RC Soaring
Mike Garton, 2733 NE 95th Ave., Ankeny IA 50021; E-mail: [email protected]
THIS MONTH I'll discuss a variety of new Soaring goodies. First is an innovative device for launching combat wings, with no hook or airframe modifications required.
Second is a new book by Martin Simons about vintage sailplanes. Third is Chris Adams' CD-ROM of technical information about the 2001 International Hand Launch Glider Festival (IHLGF).
Last, I threw in a couple more pictures from the AMA/League of Silent Flight Soaring Nationals that space did not permit me to run last month.
Nelson Johnson sent me a Wing Launcher to try. This device is a bungee with a special metal fixture for holding flying wings. In particular, it fits Zagis and similar models.
The patented (literally) innovation is the holder that does not require a hook or any modification to the Zagi—not even a towhook. How does it work?
The Zagi's trailing edge is placed against a stop in the metal fixture. When tension is put on the front ring, a hinged piece of the fixture swings down and clamps the leading edge firmly. As long as there is tension in the line, the fixture stays on the airplane.
The Wing Launcher is like a bungee—not a hi-start. When the fixture is on the Zagi, the effective towhook position is well out in front of the leading edge. This means the model maintains a horizontal flight path on tow; it does not arc up like a hi-start or a winch tow.
The fixture has a grip for the pilot's forefinger that is like a pistol. You put your finger through the grip, and walk back to stretch the rubber tubing.
When released, the airplane accelerates forward, maintaining a few feet off the ground. As it flies over the stake, the tension in the bungee diminishes and the wing-launch fixture releases the airplane. Then the pilot pulls up on the elevator and trades speed for altitude.
To test the device, I called a couple flying buddies and asked them to meet me at the park with their Zagis.
When I told them on the telephone that this new launcher costs $40, they were skeptical about the value. After they saw the Wing Launcher, they agreed it was not overpriced.
You can make one for roughly $30 in parts and a day of experimenting. Your homemade fixture probably won't be made from cold rolled steel with a couple of TIG welds.
In addition to the special fixture, the Wing Launcher comes with a stake, rubber, and directions. The rubber tubing is black, ultraviolet-resistant, 30 feet long, and 5/16 inch in diameter, with a 1/16 inch wall thickness.
The steel stake is 3/8 inch in diameter. I liked the stake enough that I am trying to convince Nelson to sell long versions of them separately.
All the regular bungee tips apply when using the wing launch. Only attempt it with straight, well-trimmed airframes. Start with small launch tensions and gradually build up to larger tensions. This ensures that the airframe is trimmed.
Do not pull up until after the airplane leaves the bungee.
Check that the stake is secure after each launch. You may even want to use a larger stake or redundant stakes, especially if the ground is not hard.
Eye protection is a good idea because you are on one end of a stretched rubber band.
We tried the wing launch with a variety of Zagis. We quickly learned the structural speed limit of each airframe.
First we tried a THL. This lightweight wing was designed for slow speeds. The first launches were uneventful, with approximately five pounds of tension delivering roughly 50 feet of altitude.
It was a good thing we started with small launches because the model did require some trim adjustment. We pulled back another five paces with each launch.
The fourth launch resulted in a large wing-flutter mode. The THL was not designed to go this fast. Once off tow, the Zagi stopped fluttering and control was regained.
Next on the test list was a Zagi LE, which made it somewhat higher. With additional tension, the LE fluttered too.
If we knew we were going to be launching these wings on a bungee, we would have applied extra strapping tape to the airframe. In hindsight, it could be applied on the outside.
The last of the Zagi tests was with the Zagi 3-C. This model has full-span carbon tube spars swept back like the wing.
A secondary, shorter carbon tube spar runs straight across the center of the wing and joins the swept-back spar. The 3-C’s wing is much stiffer than that of a Zagi LE.
The 3-C came with thin, transparent plastic winglets. These winglets fluttered even with low launch tensions. The winglet flutter did not impact controllability, so we kept increasing the tension.
We had high hopes for this stiffer Zagi but eventually fluttered one aileron. Inspection of the airplane showed that the builder taped the bad aileron too low relative to the wing. The mismatch of the surfaces made it more susceptible to flutter.
Once the tension limit for each airframe had been revealed, we backed off the tension slightly and trained a rank beginner. The new guy got to fly a bounceable airframe without a slope. Some of the Zagis did require a light up-elevator preset.
Using the Wing Launcher with Zagis was fun. It is more exciting and requires less walking than a hi-start.
It looks as though a well-built 3-C with Coroplast™ winglets would be the Zagi of choice for high launches. Nelson reports that he gets launches higher than 150 feet with this combination.
Many are using the Wing Launcher as a catapult assist for their Speed 400 (electric motor) Zagis. They start the motor via the transmitter after launching.
I am going to keep my Wing Launcher with my Zagi at all times; it will allow the fun to continue when the wind stops blowing at the slope.
Martin Simons has written a book entitled Sailplanes 1920-1945. It supersedes his previous books, The World’s Vintage Sailplanes 1908-45.
Close inspection of the two volumes reveals that the new book does cover all the gliders in the first book.
Only a couple of crude gliders before 1920 were in the first book. There is mention but less detail about the FSV series that flew a decade earlier. It is not a big loss, because the FSV gliders look like hang gliders and the details about them are sketchy.
The new book adds details about approximately 50% more gliders in the period from 1920 to 1945. The drawings have been redone in color.
Many gorgeous vintage photographs are featured in the second book, which is done in encyclopedic quality.
If you are a vintage-glider buff, Sailplanes 1920-1945 is a must-buy.
Even if you have the previous book, there are enough additions to warrant purchasing the latest one. However, if you buy the new book first, there is no reason to buy the earlier one.
Chris Adams has released his “Spilatek’s IHLGF 2001 Technical Report” on CD-ROM. He took pictures of many of the airplanes at the IHLGF in June, and he interviewed most of the pilots to get specific details about the models they flew.
Chris traced tail outlines and digitized them. Written summaries of typical construction and design practices are included.
Chris says he chose the CD-ROM format because it enables him to put much more information in the article than magazine publishers would allow. I agree. There is enough factual information on the CD for roughly three magazine-length articles.
I like the CD-ROM idea. It was a big task for one man to put together; it took three months of Chris’s spare time.
Even with three months of work, there is evidence that Chris hurried. Some of the airplane statistics I checked for accuracy did not match the manufacturer’s specifications. Even with a few inaccuracies, I commend him for the level of effort he put into the project.
Chris priced the CD low enough for the buyer to overlook the rough edges. At the time I wrote this, he was asking $12.95 including shipping and handling.
If you are like me and hunger for information about anything new in hand launch, you will buy the CD. MA
Sources:
Wing Launcher: Nelson Johnson 1100 York Castle Dr. Pflugerville TX 78660. (512) 989-2442 [email protected]
Zagi: Trick RC Products 938 Victoria Ave. Venice CA 90291 (310) 301-1614 www.zagi.com
Sailplanes 1920-1945: Raul Blacksten Box 307 Maywood CA 90270 [email protected]
IHLGF CD-ROM: Spilatek, Crawford-Adams Enterprises Box 1086 Verdi NV 89439 (775) 345-1660 www.scrollsander.com/
Xterminator Pro: Polecat Aeroworks (Denny Maize) (717) 503-9859 www.polecataero.com/
Aquila XL: Dream Catcher Hobby, Inc. Box 77 Bristol IN 46507 (219) 523-1938 www.dchobby.com
Transcribed from original scans by AI. Minor OCR errors may remain.
