Dakota Cub’s Extended Slotted Wing
Flight safety is something all pilots speak about. They live it, accept it, and always hope to choose it in their day-to-day lives in the aviation world. For the Super Cub fanatic, the Extended slot bonus 100 Wing from Dakota Cub offers pilots the opportunity to enhance their safety margin as well as boosting the climb performance of the aircraft.
Imagine flying your Super Cub at a high angle of attack with the airspeed indicator reading 20 mph, then rolling into 60-degrees of bank and initiating a climbing spiral while selecting a power setting that’s less than full throttle! That is the typical exhibition 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, plopping it down, or wing drop on stall.
Mark Erickson, the founder of Dakota Cub, began his mission in the 1990’s. All he wanted was a Cub rib. Nothing from Piper was available at a reasonable cost and since the Piper ribs were so fragile, he decided to build his own. He applied modern-day technology to an old Piper wing that was originally developed for the YL-14 liaison version of the J5C Cub. The YL-14 wing was a slotted wing. According to Erickson, there were only 14 of these aircraft built before the end of World War 2. They were specifically engineered for short take-offs of 100-feet and climbs with high angles of attack. There are only two of these still in the air today – one in Spain; the other in Nebraska.
The Dakota Cub Extended Slotted Wing has several variances when compared to the original Cub wing and the L-14 wing for that matter. Erickson revised the original Piper US35B airfoil used for the L-14. He developed a custom “T” shaped extrusion with the same dimensions that when used in building a truss-style rib, is lighter, simpler to work with, and more robust than the original wing. Erickson obtained a STC for the new wing in 1993.
Erickson’s new rib only adds seven lbs to the weight of each original Piper wing. The new wing has been structurally tested to in access of 2,200 lbs, however, the STC limits the gross weight to 1,750 lbs for the original wing or 2,000 lbs for those wings equipped with the Wipaire One Ton Cub STC. This artificial reduction will hopefully be changed in the future. In the intervening years, Erickson has designed ribs and many other parts that are FAA PMA-ed for all rag-wing Pipers. Erickson was granted the STC for the full-length leading edge slot in 1998. This slot helps preserve the boundary layer of airflow at slow speeds. On top of that, Erickson engineered a squared off wing and got rid of the tip bow giving the wing an additional 6% surface area, increased the flaps which results in 44% more flap area, and pushed the ailerons outward 23-inches to the edge of the wing. He calls it the “Extended Wing.” The squared wing adds about 8 lbs to the original Piper wing.
Adding a slot to the Extended Wing adds another nine lbs per wing, but the increased safety envelope from which to fly is well worth the trade-off. The flight characteristics of the squared-off and slotted wing, which Erickson calls the “Extended Slotted Wing”, is the primary advantage and emphasis with regard to choice of wings to include in your Cub project. The Extended Slotted Wing is the best performing wing offered by Dakota Cub. It has a 135-inch slot, a squared-off wing with 102-inch ailerons, and a 90.25-inch flap. Dakota Cub also offers the standard Cub wing and a squared-off wing without the slot.
The Extended Slotted Wing is simply a safer wing. It permits a higher critical angle of attack, slower stall speed, and practically eliminates the sudden loss of lift as opposed to a straight wing. It delays the separation of the air flow from the wing surface, thus aileron authority is maintained and in many cases the only sign of a stall will be a higher-than-normal rate of decent. This phenomenon allows the sink rate of the aircraft on approach to landing to be controlled by power alone enabling a more precise touchdown point without fear of a wing stalling or falling off on one side. The wing also has an improved roll rate due to the ailerons being extended to the end of the wing.
If you want to take full advantage of the Extended Slotted Wing on your Super Cub, then it is recommended to install a 3-inch gear extension. The gear extension will allow the slow speed capabilities of the wing to take full effect upon landing. Larger tires will provide for this as well. Short gear coupled with small tires will result in tail wheel first landings and a take-off run that is longer than optimal because it’s 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 sink control, slower landings, and a much greater margin of safety. A wide-body fuselage from Airframes, Inc features an extended fuselage, and when combined with the larger control surfaces and the slot, a pilot can fly at a 45-degree nose-up attitude, land at 25 knots, and still have a wing that hangs in the air.