Author: Mike Garton
Edition: Model Aviation - 2003/09
Page Numbers: 102,104,106,108
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RADIO CONTROL SOARING

Mike Garton

2733 NE 95th Ave., Ankeny IA 50021 E-mail: [email protected]

This month I cover two exciting topics in the otherwise quiet world of radio control (RC) gliders. First, Phil Barnes has released an instructional video (a two-DVD set) detailing exactly how he makes vacuum-bagged wings. Phil is one of the top three professional wing makers in the country, and he shares his production methods in the video. Second, United States F3B team member Gavin Botha unofficially set a world speed record during an April contest. Below are details about Gavin’s glider and the record run. The US team is leaving for the World Championships the same week this magazine hits the mailboxes.

Vacuum Bagging Made Easy (DVD set)

Vacuum-bagging (in the context of RC gliders) is a process using a plastic bag and a vacuum pump to compress composites onto foam cores while they cure. The method allows builders to make high-performance fiberglass, Kevlar, and carbon wings at home.

Phil Barnes has been a full-time wing maker since 1996. He has supplied most of the vacuum-bagged wings for Northeast Sailplane Products (NSP) since that time. He makes wings for the Pole Cat Aeroplane Works XP-3 and parts for the Mantis glider series originally designed by Tom Kiesling.

Phil’s production quality exceeds what 99% of modelers can achieve. He has developed methods that allow him to make an RC glider wing with three to five hours of labor; this can include paint, joinery hardware, integrated hinges, and routed servo wells.

Details about the DVD:

  • Title: Vacuum Bagging Made Easy: The Production Methods of Phil Barnes
  • Length: Just under five hours (two DVDs)
  • Demonstrations: Phil constructs an XP-3 discus-launch wing and an NSP Fusion three-meter wing
  • Price: $55 plus $6 shipping and handling
  • Production quality: Good

Distribution and format:

  • As of deadline, Bill Haymaker is distributing the two-DVD set. The original release was on DVD+RW format. Efforts were being made to release it on more common DVD and videotape formats.
  • If the Web address listed below is no longer valid, a search engine should find the video by title.

Recommendation:

  • Even experienced vacuum-baggers will learn many tricks from this set. It’s a must-buy for anyone considering vacuum-bagging; the methods are invaluable.

F3B: format and influence

F3B is the contest format recognized by the Fédération Aéronautique Internationale (FAI) for choosing an RC glider world champion. F3B includes three tasks in each contest round:

  • Distance
  • Duration
  • Speed

F3B has not been widely adopted in the United States. Sport fliers often cite the initial investment in sailplanes and special F3B-legal winches as barriers. Contest organizers also note the increased manpower required to run F3B events.

Despite limited domestic adoption, F3B (and F3F slope racing) drives development of higher-performance glider structures and airfoils. Innovations from F3B trickle down to production sailplanes, improving the sport overall.

April contest in Eloy, AZ — Gavin Botha’s performance

Buzz Averill, chairman of the FAI Team Selection Committee for RC Soaring, reported on the April 12–13 F3B contest in Eloy, AZ:

"During the April 12–13 F3B contest in Eloy AZ Gavin Botha flew a magnificent 12.72 second speed run. His slowest time for the weekend (5 rounds) was 16.26 seconds. He also did very well in the duration and distance events, winning the contest over 4-time world champ Daryl Perkins, fellow teammates Darrell Zaballos, and Mike Lachowski. He also beat former team member Gordon Jennings who was flying very well. Against that bunch of fliers the rest of us were distant also-rans.

"Back to Gavin's record speed run. It seems there is no official F3B speed category in the AMA records because the AMA doesn't keep records for FAI events. Also the FAI will not recognize Gavin's record because the FAI stamp he had ordered had not been received by April 12th and therefore wasn't on his AMA license at the time of the record flight.

"Because of these circumstances Gavin cannot get official credit for what was a magnificent flight that shattered the existing record by at least 1.5 seconds.

"Furthermore, Gavin and Darrell Zaballos have been developing the model used for all of their flights at Eloy as well as the record flight for at least 5 or 6 years. The SP-1 they were both flying was out launching and out running every other model on the field. I am attaching a summary of the development process they have gone through to arrive where they are now (a dominant position)."

I requested more information about the SP-1; Gavin Botha responded with the following summary.

The SP-1: design, construction, and specs

"The SP-1 is the second F3B model designed and manufactured by Gavin Botha and Darrell Zaballos. Taking on a project of this scope is best done with at least one trusted partner. The SP-1 is the evolution of the Y2K based on several years of experimenting, investigating, analyzing, and evaluating existing designs.

"Based on lessons learned at the 2001 World Championships in the Czech Republic, it was clear that the design must be suited for all types of launching conditions. F3B events are flown from dawn to dusk in all types of weather conditions.

"The design must be capable of downwind launching at 8:00 AM and making a 10-minute duration flight. The Y2K excelled in the good conditions and experience in Northern California, but suffered in the downwind, light-air conditions in the Czech Republic.

"The SP-1 was designed to launch hard and perform in the worst conditions. Hundreds of hours were spent designing an airfoil and planform combination that would meet these objectives, yet still have good speed ability.

"The airfoil transitions from root to tip, in order to compensate for Reynolds number effects. It is 9% thick at the root and rapidly transitions to 8% at the tip. The airfoil is designed to effectively use full trailing-edge camber and is reflexed for speed. The control surfaces are a constant 21% of the chord.

"Based on the excellent distance performance of the Icon, the wingspan was set at a comparable 129 inches. Wing area was determined by trading optimal wing loadings for the distance task with launch performance requirements. The final wing area ended up 1,045 sq. in., resulting in an aspect ratio (AR) = 16.

"Female wing and stabilizer molds were CNC machined by Team Arianne. The fuselage plug was hand-carved by Darrell Zaballos, and fiberglass molds were pulled from the plug. The structural requirements for this design proved extremely challenging due to the high loads and thin wing sections, with extremely thin control surfaces. It is critical that an F3B design be very stiff in all aspects.

"The wing uses 1.5 mm Rohacell skins sandwiched between carbon cloth on a 45-degree bias. This provides excellent torsional rigidity. The control surfaces use dual carbon torque tubes to provide torsional rigidity. Lots of high-modulus carbon is used for the spar caps, to create a wing that bends very little under extreme launching conditions.

"Darrell and I have been sharing building techniques with Don Peters, maker of the Icon, for quite some time, and the SP-1 features several of Don's ideas, including the Icon-style ballast system. A 2-piece V-tail is used primarily to save weight and for convenience. Overall flying weight is 81 ounces.

"The final result is a model that performs better than expected. The SP-1 performs well in all conditions, and excels in duration, distance, and speed. After a steep structural learning curve (otherwise known as flight failures), and some fine-tuning, it was immediately evident that we had a winning design that helped Darrell and I each earn a position on the US F3B team.

"The only problem now is building enough models to be ready for the 2003 World Championships in Germany."

Gavin’s account of the record run

"The Arizona contest is always a well-run event that is always a ton of fun. I truly look forward to each year. The great people, excellent flying site, as well as record-breaking conditions definitely make this one of my favorite contests.

"The entire 2003 US team competed as a team in the Arizona contest. Having the full support of a great team (Darrell Zaballos, Daryl Perkins, Mike Lachowski, Tom Kiesling, Mike Smith, and Team Manager Jim Thomas) truly is a benefit when time comes to fly.

"Launching conditions were in 45-degree cross winds, which required hooking over into the wind, prior to climbing and building tension. A relatively good head wind allowed for maximum tension on the monofilament line. The line tension resulted in a terrific zoom and a launch height of about 1,000 feet.

"At that instant I realized that I had great conditions and the potential for a great run. These conditions were confirmed during the start dive. The SP-1 continued to accelerate all the way through the dive and well into the first leg.

"My caller, Darrell Zaballos, became an important part of the run, instantly recognizing that it was faster than usual, and called for an early roll-up and turn. In order to turn a fast time in speed you must be rolled and well into the turn before the turn horn sounds, ideally just clipping the 150 m airplane.

"I was fortunate enough to capitalize on the good conditions and flew a clean course with good energy management. Three legs later as I flew through the finish line, I knew I had a very fast run on my hands, although I was not prepared to hear that I had just turned a 12.73 second run. The feeling at that moment was fantastic.

"I continued to play in the strong thermal, fully ballasted after the run, as my adrenaline levels dropped and the reality of the run set in. I can't wait to go back to Arizona. Anyone interested in trying F3B needs to attend this contest."

F3B World Championships

  • Event: F3B World Championships
  • Dates: August 4–9, 2003
  • Location: Kirchheim, Germany
  • The World Championships website should contain daily event coverage and more information about the US F3B team.

Sources

Transcribed from original scans by AI. Minor OCR errors may remain.