# "SkyWing" hybrid wing body ultralight

### Help Support HomeBuiltAirplanes.com:

#### Allen

##### Well-Known Member
He doesn't care if it supports his weight safely without buckling. He cares if it's cheeeep.

The cost of the pilot is no concern here.

May I suggest the Bachem BA-349 and Yokosuka MXY-7 as relevant case studies here?
I wish you would not waste everybody's time with your witty Don Rickles wannabe comments. We have lives with lots of other stuff to do. Thankkkkks for understanding

#### Aerowerx

##### Well-Known Member
Hmmm, You see the 'U' connector with serifs? That is the shape of most rural highway speed limit sign poles....
You mean the ones made of steel???

#### WonderousMountain

##### Well-Known Member
Take 1 mm of E-glass, 10cm, your buckling resistance will be 1/10^2 1 mm spanning 1 cm. More legibly 1%, supposing you calculate 10x weight factor, an off axis load would only need to be about 6 degrees assymetric. Do a 1/4 inch foam or light wood core, and you might hold together. It wouldbe safer if it broke on the ground. & BTW, I do like it, listen to the elders.

#### Victor Bravo

##### Well-Known Member
HBA Supporter
I wish you would not waste everybody's time with your witty Don Rickles wannabe comments. We have lives with lots of other stuff to do. Thankkkkks for understanding
Wish granted.

Please accept my apology for wasting everybody's time, while you regale the same group with such feasible and viable ideas.

#### poormansairforce

##### Well-Known Member
As shown below, I don't want to angle-cut the board edges where they fit together at angles. Tooo dicey. I prefer to retain the perfect factory edges and make the angle with wet fiberglass cloth. Comments?
It doesn't take much to hot wire those angles and use my method to glue them together. The resulting joint with some fiberglass would be much stiffer and lighter than what you are proposing.

You are slowly "rediscovering" why composites (foam/fiberglass) are built the way they are....keep going.

Last edited:

#### Aesquire

##### Well-Known Member
The MXY-7 is a well proven design, while the Bachem failed at flight test and never accompanied anything it was intended to.

Also the mission profile, naval attack & interceptor, were radically different.
Not that I'm volunteering to test pilot a reproduction of either.

#### Allen

##### Well-Known Member
Here's a preliminary concept of the SkySled design.
Think monocoque 2" foam skin.
Think sled kite, think Facetmobile without the complicated tube frame. ;=]
My beloved cheeeep PVC spars have been replaced by top to bottom foam partitions. Sniff. They use reinforced finger joints where they cross.
It features quick and EZ construction costing less than $5,000 to first flight. 8=0 Impossible. Not. All a builder-would-be-pilot needs, is a straightedge, a hot knife, some fiberglass and lotsa pots of epoxy. [no tubes nor rivets nor welders needed] I am concerned about drumhead effect on the largish 4' X 7' wing panels. Drumming can be eliminated by gluing foamy X's across the interiors of the skins. This resembles the old Horton "wingless" planes. That's a bad adjective, the plane IS a wing, a section of one anyway. The best description is to call it a "flying wing with short wingspan." Think up and you'll go up if you don't blow up. AM This 3D drawing erroneously makes it looks like the wings are longer than they are wide. Not true. The aspect ratio of span to chord is 1:1. It is a square airplane. See an article on the "Skyjacker" original version at page 82 at https://books.google.dm/books?id=tQAAAAAAMBAJ&lpg=PP1&pg=PP1#v=onepage&q&f=false #### Attachments • 106.4 KB Views: 33 • 83.6 KB Views: 32 Last edited: #### Allen ##### Well-Known Member What would be the arguments for and against standard fabric covering versus thin fiberglass cloth for covering this monocoque foam wing-body SkySled? #### Allen ##### Well-Known Member Also for discussion.... can I omit some of the 4X7' foam skin panels and instead use fabric skin between the wide spacing of the spars? It seems that normal fabric wings want ribs every foot or two. But how necessary IS that if ur only going 30 knots? [Maybe just put some foam strips across the openings to stop the drumming?] #### Allen ##### Well-Known Member SkySled cutaway view of the 'egg crate' frame upon which the Styrofoam brand monocoque skin can be mounted. The inner two ribs will be trimmed to follow the airfoil shape. The outer rib wingtips will remain the same shape and will include rudders. Ribs will get lightening holes cut in them. "Facets don't cause much drag," said Barnaby Wainfan. So i wont fair the wing cover seams much. The leading edge will be radiused a fair bit to give better stall characteristics. Thanks to Barnie's airfoil manual. Everybody GET one. '=] I'm now making a rough preliminary 1/4 scale mockup foamy to see how it feels. Full size will be: 16 Long X 16 Wide X 3' High Very lowwww aspect ratio ;=] Keep lookin up and you'll GO up. P.s. Second Life virtual world's website has a pretty good 3D editor. Fairly user-friendly. Last edited: #### Allen ##### Well-Known Member Simplified even more.... #### Attachments • 316.9 KB Views: 30 • 111.7 KB Views: 31 #### Aesquire ##### Well-Known Member You can make most of that just out of fabric. I have an important question. How will you make it pitch stable? it appears, to my eye, to "want to" pitch nose down. A cambered shape like shown has a lot of nose down pitch moment. The Skyjacker has a close coupled tail, to balance that force. Paragliders, all fabric and "strings" ( high tech synthetics like Kevlar ) have pendulum effect that provides a measure of pitch stability by a gravity powered soft lever arm. Their wings would just flip back over front, otherwise. Some use a reflexed airfoil that has less pitching moment, just as most rigid flying wings do. Your design doesn't have almost all the mass hanging on a long lever, like a parachute, and I don't see any stabilizing tail or reflexed area. Basic cartoon science Pitch Stability 101. imagine a see-saw/teeter totter. The center of lift of the wing is the pivot point in the middle. On most aircraft the center of gravity is in front of that pivot, pulling the nose down. The tail, or reflexed trailing edge, is behind the pivot, pulling down to counteract the nose down pull. The pilot varies the down force on the tail to control the pitch, or nose angle up & down. here is the IMPORTANT part. The weight pulling the nose down doesn't change with airspeed. The force pulling The tail down increases with airspeed. Thus, as the plane speeds up, the tail forces the nose up, slowing the plane. As the plane slows down, the tail force diminishes, allowing the nose to drop, making the plane speed up. So all the forces balance, literally and figuratively, to make a plane stable. Now, there are exceptions that do the balancing act a bit different, like canards and tandem wings, but they still need to arrange the weight, lift, and variable pitch forces to be stable. ( Feel free to clarify my uber-primitive version and correct errors ) #### Aerowerx ##### Well-Known Member If you look carefully at the Popular Science cover in post #147, there appears to be some reflex by use of the elevons. That is typically how it is done on unswept tailless aircraft. A swept wing tailless is a bit more complicated as part of the wing pitching moment is behind the neutral point. #### Allen ##### Well-Known Member You can make most of that just out of fabric. I have an important question. How will you make it pitch stable? it appears, to my eye, to "want to" pitch nose down. A cambered shape like shown has a lot of nose down pitch moment. The Skyjacker has a close coupled tail, to balance that force. Paragliders, all fabric and "strings" ( high tech synthetics like Kevlar ) have pendulum effect that provides a measure of pitch stability by a gravity powered soft lever arm. Their wings would just flip back over front, otherwise. Some use a reflexed airfoil that has less pitching moment, just as most rigid flying wings do. Your design doesn't have almost all the mass hanging on a long lever, like a parachute, and I don't see any stabilizing tail or reflexed area. Basic cartoon science Pitch Stability 101. imagine a see-saw/teeter totter. The center of lift of the wing is the pivot point in the middle. On most aircraft the center of gravity is in front of that pivot, pulling the nose down. The tail, or reflexed trailing edge, is behind the pivot, pulling down to counteract the nose down pull. The pilot varies the down force on the tail to control the pitch, or nose angle up & down. here is the IMPORTANT part. The weight pulling the nose down doesn't change with airspeed. The force pulling The tail down increases with airspeed. Thus, as the plane speeds up, the tail forces the nose up, slowing the plane. As the plane slows down, the tail force diminishes, allowing the nose to drop, making the plane speed up. So all the forces balance, literally and figuratively, to make a plane stable. Now, there are exceptions that do the balancing act a bit different, like canards and tandem wings, but they still need to arrange the weight, lift, and variable pitch forces to be stable. ( Feel free to clarify my uber-primitive version and correct errors ) How bout simply moving the pilot seat forward? Would that be a good remedy for the pitch-up moment?? #### Allen ##### Well-Known Member SkySled rough mockup quarter scale model is started. Using 1" thick Owens-Corning pink XPS foam because its all i can get locally. 2X2' sheets are$5.50 and itll need abt ten sheets.

Its good for practice using the materials on a mockup. I am impressed with the 3" Tyvek tape and will experiment with it to see how it works for full scale "lifting wing-bodies. That's the best description for the old term, "wingless" aircraft. It has a section of a wing so is not wingless. ;-]

#### Aerowerx

##### Well-Known Member
How bout simply moving the pilot seat forward? Would that be a good remedy for the pitch-up moment??
Why don't you get yourself a copy of XFLR5 and learn to use it. Keeping in mind that it is a simulation, it can help you answer questions like this.

Besides pitching moments you have to also consider stability and control sensitivity. This can be hard to do without the tail surfaces on a long moment arm.

#### Tiger Tim

##### Well-Known Member
Allen, that’s an interesting project you have going there. Is your scale mock-up going to fly? I hope so, as I think there’s a lot to be learned from it especially when you’ve come up with such an original design. When you do fly it please fly it lots in many different weight configurations and test maneuvers. I’d suggest going so far as duplIcating a full-scale airplane’s lengthy test program and modifying the model accordingly as you learn its quirks.

Elsewhere on the forum are two rather lengthy threads about a prototype that had a quarter scale model built but not tested beyond showing it would lift off the ground before starting work on the real thing. Flight testing the real thing has shown time and again that maybe the model should have been fully tested before locking in the design. I can’t stress enough how important it is to learn from that.

#### Rhino

##### Well-Known Member

I wish you would not waste everybody's time with your witty Don Rickles wannabe comments. We have lives with lots of other stuff to do. Thankkkkks for understanding
Yes, maybe he's being a bit too sarcastic, but he's also trying to keep you from killing or severely injuring yourself. With the amount of time that airplanes, PVC and polystyrene have been around, at least acknowledge that other people have tried what you're doing and learned valuable lessons from it, and that some people here may be knowledgeable in that area.

And yeah, it was a little funny. [off-topic]That was my favorite scene from that movie.[/off-topic].

#### Aesquire

##### Well-Known Member
How bout simply moving the pilot seat forward? Would that be a good remedy for the pitch-up moment??
Unfortunately, no, and the problem with almost all shapes like a "traditional" airfoil is that the camber, the curve, pitches the nose down , and increases with speed.

Here is an example of a wing/body design that's only flown a few feet up.

Notice the big horizontal tail that keeps it from flipping nose down into the drink after it lifts off. You probably don't need one that big or position, but most flying machines have a balancing surface that changes how much it pushes with airspeed.

It can be weird with flying wings and lifting body designs. A typical modern flex wing hang glider doesn't have a separate tail, but still does the airspeed changing balancing act with sweep and twist.
Notice that the wing at the center is at a higher angle to the air than the wing tips. Those tips don't actually push down in normal flight ( but will push the back down & nose up in certain situations like a past vertical dive ) instead the lift vector, the direction the wing lifts, changes from center to tip in a curve that gives the same pitch stability as a tail on a 747. It's subtle, very not obvious how it works, I'd need drawings and hand gestures...

#### Aesquire

##### Well-Known Member
I find simple free flight models, paper airplanes too, can teach a lot about how a design flys.

Forget the stupid darts ( "regular paper planes" ) and go straight to the best one ever.
Build the Barnaby Paper Aeroplane

Back in college I had a reputation with these, I would stand and talk with someone and repeatedly toss it in a circle around them and back to my hand. By varying the angles you fold down the tail fins you change how stable it is. I highly recommend Captain Barnaby's book for both paper planes and the simple way he explains aerodynamics. https://howardfink.com/?p=66