Sparrow from Arkansas [Uncle Mike's Rocket Shack]

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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
 

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
 

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
 

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
 

Rktman

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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.
 

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:
 

Rktman

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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.
 

kuririn

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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.
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.
 

Rktman

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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.
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?
 

Mr Rocket

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I've always really liked that rocket glider. Maybe someday I'll have to get one.
 

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.
 

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
 
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kuririn

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What did you use for the colors? Sharpies, RIT dye, something else?
 

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.
 

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.
 

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
 

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
 

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
 

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
 

Rktman

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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.
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.
 

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
 

Crawf56

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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.
That is a REALLY good point. Had not thought of that; did not weigh wings prior to assembly. :oops:
 
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