Airpower Magazine, Volume 7 No. 3 May, 1977
Custer soon came upon a distinction that has eluded other inventors, postulating that when air passes over an object, as in the barn roof incident, that is "speed of air". However, when an aircraft flies through the air, that is "air speed".
Now don't just put this off as semantics, not just yet, anyway. It is Custer's theory, and it is best to use his words to describe it, i.e., "it is the speed of the air and not the speed of the object which counts. The airfoil was designed to obtain a reaction from the air mass through which it is moved. The [channel wing] was designed to obtain a reaction from the air mass moved through it."
In essence, Custer says that in his wing, the movement of air through the channels reduces air pressure in those channels, and that atmospheric pressure on the bottom of the channel airfoil then creates lift in direct proportion to the pressure reduction in pounds per square foot.
Other engineers have said it better for Custer, but his comments are essentially correct. In stricter terms, an engineer might say the following: "Greater lift coefficients are obtained by the effect of the propeller slipstream deflecting the air mass through which the wings are moved, by suppression of the boundary layer with high velocity slipstream, allowing the wing to fly at higher angles of attack before stalling, and by the vertical lift component due to the inclination of propeller thrust at high angles of attack."
I like Custer's way better.
Speaking again in more practical terms, the pusher propeller, tailored closely to almost touch the lip of the channel (Custer has experienced "channel shaving" in some of his experimental propellers) sucks air through the big half-tubes, and the Bernoulli principle does the rest. The propeller/channel juncture is critical, and some of the most efficient results have been obtained when the juncture was temporarily sealed by pouring water into the channel.
All of the above might sound like double talk, if Custer had not demonstrated his principle in several models and four full size aircraft, or if extensive testing had unquestionably refuted his claims. continue...