Arc Wing Versus Planar Wing

In the June 2008 edition of Flying Magazine, noted aviation expert and writer Peter Garrison writes about the forces associated with airplane lift in a very interesting article titled "The Bernouilli Brigade". He discusses at length why the lift possible from a wing is less than one would think. Here is some of what he says:

"The pressure difference between upper and lower surfaces causes spillage at the tips - this is the reason for the tip vortex - and robs the wing of 5 to 10 percent of its theoretical lift. Another loss occurs at the center of the wing where the fuselage interrupts air flow. The imaginary portion of the wing that lies within the - reported wing area includes this hidden part - produces in reality, no lift. But changes in the pressure are gradual, not instantaneous, and so the effect of the fuselage is to produce a dip rather than a sharp-edged gap in the spanwise distribution of lift. Depending on the fraction of the wing that lies within the fuselage, another 10 or 15 percent of potential lift may be lost here."

He also refers to the losses from the tips of the non-spanwise flaps.

His article deals with the loss of lift of the straight or planar wing. At Aeromobile Inc., we think our arc wing obviates several of these losses. In my previous blog entry, called "A Wing that Really Lifts", I list all the reasons the arc wing has superior lift to the planar wing. Here I will just mention a few:

1. The arc wing has inherent "winglets" and minimal tip vortices to reduce that 5 to 10 percent of lift of the straight wing.
2. There is no fuselage interrupting the arc wing span. The fuselage is under the arc wing saving a additional 10 or 15 percent of wing lift.
3. Taken together, the theoretical saving of the arc wing over the straight wing without the fuselage interrupting may be as much as 10 to 25 percent.

A Wing That Really Lifts

I've talked about the Arc Wing VTOL airplane in a number of earlier posts. Today, I want to talk mostly just about the arc wing itself. No airplane today has a wing like it, and I feel it would have many advantages even for conventional take off and landing (CTOL) aircraft, as well as vertical take off and landing (VTOL) aircraft.

This photo shows just the shape of the arc wing:

And, this image shows the arc wing in combination with a dual rotating propeller and a flap at the back that would be used for VTOL operations:

What are its advantages of the arc wing? When combined with dual rotating propellers:

1. The arc wing has inherent "winglets" and minimal tip vortices to reduce 5 to 10 percent of lift of the straight wing.
2. There is no fuselage interrupting the arc wingspan. The fuselage is under the arc wing saving an additional 10 or 15 percent of wing lift.
3. Taken together, the theoretical saving of the arc wing over the straight wing without the fuselage interrupting may be as much as 10 to 25 percent.
4. The arc wing has greater lift, (L/D), for a given span than a straight wing.
5. An airplane designed with the arc wing will have as shorter span for a given load factor.
6. The arc wing stalls at 33 degrees angle of attack vs. the straight wing that stalls at 17 degrees, resulting in later stall and higher lift.
7. Arc wing flaps are full span and without tip losses, inboard or outboard.
   The arc wing has positive pitch stability that removes the need for a horizontal empennage and the structural weight and drag thereof.
8. The arc wing can assume any angle of attack and "freeze" at any angle of attack by moving the tip mounts fore and aft. We have a video that my son William D. Bertelsen narrates that shows the arc wing stability at any attack angle.