Coming soon to a lake near me.
- Jul 27, 2021
- Three miles down Four Mile Lake
Perhaps not, but the aerodynamicists Piper hired when they designed the Super Pawnee (PA-36) agree with you.-Not an aerodynamicist
The Pawnee (PA-25) had the Super Cubs wings, and Piper had a detailed study made of airflow over the wings. Thousands of strings were glued to the surfaces so conventional photographs could be made of the airflow. Squared tips worked best. The study was probably before the advent of the down turned tip. The "experts" empirically quantified that many things perceived to be aerodynamic, like elliptical wings, were not in fact aerodynamic.NX-4L - maybe consider changing the wing tips. The rounded stock tips do look good, but squared (in planform) tips perform a lot better. Shape the tips like the STOL boys have done - either a slight droop tip or even a simple slashed tip (when viewed from the from the front - not just a straight cut-off) helps maintain lift out to the tip whereas the rounded tip sheds airflow.
I actually thought that people recommending "clipped wings" were referring to squaring off the wing tips. I have seen a lot of Cubs, Champs, Chiefs, and wooden winged Luscombes where the tips have been squared off at the last rib. Sometimes the aileron is squared off as well-- or more properly built out to square. I imagine that STOL tips made to fit the PA-18 would fit the J-3 as well.
I conversed with someone who built a WA Sport Trainer and he confirmed their "no accessories" light weight of 684 pounds with stock wheels and an A-65-8 powerplant. Mine won't have an X or an H or tail spring and brace tubes, brakes, or any wheeled gear parts, which will lighten it over 40 pounds.
640 pounds of airplane plus 135 pounds of floats, 340 pounds of people, 80 pounds of gas, and 8 pounds of oil is only 1203 pounds, well under WA's recommended 1250 pounds and Zenair's maximum 1278 pounds.