Warbird Pylon Racing

Written by Don Stegall Get into the excitement of racing at this year’s Nats Photos by the author As seen in the May 2016 issue of Model Aviation.

With the upcoming 2017 AMA RC Pylon Racing Nats just around the corner, I’m going to share details that might benefit people and clubs that want to get involved in warbird racing. Radio Control Pylon Racing Organization (RCPRO) Warbird Racing and some of the warbird racing groups in California are based on similar concepts. Similar to AMA Pylon Racing events, there are tiers of performance, but the airframe and engine rules for these classes are more open than AMA Pylon Racing. California-style racing uses a wing-area-to-engine-displacement chart. RCPRO racing no longer has a wing-area chart. In RCPRO racing, the only wing specification is that the wing area must be 400 square inches or more. The wing-area chart was dropped because wing area to displacement can favor some engine and airframe combinations. With the advent of electric power using brushless motors and LiPo batteries, it becomes difficult to specify the power system. But these wing-area charts set some limits concerning speeds that can be achieved. There are pluses and minuses to each, and this can be a real “conversation starter.” At the 2016 Warbird Racing Nats, a wing-area chart is specified and electrics will not be competing. The question is, “How do you have tiers of performance when so many powerplant and airframe possibilities exist?” The answer is brackets. Bracket racing is not a new concept. It has been done in automobile drag racing and in closed-circuit car racing. In Pylon Racing, a standard course has been defined and brackets have been established for that course size. The current and most popular course is a two-pole, 700-foot course. Three classes of aircraft performance have been established. Bronze is the slowest of the classes with a breakout time of 2 minutes and 30 seconds. Silver class has a time of 2 minutes, and the breakout time for the Gold class is 1 minute and 30 seconds. A breakout time is the minimum time you can post in a heat and not be penalized for going too fast. This is somewhat foreign to people who are accustomed to many types of racing, where the first person to finish the race or heat wins. The purpose is to limit how fast the airplanes can go in their tiers. To get a 1-minute-and-30-second time in the Gold class, you don’t need a model capable of 200 mph; a 150- to 175-mph airplane can win a Gold heat race.

The RCPRO Warbird Course will be used for the Warbird Pylon Racing event at the 2016 Nats. It is designed for safety and is used for waivers for sanctioned warbird events in RCPRO and RCPRO-derived class races. The breakout times are established for this course.

Pilots and callers are getting their strategy together for a heat race. In bracket racing, there is an element of strategy to race as fast as possible without beating the breakout time.

The pilots fly from off the course facing the pylons. This is a heat in a Silver-class race.

As in nearly all forms of racing, preparation and consistency are key to winning. Many of the airplanes flown in warbird racing use retractable landing gear. Having landing gear fail or perform poorly on takeoff will get you no points if you don’t get the airplane off the ground. Having a gear failure on landing can damage your aircraft to the extent that you might not be ready for the next heat. Retractable landing gear makes an aircraft significantly more complex. In fact, in full-scale general aviation, an airplane with retracts and a variable-pitch propeller is described as “complex.” Because the type of racing I am discussing has no limits on engine or fuel system modification, the key is having both be reliable. Some of the models use YS or other brands of engines with pressurized fuel systems. Proper preparation of a pressurized fuel system adds to the performance and complexity involved in running those engines. Contestants provide their own fuel. Some run 50%, 60%, or 70% nitro. With the high nitro content, engines can and do fail.

This is the YS115FZ-WS Warbird Special engine. It is an evolved version of the YS110 and fits in the same mounting pattern.

Propellers are not limited. Matching a propeller with an engine and an airframe is an art. The Gold-class aircraft tend to be the most complex and highly tuned. With the breakout times, the fastest, most-tuned model might not win. All of the pieces have to come together. The good news is that you can take nearly any semiscale warbird ARF and be competitive in the Bronze class. One of the most popular models for warbird racing is the P-51 Mustang 46, offered by The World Models. This airplane has a wooden wing, fuselage, and tail, with a fiberglass cowl. The World Models also offers the Voodoo Mustang 46 and the Dago Red Mustang, both with similar planforms. With good assembly skills, aircraft from other manufacturers can also be set up for the Bronze class. The speed of a competitive Bronze-class model should be in the 100 mph to 120 mph range; however, an 80 mph model can compete in Bronze and even win.

Choosing an airframe and engine combination for the class in which you want to compete is key. An unreliable airframe and engine combination won’t win. You can search for advice on the RCUniverse forum or the RC Warbird Racing page on Facebook. People are generally glad to share their choices and preferences. When it comes to the higher classes, some construct purpose-built models, while many modify and reinforce ARF aircraft. It can require significant effort to make an ARF hold up to the speeds required to compete in the Gold class, but some manufacturers produce models that do hold up to Gold-class speeds. One of the newer models in the marketplace is the Spitfire 40 by The World Models. Although it has 40 in the name, this model was built to be able to handle the YS115FZ-WS (Warbird Special) by YS Engines. YS engines are popular. The YS FZ63S works well in the Bronze class; the YS91 does well in Silver; and the YS110 and YS115 engines are popular choices in the Gold class. All of these engines are crankcase supercharged and have pressurized fuel systems that perform well on the straightaways and in the turns. The Spitfire 40 has electric retracts, a strong wing, and solid balsa tail surfaces. The solid surfaces make it too tail-heavy for a .46 two-stroke engine without significant weight added up front. The YS115FZ-WS weighs approximately 26 ounces and the airplane will be slightly nose-heavy if assembled according to the manual. Shifting the throttle servo rearward and putting the receiver behind the servos can balance it.

The World Models Spitfire 40 was built for Warbird Pylon Racing. It features a strong firewall with enough space for the YS115FZ-WS engine. Many other engine brands will easily fit.

The Saito FA-125A AAC with a muffler weighs 22 ounces. If you want to go with a two-stroke engine, the relatively new O.S. 95AX Ringed engine with muffler weighs 20 ounces. The older O.S. 91FX Ringed engine with muffler is in the 20- to 24-ounce range, depending on the muffler. There are no muffler limitations other than two-stroke engines need to have a muffler or a tuned pipe. Jett Aerotech has a variety of engines that can be used and offers mufflers for other engines if you need a performance boost. Richard Verano of YS Engines and Pylon Racing fame had significant input on the Spitfire 40. I spoke with him about tips and modifications for Gold-class racing and I purchased a YS115FZ-WS to go in mine. I plan to make videos about the Spitfire and the YS engine, as well as other warbird racing aircraft, and share some tips from Richard. Check out my videos at the link listed in the “Sources” section. If you are racing under RCPRO Warbird Racing rules and are not limited to .95 displacements for a two-stroke engine, there is one gas engine that might be fun to try in the Spitfire 40. The Evolution 20GX 20cc (1.20 cu. in.) gas engine with a pumped carburetor might work in the Spitfire 40 if the ignition is relocated, and possibly with the use of a header and tuned pipe instead of the Pitts muffler. With the price of gasoline being low, fuel would be inexpensive—much less than 30% to 50% nitro per gallon. Fans of electric-powered aircraft should note that they are being raced in RCPRO Warbird Racing events and winning. Tony Pacini was a pioneer in electric power and he has been at the top of the leaderboard multiple times. With the addition of Club 40 and Warbird racing at the 2016 AMA Pylon Racing Nats, there is something for almost anyone interested in RC Pylon Racing in Muncie this summer. —Don Stegall [email protected]

Sources:

Nats www.modelaircraft.org/events/nats.aspx Nats Warbird Championship Race Rules www.nmpra.net/Documents/2016nats warbirdracerulesapproved160107.pdf RCPRO Warbird Racing www.rcprowarbirdracing.com The World Models/Airborne Models [email protected] www.airborne-models.com YS Engines www.ysengines.net Jett Aerotech (713) 680-8113 www.dubjett.com Horizon Hobby (800) 338-4639 www.horizonhobby.com Author’s videos www.youtube.com/user/donstegall/videos National Miniature Pylon Racing Association (NMPRA) www.nmpra.net