Mark- Which Cherokee used the 23012?
I've flown several airplanes that use 23012, none of which were threatening. Aren't the flight characteristics of a wing nearly as dependent on aspect ratio, geometric twist, wing loading, high-lift devices, stall strips and planform...to name a few...as the section used? I believe you're correct that the Bonanza used 23012 (for most of the outer portion of the wing)...but I always found them one of the most docile airplanes out there. I can't help thinking that making a "sweet"-flying wing is like baking a really good pastry...it's as much a result of the chef's ability as the vitals used. No? -Lloyd Schultz Mark Langford wrote: > Bob Tallini wrote: > > >>The design I would like to use is the one Roy Marsh developed for the KR2S > prototype. It is a modified NACA 230012. << > > Bob, I just plain wouldn't use a 23012, no matter how modified it was. > Although it was used on everything from Cherokees to Bonanzas, the stall > characteristic is not something you want to intentionally build into any new > aircraft. Visit http://home.hiwaay.net/~langford/23012.gif and notice how > the wing stalls very abruptly. It goes from flying to stalled almost > instantly (the "cliff-like" plot on the left). I believe Roy once told me > he had to land at about 80 mph, and that doesn't surprise me. Why not use > an airfoil that was designed specifically for the KR2S by modern methods > with one of the design goals being a reasonable stall speed and gentle stall > characteristic (gradual). If you haven't seen it, visit > http://www.krnet.org/as504x/ for the details, and check the same curves. > You'll see something a lot more gentle. > > Making the spar thinner will give you problems with gear mounting, wing tank > capacity will be significantly reduced, and you have the strength problem > (weight will go up) that you're now faced with. Yes, Roy did it, but Roy > also sold his plane after a few short years. Ron Lee bought it, flew a few > times, and sold it quickly. Not sure if anybody's flying it now, but I'm > not convinced you really want to replicate that wing. > > Funny thing about that plane is that it's the "poster child" for RR's KR2S > advertisements, although the wing is a completely different animal than the > plans call for. > > If you really want to do this, I've temporarily posted some "shareware" > software that will do that analysis for you at > http://home.hiwaay.net/~langford/spar.zip . Plug in the dimensions and > characteristics for a stock wing, then plug in the dimensions for yours, and > then tweak caps and plywood dimensions until you get strength numbers the > same or better than stock. This is just an approximation, as there are fine > points of plywood layers and such that probably enter into it, but it's a > good "ballpark" method of making sure you don't do anything stupid. > > Still, I wouldn't touch that airfoil with a ten foot pole. You mention this > airfoil to an aerodynamicist, and he'll start shaking his head. Yes, I know > Roy's son is an aero engineer, and he specified this airfoil, but he didn't > have the AS504x airfoil at his disposal, and he didn't have to fly it... > > Mark Langford, Huntsville, AL > N56ML "at" hiwaay.net > see KR2S project at http://home.hiwaay.net/~langford > > _______________________________________________ > see KRnet list details at http://www.krnet.org/instructions.html
