Myron (Dan) Freeman wrote: >> I made a discovery today that many of you may already be aware of. I'm planning on using the AS-5046 airfoil on my new wings (I'm replacing the RAF- 48 airfoil) and I noticed that with an incidence of +1.75 degrees on the root wing airfoil and a washout of 3 degrees on the outer wing panel as per plans that this will cause the wing tips to be in a negitive lift condition (actually pulling down on the wing at high speed), so I'm reducing the washout to 2 degrees which will be about neutral only at high speed and might reduce drag. Just some more food for thought.<<
That airfoil (and many others) is still generating lift even at a chord line incidence of less than zero. The washout of the AS5046 as it relates to the KR was carefully optimized by Mark Lougheed, and peer review at the time (including the airfoil's designer) held that it was certainly close enough for KR work. A recent "Wind Tunnel" article in Kitplanes reminded experimental builders not to reduce washout without serious consideration, as stall characteristics can suffer dramatically compared to the minimal performance increase. Also, if you reduce the washout by 1 degree, you're probably going to go nose up about a half a degree. Personally, if I changed anything it'd be to LOWER the incidence by a half a degree at both root and tip, because I find myself cruising at high altitudes in a nose up condition during most of my cross country flying... Mark Langford, Huntsville, Alabama see KR2S project N56ML at http://home.hiwaay.net/~langford email to N56ML "at" hiwaay.net --------------------------------------------------------------
