Radio Control: Soaring
Dan Pruss
SINCE THIS column began almost a year ago, numerous readers' requests have been received with regards to nearly every aspect of RC sailplanes. These included requests for airfoil designs and specific coordinates—where to find them and how to plot them.
The League of Silent Flight office also gets many requests as does that of the National Soaring Society. "How-to" questions include slope and thermal soaring, launching techniques, linkages for various controls, and building techniques.
Over the years a few books were published that dealt with sailplane designs. Some of these have become "bibles" to some and justifiably so.
Currently, other books are on the market and in most respects have kept pace with the state of the art and in some ways have illustrated ideas that could advance the state of the art.
The intent of this column is not to serve as a book review or to evaluate kits. However, when something becomes available that is in the general interest, efforts will be made to pass on that information.
The following books would serve you well and you are encouraged to include them in your modeling library:
Model Glider Design by Frank Zaic. Available through hobby shops; published by Model Aeronautics Publications, Box 135, Northridge, CA 91324. Price about $5.00. Originally published 1944 and reprinted since, the book has truly become the "handbook" for sailplane enthusiasts. Very heavily illustrated in model building techniques and designs. Good three-view plans of older free-flight sailplanes—scale from the pre-fiberglass era.
Model Aeronautics Made Painless by R. J. Hoffman. Available through hobby shops. The book originally sold for a dollar and is still seen at shops now and then. Not a book from which your next world-beater could be designed, but it is a book that contains a modeler's glossary and sketches to accompany the definitions. The drawings are more like ideas copied from the author's sketch pad, but this makes for interesting reading and browsing.
Radio Control Soaring by Dave Hughes. Available through hobby shops or direct from Hobby Shack, 6475 Knott Ave., Buena Park, CA 90620. Price $9.95 plus $1.20 postage and handling. Published by Radio Control Publishing Co., Ltd., 64 Wellington Rd., Hampton Hill, Middlesex, England.
Probably the best book on the subject of RC soaring. The book is full of pictures, sketches, and drawings of just about every facet of RC sailplaning. Although many articles concern slope soaring, there are chapters on pylon racing, aerobatics, thermal soaring and launching techniques.
Sketches include radio installations, "T"‑ and "V"‑tail details, spoilers, flaps, ailerons and other controls that are sure to whet the appetite of the experimenter—even if he's a two‑function devotee.
The chapter on aerofoils (’tis the British version of airfoils, y'know) is very well written and again this chapter is full of drawings and pictures. When the author begins we can agree on one thing: wings are indispensable. Fortunately for the reader, the chapter is written so that those without aeronautical engineering degrees can understand it and those with such degrees aren't insulted. The chapter also includes coordinates for the most popular Eppler, NACA and Göttingen series airfoils.
Sailplane Designer's Handbook. Available direct from the author Eric Lister, 953 Klockner Rd., Trenton, NJ 08619. Price $4.97.
First printed in May, 1973, this book was written for the modeler who leans towards designing his own sailplane, yet doesn't want to get too involved with theories he might not be too familiar with. By picking data from charts that fit the designer's basic design criterion, one can design with a certain degree of confidence.
Tables include data from some known designs so that comparisons can be made with the designer's own ideas. Sections in the book include Longitudinal Stability, Directional Stability, Do It Yourself Design, Optimized Wing Layouts for Soaring, and Effects of Wing Loading on Your Design.
Current FAI distance record holder Jack Hiner used this book for designing his "Astro Jack" wing; the rest made history.
Airfoil Selections for Flying Models. A.S.A. Test Report 03-72. Associazione Sportiva Aeromodellistica, Via S. Giovanni Bosco 21, 20081 Abbiategrasso, Milano, Italy. Price $10.00. Order direct.
This book contains the results of tests run in the A.S.A. test wind-tunnel for 16 different airfoils. Included are the following: BO 545-3/10, Clark Y, Eppler 385, Eppler 387, Eppler 392, Fukada 10, Gott 496, Gott 500, Gott 546, Hill SR-2, NACA 0009, NACA 0012, NACA 4212, NACA 4412, NACA 6409, NACA 6412.
Talking with Ferde Gale—LSF coordinator in Italy—Mr. Gale stated that each airfoil required up to eight hours of wind-tunnel tests to produce the data published. These modelers/engineers worked with Reynolds numbers of around 60,000 and the tables of data printed reflect their dedicated efforts. The book is a must for the serious designer who would care to compare the performances of the different wing sections. That's what Art Arfons used on the garage floor to design his jet drag car should eliminate this small dimension. Another item, (7) the thrust line. That's the line running from the center line of the propeller back through the entire plane. Most stuntsters line up the wing center-line no more than 1 inch below the thrust line. OK, with your diehard MB-5 it's lower, but the writer hopes that your lead-out exit from the plane is within 1/2 inch of the thrust line or you may be in for trouble. And most stabilizer center-lines are from 3/4 to 1 1/4 in. above the thrust line. If you have solid rudder/fin better put in some offset, 1/4 to 1/2 in., or make it adjustable.
The writer strongly suggests ordering a foam wing from either Arnold Stoll, 628 West 6th St., Mankato, Minn., 56001, Tel.: 507 388 2728, or from Bob Hunt, 240 Greenbrook Rd., Greenbrook, N.J., 08812, Tel.: 201 469 1663. This will eliminate a lot of pain and possible trouble with warps, excessive weight. Both manufacturers have several very competitive wings to pick from in both 35 and 46 sizes.
There you have what normally takes about 10 pages and maybe ten years condensed into a few paragraphs, but with some prior knowledge and some other plans to use for guidelines, someone who is ready to design a plane should be able to come up with a reasonably good flier. Try to get someone experienced in stunt to look at your plans before you start looking for balsa. My address is Wyman Paul, 1640 Maywick Dr., Lex., Ky., 40504.
Transcribed from original scans by AI. Minor OCR errors may remain.
