Originally published December 1996
Steve Barnard, proprietor of an establishment called Barnard Aircraft Components located in Cameron Park, California, was our featured speaker. You might remember Steve's presentation to the chapter last October. He's an inveterate tinkerer who's made numerous improvements to his RV-6A over the years and turned his hobby/compulsion into a business. Barnard AC specializes in quick build kits for components of the Vans Aircraft RV-3, RV-4, RV-6, and RV-6A.
When he was here last year, Steve brought along samples of the quick build kits his company offers. Included were landing/taxi light, firewall, and wing kits. All components are cut to size, drilled (pilot or full size), precision located to the assembly point, and ready to install. Many are gold anodized and identified with a part name and number. At the time, Steve claimed a builder could save over 300 hours of construction effort. Paul Rosales, chapter secretary for the 49'ers, bought the wing kit earlier this year and will attest to the truth of that claim. You might have seen his wings at the Fox fly-in project display.
During Steve's previous visit he also showed slides of VS Aero studies performed by Analytical Methods, an engineering firm in Washington state. VS Aero is a package that does computational fluid dynamic (CFD) analysis and plots output in the form of color-coded pressure gradients on the aircraft plan form. Tufting plots can also be done, particularly where flow reversals are expected. The VS Aero data prompted him to experiment with modifications to his RV-6A's wing tips and wing roots. He also reported finding undesirable lift on the main gear fairing, poor flow at the cowling inlet, and significant drag just forward of the canopy. At the time these were just areas of interest.
The past year has been a productive one for Steve. He's validated his change to the wing tips and found another design that seems to work even better. He's also concluded his wing root modification does little to improve the flow at the fuselage but quite probably does improve stability. Another change he's explored is a plug to fill the gaps at the rudder and elevator hinge points. Foam or Dacron cloth are two materials he's tried.
Perhaps Steve's most ambitious improvements have been at the cowling inlets, through the pressure chamber formed by the cooling plenum, and at the cowling outlet. The design uses a laminar flow circular inlet located to either side of the spinner. The spinner is set out slightly using a propeller extension and the gaps inboard on the cowling at the spinner are filled. This is an area where tufting plots showed reversed flow. The plenum creates a 100% seal across the upper chamber and is designed to induct air into the fuel injection servo at about one inch of mercury over the ambient pressure at 5000 feet density altitude. His outlet redesign reduces the area from about 25 inches to 17 inches and works a stagnation point on the lower firewall.
So what do you get for all this? The average RV-6A will cruise at about 180 to 185 mph with a 180 hp engine, constant speed propeller, 8,500 feet density altitude, running 2450 rpm full throttle. Steve has an IO-360, 200 hp fuel injected engine in his RV so he's careful to qualify the improvement claims. They are impressive however. After making modifications to the wing tips, wing root fairings, cowling, induction inlet and a few other less noticeable items his cruise speed (75%) is 220 mph true at 8,500 feet density altitude, running 2700 rpm full throttle. Other stats: economy cruise is 205 mph on eight gpm fuel burn, rate of climb (solo) is 2,700 fpm, and stall with full flaps at 53 mph.
If you're looking at an RV-6 or other Van's aircraft as a project, or you've already started to build, you might want to give Steve a call. Barnard AC, 3327 Wood Lane, Cameron Park, CA. 95692. Phone/fax 916/676-5601.
Contents of The Leading Edge and these web pages are the viewpoints of the authors. No claim is made and no liability is assumed, expressed or implied as to the technical accuracy or safety of the material presented. The viewpoints expressed are not necessarily those of Chapter 1000 or the Experimental Aircraft Association.
Revised -- 27 June 1997