Sparrow from Arkansas [Uncle Mike's Rocket Shack]

[Rktman]

Better to answer with a pic:

View attachment 372683

Cool! (I'm a "show me" vs a "tell me" guy) so I understood immediately. Makes so much sense once it's drawn.

 

[Crawf56]

Something like a flap, or a leading edge slat, or even an aileron, changes the shape of the airfoil to generate more (or less) lift.

But on this small rocket glider, I don't have that option.

So, I am making small changes to the airfoil shape on the right wing to get the glide performance that I want. But I am now worried about my rocket performance.

 

[Crawf56]

NOTE: When I test a new model like the Sparrow, I go to an abandoned WW2 training airstrip here in northeast Arkansas. It looks like a wide dirt road surrounded by soybean fields.

I make sure that I do my rocket tests where no one can get hurt.

 

[Rktman]

Something like a flap, or a leading edge slat, or even an aileron, changes the shape of the airfoil to generate more (or less) lift.

But on this small rocket glider, I don't have that option.

So, I am making small changes to the airfoil shape on the right wing to get the glide performance that I want. But I am now worried about my rocket performance.

Free flight is always more...worrisome?...uncertain?... nerve-wracking? Let's just's say more...er...exciting than RC in that way (isn't it true you can get almost anything to fly with RC control?). Without a pilot you are never absolutely sure what your rocket glider will do once you launch it. At least it keeps things interesting. That's one reason why I want to get into RC. Too many of my gliders go AWOL. At least with RC control you're pretty much assured of getting it back.

 

[Rktman]

NOTE: When I test a new model like the Sparrow, I go to an abandoned WW2 training airstrip here in northeast Arkansas. It looks like a wide dirt road surrounded by soybean fields.

I make sure that I do my rocket tests where no one can get hurt.

Wise move. Sounds ideal. My only option is a largish park that has a habit of gobbling up 40% of my gliders and the occasional rocket. (I'm not alone on that count though, at least a few of the park trees will have strange fruit with fins or wings on them every time I go). Never a dull moment though.

 

[Crawf56]

Conducted two launches today on my Sparrow.

Both launches were the same:
- Good launch, straight up (FAST!)
- Motor ejected, looked good for a moment...
- Then the right wing dipped, and the Sparrow made a rapid circling decent to the ground.

Despite the speed at which the glider hit the ground, it appears to be undamaged.

Did a few fingertip balance measures, and sure enough, the Right Wing is heavier (you called it, Rktman).

So the current plan:
- Get the model balanced laterally (wingtip to wingtip).
- Then re-evaluate glide performance.

 

[Crawf56]

Ok, time to play the balance game. Note how the glider is leaning to the Right Wing. I also tried balancing with a rod, got the same thing.

 

[Crawf56]

Added a little clay out on the left wingtip. Looking better...

 

[Crawf56]

Attached the clay to the left wingtip (underside).



.

 

[Crawf56]

Did a quick glide test tonight (flashlight in one hand, glider in the other).

Seemed to have much improved glide performance. Stalling some, though. I think my Sparrow needs a little nose weight.

By the way, the clay that comes with the Sparrow kit is fantastic.

 

[Crawf56]

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

Very sorry, kuririn; realized I had neglected your questions.

COLORS: The white is Testor Model Master spray enamel paint. The fluorescent orange is "safety orange" from a hardware store.

AIRFOIL: Think I answered this in Post# 30. Trying to get it to turn, slightly.

 

[cwbullet]

That birdie is more of a GA Mosquito.

 

[kuririn]

No worries. We launch on a smallish field here so trimming gliders to come down in a shallow spiral is necessary also. And less time spent recovering means more time launching.

 

[Crawf56]

That birdie is more of a GA Mosquito.

Being surrounded by rice fields in northeast Arkansas, I about fell over when I read this. Well played, sir.

I went to Auburn University (in Alabama, near Columbus, Georgia/Jawja), and had a friend that went to Warner Robbins for his first job. He said the main way to lookout for Georgia mosquitos was their SHADOW!

He also said that, what he liked most about Georgia mosquitos was that there was no limit.

That was about 25 years ago...….

 

[Crawf56]

The good news is that, my Sparrow glides much better. The bad news is that it is gone.

Here is a video of the launch. Flying with an A8-3, you see the pop from the ejection charge at about 12 seconds.

At about 14 seconds, there is a faint white dot moving right to left in the lower left-hand side of the video screen. The white dot is near the left edge, about 3/4's of the way from the top of the frame. (Almost at a 45 degree angle from the "pop" smoke, to the left and down). My original video is a little better quality.

EDIT: You have to have the video on full screen mode.

 

[Crawf56]

Remember that the top is white and the bottom is orange. It is 8 am, with the sunrise to the right of the video. Very slight south wind; the video is facing north/northeast.

Dang it. Even went back out at around 2 pm; nothing.

To add insult to injury, I realized I had forgotten to put my phone number on the model.

 

[georgegassaway]

Gliders usually like to have an airfoil.

Especially flying wings.

I do not see how this flying wing model is supposed to glide reliably, without some "up elevator" tabs along the trailing edge.

Note that the old Estes Nighthawk, the downturned winglets served both as rudders AND up-elevator tab (not angled down at 90 degrees like this model). Note that the joint line between the main wing and tips is angled, not parallel, causing the downturned tips to be at a different angle of attack to the air than the main wing (a few degrees down angle of attack compared to the main wing, acting as up elevator effect). That is the only flying wing without true elevators (or reflexed airfoil) that comes to mind, among reliable models, anyway.
Shown with pop-pod attached (not my model):

The old SAI Mini-Bat had small elevators, at the wingtips. I built one in the early 70's. Had a nice fast flat glide. But the boost was not straight.

 

[kuririn]

The good news is that, my Sparrow glides much better. The bad news is that it is gone.

Oh no, after all that hard work! That's a problem with the tiny rockets. Can't tell you how many Mosquitos and Streaks I've lost over the decades, even with fluorescent paint on. But looks like the boost was straight. Are you going to rebuild?

 

[Rktman]

Ouch! I know how that feels. Sorry to see it got away from you.
If you order a replacement kit, at least you'll know that the build will be faster/easier after what you learned from this one.

 

[Crawf56]

Oh no, after all that hard work! That's a problem with the tiny rockets. Can't tell you how many Mosquitos and Streaks I've lost over the decades, even with fluorescent paint on. But looks like the boost was straight. Are you going to rebuild?

Yes, I am going to build this kit again, but will likely be later this year. It only cost $15, so it is not a big investment.

I feel like I got this kit somewhat figured out. Will only use 1/2A6-2 (18mm).

By the way, might get two kits, and try to make a 13mm motor work.

 

[Crawf56]

I do not see how this flying wing model is supposed to glide reliably, without some "up elevator" tabs along the trailing edge.
Note that the old Estes Nighthawk, the downturned winglets served both as rudders AND up-elevator tab (not angled down at 90 degrees like this model). Note that the joint line between the main wing and tips is angled, not parallel, causing the downturned tips to be at a different angle of attack to the air than the main wing (a few degrees down angle of attack compared to the main wing, acting as up elevator effect). That is the only flying wing without true elevators (or reflexed airfoil) that comes to mind, among reliable models, anyway.

I think this model is similar: The angled wingtips help promote the desired performance at launch and glide.

 

[georgegassaway]

Oh. Other photos looked to me more like the joint at the tips was parallel to the root, and the tips angled at 90 degrees. Sorry you lost it. What engine?

 

[Crawf56]

Oh. Other photos looked to me more like the joint at the tips was parallel to the root, and the tips angled at 90 degrees. Sorry you lost it. What engine?

I was using an A8-3. The kit recommends a 1/2A6-2 or an A8-3. I was using the A8-3 because the 1/2A6-2 was not available at the local Hobby Lobby. (I try to support local merchants when I can.)

I am also considering an up-size version of the Sparrow.

 

[kuririn]

Crawf,
More Holverson Designs here:https://www.oldrocketplans.com/hdi.htm
IIRC I think I got my Zoomie from Uncle Mike's. Similar design but even smaller with 13mm motor mount:
https://unclemikesrocketshack.com/Holverson/Zoomie/Zoomie.pdf
An upscale would be easier to track. Cheers.