If you have a wooden model of a plane, I would not advise to rip off the tail. If you throw the model without tail, it will dive to the ground. Why? Every airfoil has three forces. Lift,weight (both vertical) and drag (horizontal). If lift and weight are placed on the same spot, the airfoil is stable. But most airfoil are not stable. The liftforce is mostly located after the weightforce. So it generates a turningmoment. This turningmoment is compensated with the downpushing force of the horizontal tailsurfaces.

swepted wings

Unswepted wings

Tail on tips

Low CG

Flying wings, why?

The name flying wing is not totally correct. Most full-scale design still have some sort of fuselage. The Horten-brothers and Northrop made (to my idea) the only pure flying wings. The Horten IX V2 (1945) and the B-2 (1990’s) have proven that the concept can be achieved. Other designs have fuselages and fall under the name "tailless airplanes". But some still have vertical tailsurfaces. So… we make it ourself simple and call them all "flying wings".

Swepted flying wings

What is achieved by using sweep and twist? Well, the tips provide the compensating down-(in case of backward sweep)force or up-(in case of forward sweep)force to the turningmoment of the airfoil in the center.

The angle of sweep can be shown in two ways. One is to the leading edge (used by Horten), the other is to a line which is placed on 1/4 of the wing. Make sure, when using data of excisting models, that you don't use the wrong angle. If not mentioned which angle they use, take the one to the 1/4-line.

The twist-angle is the angle between the airfoil at the root of the wing (nearest to the fuselage) and the airfoil at the tip of the wing.

1. If you are planning to make a model, be prepared to see some complicated formulas in your research. But don’t let it scare you. A friend of me made some good models, just be guessing the angles or using data from full-size airplanes. I have seen a site that gives a good help in choosing the right angle of sweep and twist. Just read a bit of the given theory and use the curves to determine the angles. Site.
2. Due to the sweep is construction more difficult than the flying wings with autostable airfoils, which mostly have no sweep.

General Aircraft GAL 56 (third version)
A lesser known English flying wing which had a 36,4 degree sweep.

The Utopia, a modern competition hangglider.
Made by BrightStar Gliders and flown here by Brian Porter,
a many times champion in the hanggliding competition.
You can clearly see the sweep and the controlsurfaces.
I got the picture from Brian Porter.
Click the picture to get a even larger size (JPG, 636 kB).

(also called unswepted flying wings)

These designs use an airfoil which doesn’t require a sweep. Therefore they are the most compact version of a flying wing. Fauvel, a french designer, became famous with his unswepted designs. These designs are without vertical tail very unstable, so most designs have a vertical tail.

This airfoil (CJ-5) is an example of an autostable or reflexed airfoil. Note that the trailing edge goes up. You can see a reflexed airfoil as a normal airfoil with a tail-airfoil in one.

The Debreyer Pelican, a compact ultralight, uses the 17% thick Fauvel reflexed airfoil.
"Ideal for a beginner" as the manufacturor says.
CLick picture to go to a page about this remarkable airplane.

Marske Pioneer, available as kit and on plans (picture given by Buddy and Lloyd Watson)
Click picture for link to site of Marske (www.continuo.com/marske) and also see the Marske Monarch.

1. Less work on basic design. You don't need to calculate twist and sweep.
2. Compact. Since (mostly) no sweep is used, these designs are easy to place in a hangar.
3. No sweep means no difficult main spar connection.
4. Autostable means no stall and no spin. The condition is that the CG (center of gravity) is placed on the right spot.

Disadvantages:

1. Reflexed airfoils have less lift than normal airfoils. So more wingarea is needed to have the same lift.

Tails on tips

This concept is, according to some people, not a true flying wing. Euh... I don't see a classic tail, nor a canard, so I see it as a flying wing.

What has happened in this concept? The wing has a great angle of sweep (a German design had 40°). The classic horinzontal tailsurfaces are placed on the tips of the wing. This way you have the nessasary downforce to compensate the turningmoment of the wing (the force-arm (distance between center of gravity and elevators) is long enough) and you don't need to have a long fuselage to hold the tail. Most known designs have the vertical tail also placed on the tip. Here you can also combine the elevators with the roll-rudders (combination known as elevons).

The German company Blohm & Voss did some tail-on-tip-designs in WW II. The Luft '46-site (see links nurflugel-site) has many of the unfinished projects of the Luftwaffe. They have superb 3D-drawings of some of these designs.

A nice picture of the Blohm & Voss P212-3 made by Tor Pedersen (permission granted by Dan Johnson) Click picture for link to Luft '46 site (www.luft46.com) to see more of the last German designs of WW II.

Click the thumbnails to see the larger pictures.

Q: I don't known them yet. Any reaction is welcome. A: (From Kenneth M. Dorsett (Specialist, LMTAS Aerodynamic Stability & Control)) "I have some experience with such surfaces on high performance tactical aircraft; however, my comments should apply to a low-speed glider as well. Advantage: A large moment arm with respect to the CG make these surfaces ideal lateral-directional controls. A great deal of control power can be generated by a relatively small surface. By staggering the surface aft (like Blohm & Voss did), you can generate a good deal of longitudinal control as well. These surfaces typically remain effective to very high angles of attack (AoA)."

Disadvantages:

Q: I don't known them yet. Any reaction is welcome. A: (From Kenneth M. Dorsett (Specialist, LMTAS Aerodynamic Stability & Control)) "The primary disadvantage comes from structural integration problems. Tip mounted surfaces such as these are hard to keep stiff -- particularly on a thin-winged, high speed aircraft."

The moment created by the wing gets (fully or partially) compensated by the very low CG. This technique is often used with ultralight. Mostly hanggliders (using weightshift as flightcontrol) use this technique to its full use. "Mitchell used this technique for his B-10 flying wing ultralight." This quote from a Air Enthousiast edition probably mentioned that if the cockpit would be higher placed, that the controlsurfaces needed to be larger to control the airplane. The newer U-2 of Mitchell has a higher placed cockpit, but it also has a longer force arm between the CG and the control areas (the B-10 has a straight wing, while the U-2 has some backsweep). Both airplanes use the low CG technique partially. Flight control is done by control areas hung under the trailing edge of the wing.

Advantages:

1. Very easy in design. No fuss with twist and sweep.
2. You still can use airfoil with some pitchingmoment C_m like a "normal" airplane (not a flying wing). This way lift is larger than the autostable airfoils used in unswepted designs.

Disadvantages:

1. You have not the opportunity to place pilot or engine or equipment in the wing. You can not make profit from the available space in the wing.
2. A cockpit hanging under the wing makes more drag then a integrated cockpit in the wing. Probably the reason why Mitchell made his second design, the U-2, have a integrated cockpit.