I then taped the same balsa strips to the outer third of the span, expecting to get more tip stall. The result: I couldn't detect any difference during flight testing. I expected them to act like the stall strips used on some full-scale taper-wing airplanes, causing the inner portion of the wing to stall first, leaving the outer portion of the wing remained unstalled, and keeping the ailerons in business. To crudely test the effect of sharp leading edge, I taped 45 degree triangular strips of balsa to the inner third of the span of one of my own design aerobatic biplanes. Add a strip of balsa to the outside 12-15" of wing LE, near the tip. One can easily do an experiment on thick winged, blunt LE'd aerobats. Radios are just too slow compared with a guy sitting in the cockpit. Also, many times initiation suffers since we just can't get enough throw into ele and rud fast enough in radio controlled aerobatic flying. In fact, blunt wing LE takes so much elevator and rudder to partially stall one panel during a snap roll, thatsnaps are often "buried" which makes recovery very difficult and unpredictable. SRT hit it on the head regards to model aerobatics.
This is why one just can't use full scale data on our models and have it work the same. Just don't let your airspeed get too low during a landing approach.įor our IMAC type Extras, Edges, Caps and Sukois with the low wing loading we have the exact opposite is true. This probably explains the popularity of the so-called ice cream cone sections used on Extras, Edges, and Sukois for all-out aerobatics. The blunt section, with its higher lift and abrupt stall is good for maximum possible lift, clean snap-roll entry, at the cost of tendency to stall and snap-roll. Minimum profile drag was reduced only by a percent or so, and was increased at lift coefficients over 0.2 - definitely a poor trade-off, apart from its friendly stall characteristics.Ī very blunt leading edge with radius of about 5% of chord increased maximum lift coefficient to about 1.5, increased minimum profile drag by about 10%, and produced a far more abrupt stall. Old text "Airplane Design" by Warner shows effect of three different leading edge radii for the NACA 0012 symmetrical section.Ī knife-edged leading edge reduced peak lift coefficient from 1.4 to 1.03, but produced a very gentle stall.