Originally Posted by
speedracerntrixie
Should we discuss the advantage to making the LE radius at the root a bit sharper then at the tip? Maybe a bit off topic but maybe not.
Not off topic at all in my opinion. Back in the day (and I do mean way back) we use to use that technique to tame some of the SIG planes to make them more enjoyable to fly. This may be getting into sacred territory bordering on blasphemy but SIG is only 60 miles from my house and I knew most of the people who designed those old SIG kits and they were friends. I don't know any of those people who actually used a known NACA or otherwise designed airfoil. Locally we use to joke and call their airfoils "Zip, French Curve or shoe sole" airfoils. Also referred to as "
Looks
About
Right" or LRB airfoils. The resulting airfoils could have some strange stall characteristics at times. Some of those kits could get "exciting" if one shaped the tip LE too sharp. Some of us often suggested making the tip LE radius more more rounded compared to the root. At minimum, we suggested keeping the LE radius consistent from root to tip and the planes flew much better while still maintaining decent snap and spin characteristics. So Speedracer and Pylonracr, your suggestions have merit based on history.
Now a disclaimer: Nothing wrong with those old SIG kits and they were produced and flown in unknown thousands, maybe even millions? But like most things in our hobby, a bit of understanding goes a long ways and can make the building / flying experience more pleasant.