FREE FLIGHT SPORT
Gene Smith, 1401 N. Husband St., Stillwater OK 74075 E-mail: [email protected]
MASTER MODELER
Bob Schlosberg shared a photo of his beautiful rubber-powered Pitcairn Mailwing. He is using a 9 x 11 propeller finished from a Superior Props blank. Bob’s other biplane is based on the Negabipe—a Bostonian designed by John Tudor and published in the March 1983 Flying Models. Bob enlarged the Negabipe to 31 inches in span and made some changes to the wing planform.
The model uses a 10 x 12 Superior propeller. According to Bob, it is flying great with two loops of 1/8-inch rubber and two loops of 3/16-inch rubber, 34 inches long. The N number is in memory of the Schlosbergs’ late daughter Carol’s birthday.
The Fokker D.VII and Nieuport XVIIIC are the work of Norman Becker. The Nieuport is a change of pace from the class C Witch Doctor he used to fly in contests in the Midwest. The Nieuport uses an 8-inch Peck-Polymers propeller and two loops of 3/16-inch rubber that is 18 inches long.
The center of gravity is the center of the top wing. The model weighs 50 grams and puts up consistent 40-second flights. Norman built the Nieuport from Megow plans, which are available from Allen Hunt Plans, Box 726, Dunbar WV 25064. The 2800 plans catalog is $10, refundable with the first order, or order online at www.modelairplaneplans.net.
I have read several opinions on the best way to set up the incidence between a scale model biplane’s upper and lower wings. The consensus is that if the wings are in the usual configuration, with the leading edge of the lower wing slightly behind the leading edge of the upper wing, the lower wing should have approximately 1° more positive incidence than the upper wing.
The rationale is that the lower wing is operating in the downwash of the upper wing and needs a bit more incidence to develop lift. I plan to build a biplane soon and see how that configuration works.
Why Doesn’t the Darn Thing Fly?
The Peanut Scale Goodyear racer mass-launch is one of the Flying Aces’ newer events. I have always liked the Boo Ray; its appeal is a combination of streamlined design and the white-and-red finish. It is a modified version of the classic Cassutt Goodyear racer.
I had Dick Howard plans for a Cassutt II and used them as the basis for a Peanut Scale model of the Boo Ray. I modified the outlines using three-views of the Boo Ray from the book The Air Racer by Charles Mendenhall.
Despite my best efforts it came out overweight, at a portly 16 grams. I thought the relatively large wing area would help, but the model didn’t want to fly. I knew from experience that there was plenty of dihedral, but the model was directionally unstable. After small adjustments it would either make a sharp right turn or a sharp left turn. I thought the large fuselage area behind the wing would make an adequate fin, but I was mistaken.
I added a quarter inch to the height of the fin, and then the model tracked well. In retrospect, Dick’s plans for the Cassutt II had round fins on the tips of each stabilizer, and I did not account for that lost fin area when I modified the plans for the Boo Ray tailplane. After the modification the Boo Ray tracked well for 10 or 15 feet, after which it either dived or stalled. Longitudinal stability was the remaining problem.
I added clay to the nose until it looked like the little racer was sporting a radome. Even with the center of gravity at 20% and negative incidence added to the stabilizer (the rear of the stabilizer was raised), the airplane was unstable. A check of the stabilizer area showed it to be 19% of the wing area. That just wasn't enough on such a short-coupled model.
A quick run of the stabilizer plans through the copier brought its area up to 25%. The new stabilizer completely changed the model. It flew well, considering that the wing loading was roughly equivalent to that of an anvil with wings. Now the Boo Ray is a respectable sport flier—not competitive, but fun to fly.
Adventures in Trimming a Maverick
One of the best 1/2A Gas Free Flight model designs of the 1980s was the Maverick. The design is still competitive in AMA Gas events, and sometimes it gives modern F1Js a run for their money.
During an F1J flyoff at the Muncie Nationals last year there was a Maverick in the midst of a gaggle of high-aspect-ratio, multifunction F1Js. The Maverick wasn't the last model down, but it wasn't the first.
Campbell's Models has an excellent kit of the design. The only change I made from the plans was to cap the bottom of the diagonal wing ribs with carbon-fiber strips. I used my current covering of choice for 1/2A Gas models: UltraCote Lite. It is extremely easy to apply but, as with all plastic coverings, doesn't add much rigidity to the wing.
On the fuselage plans, no support is shown for the rear of the stabilizer. Be sure to put at least a 1/8-inch platform under the rear of the stabilizer. I installed a 2-56 screw in that platform so I can adjust the stabilizer incidence with the screw. Epoxy a small piece of razor blade to the underside of the trailing edge of the stabilizer where it meets the adjustment screw so that the screw doesn't eat into the stabilizer. The screw is contained in a 1/2-inch length of yellow Nyrod.
My trimming problems began with a bit of inadvertent left thrust. I knew it was there, but I have several pylon models that need a bit of left thrust so I did not correct it. For all test flights the model was launched to the right of the wind with the wing in a slight bank to the right.
Immediately after launch the model would level its wing and climb straight ahead with a slight roll to the left. Since the model does not have auto surfaces, it has to turn to properly transition from the power phase into the glide. Without the turn the model will stall and lose considerable altitude when the engine quits.
I tried several things to establish a right turn. I added shims to the fin and removed washin from the right wing. The power pattern remained the same.
Finally I removed the small amount of inadvertent left thrust and removed some of the right-turn shim from the fin. With the engine straight ahead except for the specified 3° of downthrust, the power pattern improved considerably. The Maverick had a nice right turn.
When the motor run extended beyond three seconds, a new problem developed. As the model gained speed in the climb, it would suddenly level out. I had seen this with my first Maverick, and it was caused by the leading edge of the stabilizer lifting off of the stabilizer platform.
I cured that problem by notching the stop on the front of the stabilizer platform so that the rubber bands could pull down against the front of the stabilizer. I tried the fix on the new Maverick, but it didn't help.
The only other thing I could think of was that the wing might be flexing at high speed despite the carbon fiber on the bottom of the diagonal ribs. I raised the covering on the main panels, added a carbon-fiber strip to the top of each diagonal rib, and replaced the covering. That turned out to be the fix the model needed. I was able to extend the motor run and the model had a consistent right-hand pattern with a nice transition into the glide.
NRG Plans
Bob Hanford designed and built the neat NRG (say the letters rapidly out loud) in the late 1940s. He flew two versions: the stick model shown and a Wakefield version with a pod over the wing and a retractable landing-gear fixture.
Both versions are contest winners. The Wakefield qualified for the 1949 Wakefield team but was lost on its last qualifying flight. Bob had to use a backup model at the World Championships. These models are eligible for the new National Free Flight Society old-time Rubber events: Nostalgia Rubber and Nostalgia Wakefield.
Bob was a draftsman for Chance Vought and has produced an excellent set of plans featuring both versions of the NRG. The plans are full of good details, which will help you reproduce the model and its folding one-blade propeller.
You still have time to build one version or both for this contest season. Each has a distinct fuselage, but they share a common wing and stabilizer. Send $8 to Bob Hanford, 6566 E. 21st Pl. Apt. 163, Tulsa OK 74129 to get your plans postpaid.
Transcribed from original scans by AI. Minor OCR errors may remain.
