Flight safety is something all pilots talk about. They live it, accept it and hope to always choose it in their day-to-day in the world of aviation. For the Super Cub fan, the Dakota Cub’s extended slotted wing offers pilots the opportunity to improve their margin of safety as well as increase the aircraft’s climb performance.
Imagine flying your Super Cub at a high angle of attack with the airspeed indicator indicating 20 mph, then rolling into a 60 degree bank and starting an upward spiral while selecting a power setting that is less than full throttle! That’s the typical exhibit that sells the Dakota Cub Extended Slotted Wing. The second most talked about quality of this wing is the ability to have full flight control authority at high angles of attack. No more soft controls, dropping it, or dropping the wing at the stall.
Mark Erickson, the founder of Dakota Cub, began his mission in the 1990s. All he wanted was a Cub rib. Nothing from Piper was available at a reasonable cost and since Piper’s ribs were so brittle, he decided to build his own. He applied modern technology to an old Piper wing that was originally developed for the YL-14 linkage version of the J5C Cub. The YL-14 wing was a slotted wing. According to Erickson, only 14 of these aircraft were built before the end of World War II. They were specifically designed for short 100-foot takeoffs and high angle-of-attack climbs. There are only two of these still on the air today: one in Spain; the other in Nebraska.
The Dakota Cub extended slotted wing has several variations compared to the original Cub wing and the L-14 wing. Erickson revised the original Piper US35B airfoil used for the L-14. He developed a custom âTâ shaped extrusion with the same dimensions that, when used to build a beam-style rib, is lighter, easier to work with and more robust than the original flange. Erickson obtained an STC for the new wing in 1993.
Erickson’s new rib only adds seven pounds to the weight of each original Piper wing. The new wing was structurally tested for 2,200lb access, however the STC limits the gross weight to 1,750lb for the original wing or 2,000lb for those wings equipped with the Wipaire One Ton Cub STC. It is to be hoped that this artificial reduction will be changed in the future. In the intervening years, Erickson has designed ribs and many other parts that are FAA PMA approved for all Rag Wing Pipers. Erickson received the STC for the full-length leading edge slot in 1998. This slot helps preserve the boundary layer of airflow at low speeds. On top of that, Erickson designed a square wing and removed the bow from the tip, giving the wing an additional 6% surface area, increased flaps, resulting in 44% more flap area, and pushed the ailerons out 23 inches toward the edge of the wing. He calls it the “extended wing.” The square wing adds about 8 pounds to the stock Piper wing.
Adding a slot to the extended wing adds another nine pounds per wing, but the increased safety envelope to fly from is well worth it. The flight characteristics of the square and slotted wing, which Erickson calls “Extended Slotted Wing”, is the main advantage and emphasis regarding the choice of wings to include in his Cub project. The Extended Slotted Wing is the best performing wing the Dakota Cub has to offer. It has a 135-inch slot, a square wing with 102-inch ailerons, and a 90.25-inch flap. Dakota Cub also offers the standard Cub brim and a square brim without the slot.
The extended slotted wing is simply a safer wing. It allows for a higher critical angle of attack, slower stall speed, and virtually eliminates sudden loss of lift compared to a straight wing. It delays airflow separation from the wing surface, so aileron authority is maintained, and in many cases the only sign of a stall will be a higher than normal rate of descent. This phenomenon allows the rate of descent of the aircraft on approach to landing to be controlled by power alone, allowing for a more precise touchdown point without fear of a wing stalling or falling off the side. The wing also has an improved roll rate due to the ailerons extending all the way to the end of the wing.
If you want to take full advantage of the extended slotted wing on your Super Cub, installing a 3-inch gear extension is recommended. The gear extension will allow the wing’s low speed capabilities to take full effect upon landing. The larger tires will also take care of this. A short gear coupled with small tires will result in first tailwheel landings and a longer than optimal takeoff run because it is more difficult to achieve that higher angle of attack.
The end result of all this innovation is a Cub that has better climb performance, better descent control, slower landings, and a much higher margin of safety. A widebody airframe from Airframes, Inc features an extended fuselage, and when combined with the larger control surfaces and slot, a pilot can fly with a 45 degree nose up attitude, land at 25 knots and still have a wing hanging in the air.