I'm sure most folks on the exchange are aware of the history but in light of the commercial implications maybe it's worth reviewing. Not necessarily in chronological order, or as the participants may have seen it. Just comments from an observer
The development of the S, SD, SA and AG airfoils can be attributed to a few people leading the charge but in fact is a result of modelers working with modelers to improve things for all of us. The original landmark experimental work was done at Princeton by Selig, Donovan and Fraser and later migrated to UIUC with Mike Selig and his group. If you look over the books published by Herk Stokeley, you'll find most, if not all, the test sections were built by modelers and contributed to this program. The original wind tunnel at Princeton was inspired by the need for low speed data of particular relevance to modelers. The later work at UIUC was supported, in part, by contributions from modelers. One of the important early developments leading to the Princeton work was the publication of airfoils by Dr. Richard Eppler, some of which relied on the original Eppler-Somers code for their design. That code formed an intellectual basis for later simulations and the eventual evolution of a desk top program (X-Foil) that can now be used by anyone with a PC. The original codes ran on mainframes in Fortran and were somewhat user-hostile. Additional development of an X-Foil front end is being done by modelers to provide a more user-friendly GUI. The wind tunnel data at Princeton and UIUC demonstrated that those really great Eppler foils could still use a little work. The Selig (and associate) sections were derived from those investigations and also branched out into trips, slats, flaps, and other ideas. Anyone who has flown an SD7037 or an SA7035 and compared them with an E387 will know that we got a lot of benefit from those developments. When HLG started out, it was natural to take some of the best sections from the Princeton/UIUC work and fly them. That worked pretty well but when DLG and the wide speed range demanded by this application came along, it was time for an upgrade. The work of Mark Drela at MIT pushed the boundaries of what could be measured (low speeds, small chords = lower Re than a tunnel can usefully reach). So the use of an airfoil simulation code (X-Foil and predecessors) was a reasonable approach. A lot of this work also influenced (and was influenced by) Paul MacReady's Aerovironment research which had brought us the Gossamer Condor, Albatross and the more recent solar derivatives. If you check the employee list of that company (and closely related NASA and private firms) you'll find a 'who's-who' of modelers. And keep in mind that ALL of this work is now in the public domain. The airfoils are published in user accessible libraries. The code is available as a free download. Anyone that wants to stretch the boundaries now has a theoretical tool available to create new airfoils and slap their own name on them. If you want to build a wind tunnel, the whole thing is defined in Volume 1 of the Low Speed data books. And anyone can now download any of the sections and use them royalty free. Eppler, Selig, Drela, Hepperle, Quabeck and others have given away a whole lot more than most of us could afford. For the amount of fun I've had with all of this work, I really don't have a problem with someone's name heading up the airfoil designation. They took the risk and the leadership. We were behind them at some part of the process but they provided the spark to get it done. I think anyone with an ".edu" association understands that the only thing on campus that makes money is the football team. I really don't think academicians, especially in low Re research are driving Ferrari's these days. Even if they could they probably wouldn't - not big enough to haul around their planes and stuff. And the 'one swipe of sandpaper' idea - perhaps a bit too literal. A bad AG13 airfoil will work better for DLG than a good NACA 6412. A small variation in surface distribution isn't going to corrupt the whole concept. Heck, it may even help with transition in some unexpected way and thereby benefit us all. Look at the Gossamer series. I doubt Bryan Allen's first concern was airfoil sag as he pedaled across the English channel. Probably more like "damn, that looks cold - better keep moving!" Sometimes I wish those guys HAD made some money on the deal. Based on past experience I'm confident they would have plowed it back into their research and we would have even more neat stuff. - Dave R RCSE-List facilities provided by Model Airplane News. Send "subscribe" and "unsubscribe" requests to [EMAIL PROTECTED] Please note that subscribe and unsubscribe messages must be sent in text only format with MIME turned off.
