Sunbird Build

[erich]

Well.....have decided to take a shot at a plane called Sunbird. It's a flying wing with elevons. Uses a relexed, flat bottomed, turbulated airfoil. Sounds impressive. I assure you of my, mostly vague, understanding of them. Have decided on this plane, because it should build fast, uses only 2 servos, and I have never built a flying wing before. It will be all scratch built. Nuts..gotta make all those ribs, but 1 day of rib making should get it done. Got the plans from RCM a few months ago, along with 2 other flying wings. Chose this one cause it looks to be a fairly straight forward build.

Here are the stats, taken from the small instruction sheet which accompanied the plans.

Designed by: Mike Hollison. Span: 78". Chord (avg.): 10". Area: 780 sq.in.
Airfoil: Reflex. Planform: Double taper.
Dihedral: 1" ea. tip. Length: 23" Ht: 8"
Channels: 2. Controls: elevons.
Flying Wt: 32 oz. Wing Load: 5.9 oz

Have made duplicates of plan, so am using original as templates for ribs and formers. Have cut out all paper ribs and formers. Cut to outside of lines on plans.

erich

[malachite]

You gonna use a radio with elevon mixing or make a mechanical mixer for this one?

Michael...........

[erich]

Would be easier to do a mechanical mix (for me anyway, have not made my peace with computer radios), than a radio mix. But since I need to learn the computer radios, will do an electronic mix.

erich

[Ollie]

See:
RCSD, May 2006 and download it.
http://www.rcsoaringdigest.com/

Read about "Evan Shaw writes about how he designed, built, and flew a radio controlled bird - a full size model of a South African Black Eagle."

And
http://www.rcstore.com/rs/general/listproducts5.asp?catid=32&catego=PL
"Designed by Bob Hoey, this bird-like RC Turkey Vulture uses highly effective wingtip aileron feathers to bank and turn the model just like a real bird. The model has no vertical fin or rudder but is very stable in flight. Built of balsa and plywood, the model is covered with MonoKote and has a drop-away dorsal fin for bungee high-start launches. It can also be dropped from another airplane. The wing is highly under-cambered and slightly reflexed. The plan shows the articulated wingtip aileron feathers in detail.WS: 64 in.; L: 25.5 in.; radio: 2-channel; 1 sheet; LD 2."

And
http://www.angelfire.com/ok5/soar/gpic/eagle.htm

And
Bob Hoey worked with Paul McCready from AeroVironment.

[erich]

Thanks for the link. Ollie.

Just a guess, but seems like it's, the wings reflex, that keeps these kinds of planes and or birds, somewhat stable. Can't wait to see how it works. Will probably have this thing done in less than 2 weeks, maybe even a week. It's going together pretty fast.


erich

[oracle_9]

Is it possible to provide a photo of some sorts of how the sunbird looks like? I googled it in and all I am getting is skybenches HLG sunbird.

Hehe, I am also subscribing to this build thread as well while I am at this. :)

[erich]

Here's the photo on cover of the instructions. Will post pics of plans later. As I said got the plans from RCM.

erich

[cynjon]

Looks like a Birdworks Zipper...is it going to have a towhook or is it just a sloper?

[erich]

It's actually more of a thermal glider, according to the instruction sheet. So it will have a towhook. But I will definitely be doing some ridge hoping with it.

erich

[erich]

Here are the plans, kinda of a simple looking, flat bottom, generic type airfoil. A, 1 piece wing, no rudder, 2 servos, no joiner, or pivot wires. Then you have the fuselage, there's something about it, that, well.....I like. Just don't ask what. This plane is so simple and straight forward, it's just gotta fly well.

erich

[malachite]

What are the control throws like? Hopfully it's not as twitchy and sensitive as some slope planks that have 3/16" total elev travel and very precise CG locations. I see the CG mark on the plans but was just wondering if it said anything in the instructions about CG range with all that reflex.

Michael...........who killed his balsa plank 15 years ago cuz he figured the CG was close enough

[cynjon]

Those are some LOOOOOONG torque rods...have you considered putting micro servos in the wings, since you're going to be using computer mixing anyhow? Seems like it would be a weight-saver and would give a more slop-free control surface, as well.

[erich]

In the fuselage the servos are an asset, in the wings they're a liablility. Would need even more weight to counterbalance. If I was making this plane for super high speed, the extra slop free operation, would be of use. But am not building for that, so the slight gain would be lost on this plane. For thermalling and moderate sloping, the slight loss due to a little loosness will hardly be noticed. It may even be an advantage. I may even change the electronic mixing to mechanical. If I can find an aileron mixer I use to have. But you certainly are right, the torque rods are loooooong runs.

erich

[bobby legue]

I tried the servo in the wing thing in the Klingberg wing and it killed the roll response . Very draggy and slow compared to my friends stock version. Have to side with Erich on this one as he is right. Erich doesnt your 9c radio have an elevon mix built in it?
Bob

[erich]

Taped the, paper rib templates, using scotch tape, to 1/16" sheet balsa. Cut around outside using sharp razor blade, and steel ruler as guide, on straight sections. Did some sanding on each pair of ribs to smooth out curves and true up straight sections. Took about a day to cut out and finish all ribs. Did the same for ply formers. There are 3 formers, 2-1/8" ply and 1-1/4" ply. Had no 1/4" ply so glued 2-1/8" pieces together to make the 1/4" former. Also made the ply joiner pieces 2-1/8" ones and 1-1/4" one, again gluing 2 to make one. The formers took about 2 hours to cut out drill and sand to a very close final shape. Will finish truing up formers after sides have been cut and formers temporarily fitted to sides.

erich

[erich]

bobby legue

Yes it do. But I have a big problem programming these radios. Where the mechanical mixing is much easier for me. But I will attempt the eclectic mixing (no it's not a typo).

erich

[SoarNeck]

I built something similar from the photos in that article, though I wanted something a tad larger. Worked great:

http://www.geocities.com/sunbirdz/WingPage.html

Never saw a report on how the original flew...good luck, looks great!

[erich]

You had 4 servos, plus spoilers, in there, and still kept the weight to 33 oz. That's great. Looks good too. Is it a flat bottom foil, you used? Is the wing 1 piece or 2?

erich

[oracle_9]

Nice looking plane.

Soarneck, I just clicked on your link. Thats one big sunbird.
New joke?? Ok, A Paragon, A zagi, and a Sunbird go into a bar, and the Zagi tells the paragon, hey......

Hmmm, nevermind, there's too many bar jokes out there as it is already.

[mhodgson]

Looking at the plan, and having built plank type wings myself, I would do two things.
1. Put a rudder on it if you plan to tow it up, makes controling on the line so much easier.

2. Put two servos in the wing for the elevons. Removing all that metal (torque rods) from the rear of the wing can only help the balancing. I would put them in front of the spar siting on a plate screwd in from underneath (as there seems to be no spars running along the bottom). Smack bang on the CG so no balancing issues and use two micros which will have little effect on the roll, in my experience.
With a rudder servo in the fuz and none of those troque rods it should still balance about the same I would think.

[erich]

mhodgson

Thanks for the interest and advice. Please do not take this personally. But am probably going to stick pretty much to the original plans. Only thing is, I might try computer mixing for elevons.

erich

[Whorges]

Erich,
You seem scared of the computer mixing. It's really truely not hard. I think you'll be thrilled with how easy it is. It's a lot easy than building for scratch to be sure :O)!

BTW the Sagitta 600 is coming along like a steady turtle. Wings and tail surfaces are done, well still need some minor sanding and covering... and glue is drying on the first fuse former :O)! The nag can smell the barn and is excited to get home!

Good luck with the wing. Looks cool.

[erich]

Hey you got the hard stuff, done, now for the fun, The Fuselage. Post some pics when you get it covered, or even before it's covered. I can figure the mixing out (with a little head scratching), just don't really enjoy it. Took me 2 days to set up the flaperons on the Challenger. Would rather fiddle with steel rods, brass tubes and pretty much, anything mechanical.

erich

[StevenatorLTFO]

Ace used to make a nice little electronic mixer, that sat in between the receiver and the servos, I used one on a RCM Gremlin flying wing once, was way better then the rube goldberg sliding tray I tried at first.

Steve

[erich]

I once made a sliding tray using piano wire and brass tubes. The movable servo was glued to two brass tubes, which then slid on piano wire, with a little silicone on it. This was for a split rudder air-brake, which was on a canard. Worked a lot smoother than the normal spruce trays. What I might do is use an in-line 3 point pivoting mixer which sits on top of one servo, and is pivoted by another. This was done on the Dodgson planes. Also Graupner use to make one of these simple mixers. I had one but can't seem to locate it. At any rate going to give my 9C a shot at mixing it up.

erich

[bobby legue]

Erich, Im proud that you are willing to give mixing a try! After you get your initial settings as stated on the plans you can fly and make small adjustments as you need. Just dont drive 45 miles and leave your instruction manual at home. I learned the hard way.
Good luck to you,
Bob

[erich]

Used same method on ply sides, taping template to ply. Cut out with scroll saw, as razor blades would have taken, forever. Glued 2 sides together and trimmed to final size with sanding block. Also cut out and glued up the giant tail section. This out of 1/4" balsa.

erich

[oracle_9]

Looking at the plans, will you be adding some rounded cheeks on either sides area where the fuse meets the tail? Like to blend the fuse into the tail near the end in a more aerodynamic fashion. Hmm, come to think it that will add more tail weight.

[erich]

Yes, will be fairing in the tail nicely. Got a feeling this plane will not be tail heavy. In fact it may be nose heavy. What a switch, adding lead to the tail.

erich

[erich]

Glued 2 formers to one side with Titebond. Made sure formers were square to side.

erich

[SoarNeck]

You had 4 servos, plus spoilers, in there, and still kept the weight to 33 oz. That's great. Looks good too. Is it a flat bottom foil, you used? Is the wing 1 piece or 2?

erich

Yep, there's not much to the fuse, and no tail, remember? Also consider that flying wings basically act like convention planes with a wing loading that's something like 30% higher.

I honestly don't remember much about the airfoil...you'd be better off squinting at the photo. Wasn't much differnt from the plan version, except I think I had more of a Philips-style entry. This was 6-7 yrs ago, so I can't be sure.

1 piece wing...BIG wing.

[erich]

Used plans to align both fuselage sides, then glued 2 formers with Titebond to 2nd side. Afterwards propped up front end (there's a 10 deg. bend in fuselage about midpoint) so rear would be flush with table. Then added rear former making sure center line on plans matched center on all 3 formers.

erich

[cynjon]

Any progress erich? It's been awhile since your latest build thread slipped off the first page...hopefully you've been out flying!

[oracle_9]

He is probably flying his other models. They deserve air time too. :)