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        Discussion Sparrow "BOP-ish" glider

#1 Fly Wheel Nov 13, 2012 02:55 PM

Sparrow "BOP-ish" glider
 
I saw these plans: ( http://www.rcgroups.com/forums/showa...2&d=1325607728 ) on another thread and it immediately caught my attention. Rather than hijack that thread though I'm starting a separate one (ain't I sweet? :o ).

I have been looking for a pure glider to use for windier conditions and perhaps sloping. I decided a flying wing would be the best choice and I want to build it as a woody (no offense, but ARF's and foam just don't do it for me). The fact that this is not only a built up wing, but a fore-swept wing - a'la Bird of Prey - makes it all that much more titillating. :D

My question is does anybody here know anything about this bird? How difficult is it to build? To fly? I will be using balsa, it will be RC and what I'm interested in is casual flight, no DS'ing or aerodynamcs. Any info, leads to build instructions or tips y'all could give are appreciated.

TIA :popcorn:

#2 Jon Snow Nov 13, 2012 03:37 PM

I remember that got a lot of comment when it was posted.The design has certainly stood the test of time.
Mark(Quick61) was interested at the time,he may have a bit more info.
Stuart

#3 Quick61 Nov 13, 2012 05:35 PM

Yea, I really like that one. If your going to do an RC conversion (and why would you not?) I would upgrade the main spar 1/4x1/8 with I beam shear webbing and more than likely go for a rudder elevator set up than elevons on this one, but maybe it's just me. As far as to how hard it would be to build? Asking that kind of hints that you have not built a bunch of scratch woodies. :) Though, with a little thought and taking your time it should not be that hard a project to take on. At least they are calling for balsa formers and not ply. Those formers made of ply would almost be a pain to cut by hand.

I'd say GO FOR IT!!! Start the build, and if you get real stuck on something, snap a few pics and ask. Lot's of good folks here and at least one or two of them might even have a clue. :rolleyes:

I really don't know of any real build instructions as such out there but it should be more or less straight forward and build up like most any other. nothing all that special going on in the plans that I can see. Well, other than the funky way they want the wings attached. Might be the other thing to mod... Music wire and brass tubes might be a better way to stick the wings on.

Mark

Mark

#4 Jon Snow Nov 14, 2012 05:42 AM

Just been having a look at the drawing.Leading edge wingtips are interesting.Also shows 1/8" washout?
Stuart

#5 Quick61 Nov 14, 2012 10:39 AM

Quote:

Originally Posted by Stupot46 (Post 23264863)
Just been having a look at the drawing.Leading edge wingtips are interesting.Also shows 1/8" washout?
Stuart

I really think that "washout" should be "washin" as it is a forward swept wing. good catch there Stuart, I forgot to mention that. EDIT--- If your read what was here before, forget it. I looked at the plans further and those LE wingtips do look interesting. Now i am wondering if they really do mean washout. That slat is like what is used on the STOL aircraft.
Mark

#6 Jon Snow Nov 14, 2012 05:05 PM

Quote:

Originally Posted by Quick61 (Post 23266507)
I really think that "washout" should be "washin" as it is a forward swept wing. good catch there Stuart, I forgot to mention that. EDIT--- If your read what was here before, forget it. I looked at the plans further and those LE wingtips do look interesting. Now i am wondering if they really do mean washout. That slat is like what is used on the STOL aircraft.
Mark

I've just posted a Q about them on the free flight forum,see if they can shed any light.
Also what's with the hook? Just to protect the slat?
Stuart

#7 Quick61 Nov 14, 2012 05:13 PM

Quote:

Originally Posted by Stupot46 (Post 23269650)
I've just posted a Q about them on the free flight forum,see if they can shed any light.
Also what's with the hook? Just to protect the slat?
Stuart

To my mind, it would seem to be a part (being out on the tip of the LE) would be much better off bending on a tip strike than being balsa and breaking. That's the way i am seeing it.

Mark

#8 BMatthews Nov 15, 2012 10:37 AM

On the control surfaces.

There's nothing wrong with using ailerons but because of the sweep you'll want to use separate inboard elevators and outboard ailerons instead of mixed elevons. The reason being you want the elevator function at the rear most point of the wing and the aileron function at the most outboard. On a swept BACK flying wing these two points happen to both be at the tips of the wing so elevons work. On a swept forward wing these two points are not at the same spot. Hence the separation of the controls.

And no offense intended to the guy that did the plans but the fin on the plans simply does not match the picture. The fin in the picture has a far more elegant look.

Achieving a stable design in this case will be a fun challenge. Either there needs to be a trifle of washIN on the tips or the center area elevators will need some up trim.

A cheap and dirty small scale chuck glider with flat wings will soon answer a few questions on how best to trim the model. Try some elevator to see if it can be stabilized. Then try another with some washin on the tips and see how it works out for stall response.

The only thing with a washin trim is that it reverses when inverted. So just adding some center section reflex with a bit of elevator trim would seem to be the better option so it can just as easily be switched to the proper position when inverted with a bit of forward stick pressure.

#9 Fly Wheel Nov 17, 2012 10:28 AM

Quote:

Originally Posted by Quick61 (Post 23261175)
Yea, I really like that one. If your going to do an RC conversion (and why would you not?) I would upgrade the main spar 1/4x1/8 with I beam shear webbing and more than likely go for a rudder elevator set up than elevons on this one, but maybe it's just me. As far as to how hard it would be to build? Asking that kind of hints that you have not built a bunch of scratch woodies. :) Though, with a little thought and taking your time it should not be that hard a project to take on. At least they are calling for balsa formers and not ply. Those formers made of ply would almost be a pain to cut by hand.

I'd say GO FOR IT!!! Start the build, and if you get real stuck on something, snap a few pics and ask. Lot's of good folks here and at least one or two of them might even have a clue. :rolleyes:

I really don't know of any real build instructions as such out there but it should be more or less straight forward and build up like most any other. nothing all that special going on in the plans that I can see. Well, other than the funky way they want the wings attached. Might be the other thing to mod... Music wire and brass tubes might be a better way to stick the wings on.

Mark

Mark

This is true. I have yet to build from plans alone, unless you count my Miss Stik which is about as close to a scratch build as a kit can get. :rolleyes: This is another reason I feel a wing would be a good place to start - simplicity, and as it is intended to be a chucker than building a prototype per plans would let me experiment with the design in real world conditions.

As this bird is intended for Windier conditions and slope I can see the sence of a rudder for yaw control; however since the wings do have a slight dihedral (3.375" over span length) how would the rudder affect flight? Edit: I don't plan on areobatics, so how the washout or in applies to inverted flight would be moot.

I have saved the .pdf plans, so I can wait and ponder as long as I like before starting such a prodject


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