Frequently Asked Questions
Bob Aberle | [email protected]
What kind of aileron?
Please write in with your questions; that is the only way we can keep this column format going. When referring to already published questions and answers (for followups), always provide the number as a reference.
Also note that references to addresses and Web sites are placed in a group, separate from the text, at the end of this column under "Sources." A "Tips" feature is provided in addition to frequently asked questions; these hints are numbered in the same sequence as the questions and answers.
Q493: "I have noticed on some airplanes that the ailerons run the full length of the wing, while on others the aileron is only approximately the outer half of the wing. What is the difference? Is there a difference in the flying characteristics? Is there a relationship between the area of the wing and the aileron? Also it seems that low-wing airplanes always have the full-length ailerons, while high-wing airplanes have both. Any information you may have would be greatly appreciated."
A493: This is both an interesting and important question. I have used full-length strip ailerons on my sport models and the "barn door" type on the outer wing panels of my scale aircraft. I asked my flying buddy, Tom Hunt, for his thoughts on this subject.
After reading the question, he indicated that his input would probably not answer all of the questions on this subject; doing so would require a full chapter in an aerodynamics book. But for those who are interested in a "starter course," following is his response.
"Years ago, when servos were big, heavy and more expensive, strip ailerons were actuated by a single servo. The aileron extended nearly all the way to the sidewall of the fuselage and was deflected via a short torque rod.
"There was no good aerodynamic reason for doing this; in fact many designers did not give the aileron enough chord to be aerodynamically efficient. Many models suffered from poor roll control with strip ailerons, and increasing the throw only compounded the problem by introducing a problem called adverse yaw (model banks left, but yaws to the right and vice versa).
"Good strip aileron designs used ailerons that had chords of at least 20% of the entire wing chord. Since manufacturers of kits did not want the expense of making tapered aileron stock for tapered wing planforms, one always saw constant-chord ailerons on all wing designs (tapered panels or constant-chord panels).
"Ailerons that do not taper with the wing are not necessarily bad, just a compromise of manufacturability and performance. Too much chord and too little span can be as bad as too little chord on a full-span (strip) aileron.
"Big barn-door ailerons found on just the outer half of the wing are susceptible to flutter and, without proper differential deflection (more up aileron than down), this type of aileron can also create an adverse yaw condition.
"The position of the wing on the fuselage (and the type of aileron) has very little to do with roll control. Size (percent chord and span) is the main influence on roll control.
"Today's 3D aircraft need large amounts of aileron area on the inboard sections of the wing to try to counteract the torque of the engine/motor and propeller system during the hover phase of flight. This excessive area becomes a burden in normal horizontal flight at higher speeds, and if not designed correctly (mechanically) can cause some very serious flutter failures and possibly crashes.
"Larger 3D models use multiple high-torque servos on segmented inner and outer half aileron sections to reduce this risk."
Thank you, Tom! If you want to add your comments on this subject, please drop me a note.
Q494: "My question concerns making cowls from material other than balsa.
"I am completing a WACO E which requires a 6-1/4-inch-diameter cowl. I’ve tried working with fiberglass over a foam mold and did not care for it. Could you give me some other ideas for building a custom cowl?"
A494: Not to sound commercial, but there are companies that make a variety of molded fiberglass cowls for model aircraft. You can use any Internet search engine to locate the suppliers. One that comes to mind is Fiberglass Specialties; this company has been around for a long time. I’ve listed the contact information in Sources.
One of the techniques I’ve used throughout the years has been to make a mold for a cowl from layers of 3/4-inch pink insulation foam. You can get that material from The Home Depot.
I use a bandsaw to rough out the foam block and then sand it to shape. Then I apply a layer of Saran Wrap over the mold and add one or two layers of thin fiberglass cloth over the Saran Wrap. Following that I apply slow-curing epoxy cement or polyester resin over the cloth.
The final step is to envelop the mold, cloth, and cement with a large rubber balloon. You literally stretch the balloon over the entire mold. This brings the cloth and cement in perfect and even contact with the mold. After curing overnight, I remove the resulting fiberglass shell from the mold and trim it to fit my model.
This technique was well documented by the old Pettit Paint Company's Hobbypoxy Division, which is no longer in existence. If anyone has a copy of the "Balloon Method" application sheet, please send it to me so I can share it with readers.
Q495: "A friend of mine mentioned that he saw a small flying wing design that was electric powered and had no vertical flying surfaces at all. In other words, the airplane was simply a flat triangular-shaped wing.
"Based on this information can you locate the design for me?"
A495: I got lucky with this question, because a fellow Silent Electric Flyers of Long Island club member has built one of those models. The design appeared in a British publication that is part of Traplet Publications.
The model is called the Simplicity, and John Rutter designed it. It has a wingspan of 24 inches, and the area is 380 square inches. The total weight, with a small brushless outrunner motor and a two-cell Li-Poly battery, is 5.35 ounces.
The airplane appears to be constructed from approximately 3/8-inch-thick white foam. The interesting part of this design is that it is flat, with no vertical surface such as a fin or rudder. It is flown with elevon and motor control.
I've seen this aircraft in flight, and it is amazing. It is totally stable and requires no gyro control; you simply fling it to launch as you hit the throttle.
It shouldn't take more than a couple of hours to cut out, install the equipment, and head for the flying field. Because it is made from common foam sheet, it won't cost much either.
Traplet Publications does sell the plans; I've included contact information in the Sources section. The Web site can be tricky at times, so please be patient. I've also included a photo of the Simplicity that I saw fly.
Q496: "For many years I read magazine construction articles authored by noted scale builder Walt Mooney. Did anyone take the trouble of accumulating all of Walt's wonderful plans so that we might revisit them today for micro/indoor RC flying?"
A496: I found exactly what you are asking for in Pat Tritle's column that was published in the December 2010 Flying Models magazine. I've included the Web site address under Sources. The page contains tons of Walt's plans, which can easily be enlarged and printed at stores, such as Staples, that have copy centers.
The page included much more, including sections titled "Those early years," "Old time rubber endurance," "Kit and dime scale plans," "Pnuts and Pistachios," "FF scale power," and much more. Give it a try; I think that you will be pleased.
T497: AMA member Bill Gaston was kind enough to mention a wonderful facility in his area of Texas: the Pioneer Flight Museum, which is part of the Vintage Aviation Historical Foundation. The museum is located at the Old Kingsbury Aerodrome, which is 10 miles from Seguin and roughly 40 miles east of San Antonio.
The owner built the Aerodrome to look like a World War I airfield. Right now it has six full-scale WW I aircraft that have been restored to flying status. It's similar to the Old Rhinebeck Aerodrome in New York, but it's located in the middle of our country.
I've included contact information for the facility. The Web site features scheduled events, the aircraft, photos, and what's planned for the future. Thanks for the tip, Bill!
Sources
- Fiberglass Specialties Inc.
(479) 359-2429 www.fiberglassspecialtiesinc.com
- Traplet Publications
+44 (0)1684 588500 http://shop.traplet.com
- Walt Mooney designs
- Pioneer Flight Museum
(830) 639-4162 http://pioneerflightmuseum.org
Transcribed from original scans by AI. Minor OCR errors may remain.
