that's what made the boost squirelly. Too much lift.
     
  18. Jan 26, 2019 #18

    Crawf56

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    To begin, here is what the painted Sparrow looks like.

    Per my standard procedure for difficult to see models, the top is white and the bottom is orange.

    EDIT: In the "orange" pic, the black stuff near the nose is clay (came with the kit). Also, I have done some sanding on the wing leading and trailing edges. More on this soon.

    m_IMG_3898small.jpg

    m_IMG_3905small.jpg
     
    Last edited: Jan 26, 2019
  19. Jan 26, 2019 #19

    kuririn

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    What did you use for the colors? Sharpies, RIT dye, something else?
     
  20. Jan 26, 2019 #20

    Crawf56

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    When I did my initial glide tests (tossing the model forward by hand), the Sparrow wanted to pitch up, and stall to the right.

    Solution: Added some nose weight. Some black clay was included in the kit for this purpose (pretty good stuff).

    The next set of glide tests seemed to have eliminated the pitching up. But the model would travel 5 feet, and the right wing would drop, sending the model into a right-bank spiral.

    Solution: Sanding on the leading and trailing edges of the right wing, along with some deflection sanding on the winglets out on the wing tips, to try and get the Sporrow more "left" movement.

    The glide tests showed more improvement. I felt I needed to remove a little of the clay nose weight.
     
  21. Jan 26, 2019 #21

    Crawf56

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    So, as of right now, I consider the model to have decent glide performance.

    But glide performance also varies greatly, depending on how much I "push" the Sparrow when I do a glide test. I feel that I am at a point where I need to do a rocket launch, and see how the model responds.

    I am not sure of the glide variations are due to my construction, or due to variations in the wind.
     
  22. Jan 26, 2019 #22

    Crawf56

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    Let's look at some pics. Here is the clay on the nose. The nose is also a little dinged from the glide tests.

    The pic is "upside down" as taken. But the orange-side is the bottom, so I wanted to keep your view more easily adjusted to the correct model orientation.

    Note also the sanding on the lower front edge of the right wing (left side of pic).

    m_IMG_3904small.jpg
     
  23. Jan 26, 2019 #23

    Crawf56

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    A better view of the sanding on the front leading edge of the right wing, trying to get it to deflect upward for glide. Hope I haven't screwed the rocket flight. :eek:


    m_IMG_3899small.jpg
     
  24. Jan 26, 2019 #24

    Crawf56

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    Front view of left wing: no change. The instructions did not say to sand for aerodynamics. I am leaving the left wing with "square" leading and trailing edges to induce drag, and maybe cause a "left turn" tendency in the model.

    Or not. o_O

    m_IMG_3900small.jpg
     
  25. Jan 26, 2019 #25

    Crawf56

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    Here is a look at the top of the right wing. Note the sanding on the trailing edge.

    m_IMG_3903small.jpg
     
  26. Jan 26, 2019 #26

    Rktman

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    Eric Noguchi

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    Everything looks even and aligned. If not wind variation, one wing could be quite a bit heavier than the other. I did a scratch-build where one wing was more than twice as heavy as the other even though I cut both out of the same piece of balsa. I later noticed after I glued everything together that the right wing had a denser, harder balsa vein running through it. Had a heck of a time trying to fix that annoying right pitch and turn.
     
  27. Jan 26, 2019 #27

    Crawf56

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    Here is a view of the sanding on the wingtips. Sanding on the back right edge, trying to get left movement in the model.

    Again, pic is upside down to show proper model orientation.

    m_IMG_3902small.jpg
     
  28. Jan 26, 2019 #28

    Crawf56

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    That is a REALLY good point. Had not thought of that; did not weigh wings prior to assembly. :oops:
     
  29. Jan 26, 2019 #29

    Rktman

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    Eric Noguchi

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    Interesting. What does sanding the trailing edge do to the airflow? Does it increase lift somehow, like a flap?
     
  30. Jan 26, 2019 #30

    Crawf56

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    Better to answer with a pic:

    m_IMG_3906small.jpg
     

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