If you like to test a RC model of a flying wing with extreme sweep, go try the Horten H13B jet (electric ducted fan) of RBC (www.rbckits.com). Here you can see the model made by Erik Van Schaik. Click the picture to get to the RBC site.

Another drawing of Graham Ward.
The Lippisch Li P13.
Both engines would make this airplane uncatchable by enemy-fighters.
But ... it never left the drawingboard.
more detailed info at www.luft46.com 

Designs using auto stable airfoils

(also called unswept 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 unswept 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 auto stable 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 ultra light, uses the 17% thick Fauvel reflexed airfoil.
"Ideal for a beginner" as the manufacturer 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.

Advantages:

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. Auto stable means no stall and no spin. The condition is that the CG (centre of gravity) is placed on the right spot.

Disadvantages:

1. Reflexed airfoils have less lift than normal airfoils. So more wing area 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, or 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 horizontal tail surfaces are placed on the tips of the wing. This way you have the necessary down force to compensate the turning moment 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.

I got these pictures from Bjorn Rabben. They show his model of the Blohm & Voss P212. He did use elevons in the main wing instead of the original rudder configuration.

I received this mail from Antonio Fernández (MEWGULL@terra.es), he seems to have had some problems, but now has a good model: "Have been experimenting with "backyard Nurflugels", small flying wings. I first built a high dihedral, 212-01 model that has the fins over the wing, at two-thirds span. It was horrible! spin both sides, flat spins, the lot! The CG range was almost nil (interestingly you must add the weight in the extreme tail, the exhaust of jet!) and then I made a larger 212-03 that has the double winglet-fin assembly on the tips...Steady as a rock, like an arrow on its trail. The winglets act like this: if raised inner only, like ailerons coupled to rudder, gentle turns. If depressed outer, like normal aileron, but sharp response. The rudder makes pronounced almost flat turns, that if exceeded tend to crab and in the extreme, swings out. But stable flyer when all straight and no spins, good cg range and very responsive, proportional to inputs of command. Used reflex profile and no elevons in wing. I´m building larger one with electric fan unit... "  

I found out that RBC makes a kit to built a Blohm & Voss P212-023 RC model (electric ducted fan). So you can test its behavior yourself. I asked about its building and flying. They reacted:

"The P212 flies super (it is my personal favorite jet). He is controlled by ailevons (ailerons and elevators mixed) and the small tipwings are controlled directly at once too. The steering is direct and very effective, but it has a bit too much stability. In other words ...he wants too turn horizontal (yaw) just like a trainer. Not really something you like in a jet, but not bad.
We used a bit less sweep and dihedral than the original design. Although he can fly slowly, it is hard to judge the landings when the wind is low. Due to its great glide ratio you might overfly the airstrip.
There are fences placed on de wings (look halfway the wing) to keep the airflow healthy. I didn't try the model without the fences because I found flying the TA183 without fences not so good. I just wanted to go for good flight behavior at once."

The Blohm & Voss P212-03 jet with electric ducted fan of RBC kits. Click the picture to get to www.rbckits.com

Advantage of tails on tips:

Q: I don't know 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 makes 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 know 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."  

Low CG

The moment created by the wing gets (fully or partially) compensated by the very low CG. This technique is often used with ultra light. Mostly hang gliders (using weight shift as flight control) use this technique to its full use. "Mitchell used this technique for his B-10 flying wing ultra light." This quote from an Air Enthusiast edition probably mentioned that if the cockpit would be higher placed, that the control surfaces 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 back sweep). 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 twists and sweep.

2. You still can use airfoil with some pitching moment C_m like a "normal" airplane (not a flying wing). This way lift is larger than the auto stable airfoils used in unswept designs.

Disadvantages:

1. You have not the opportunity to place pilot or engine or equipment in the wing. You cannot make profit from the available space in the wing.

2. A cockpit hanging under the wing makes more drag then an integrated cockpit in the wing. Probably the reason why Mitchell made his second design, the U-2, has an integrated cockpit.  

Flying Model Simulator

I have great news for those who want to make their first steps in the virtual air. There is a TOTAL free software which gives you the opportunity to fly a few flying wings. The Me 163, the Horten H IV and the SB13! Go visit the site http://simulator.home.pages.de . It is a easy kind of flight simulator. And the looks are good enough. I likes it. Here are some screenshots of models you can fly using FMS. The yellow one is my own creation. Yep, you can build your own FMS models.

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