RC Soaring
Mike Garton, 2733 NE 95th Ave., Ankeny IA 50021; E-mail: [email protected]
THIS MONTH I have three things to discuss: an update on discus launching, details of the new Icon thermal-duration and F3J airplane from Maple Leaf Design, and the Soar Utah Adventure video from Radio Carbon Art.
Several new discus-launch gliders have come out since the discus article went to press in the June 2001 Model Aviation. Northeast Sailplane Products has released the Logic DLG and the Psyko Logic DLG, and Mike Fox has adapted his Focus to discus launching.
These airplanes have beefier fuselage pods, tailbooms, and wings than their predecessors. The vertical fins are larger, and they extend below the booms.
Phil Barnes has been proof-testing the Logic DLG prototypes. He won the East Coast Hand Launch Classic May 5–6. Mike Fox won the Misty Meadows Hand-Launched Glider event here in Iowa the same weekend, flying his Focus DLG.
Meanwhile, the Texas Twister won at the Deep South Soaring Championships and at the Texas National Tournament. Discus launching is already dominating competitions.
In the June discus article I stated that a computer radio is required for discus launching. Adam Weston brought it to my attention that a computer radio is not necessarily required. The lack of a computer radio should not discourage a pilot from trying discus launching.
The need for an elevator preset can be eliminated by moving the center of gravity (CG) forward, as is commonly done with the Polecat Aeroworks Sidewinder. The forward CG causes the model to automatically pitch upward during the high speed of launch.
Adam related several methods for giving outward rudder during a discus-style launch without an expensive computer radio. The rudder trim can be set up so that when the rudder is centered, the transmitter trim is all the way to one side. It would be against the left side for a right-handed thrower.
The pilot trims in the outward (right) rudder before the throw. After launch, the trim lever is moved back to its left-end stop, which brings the rudder to neutral. By going to an end stop, the pilot does not need to look down.
That is the most practical method for rudder preset on a simple transmitter.
In the second method, a transmitter with dual rates (but still lacking preset switches) can be set up so that the right-handed pilot's left thumb holds full left rudder stick on launch. The launch would use the low-rate setting.
After the model has stabilized in a climb trajectory, the stick is released. Then the dual-rate switch is flipped back to high for full rudder travel.
For the third method I quote Adam directly:
"There is a proposed TX [transmitter] wiring that would allow you to put a switch and a variable resistor into any TX that would allow for a rudder offset.
"The switch would take the trim pot out of the circuit and put this variable resistor into the circuit, since the trim pot is just a 5 kohm variable resistor anyway. The launch preset would be adjusted by the resistance of the new resistor.
"I haven't personally tried this, and it would likely void any TX warranty."
More notes on discus history
Adam Weston, Phil Pearson, and especially Harold Locke have spent years refining airplanes launched by their wingtips.
These models typically have short wingspans, and are thrown somewhat like an underhand softball pitch. Although that is not discus style, Dick Barker did build on their work.
Conditions will occasionally favor the smaller side-arm airplanes. They can be launched higher and more accurately. They can also turn tighter, to stay in narrow thermals.
Thermal-Gromit Works has released the Ionosphere wing-launch glider and an expanded polypropylene (EPP)-foam wing-launch glider called the Goblin. Contact info is at the end of the column.
The late Al Nies was throwing discus style in the 1990s near Pacifica, California. This was published in the October 1996 RC Soaring Digest. Al called it a spin-launching. He was known to throw this way when the wind stopped blowing at the slope.
One gentleman pointed out that discus-style launching had been used decades before, for Free Flight gas. Apparently it gave a real advantage. I was told that most Contest Directors ruled against it in the 1944 contest season.
I would bet that others played with this launch style. I stand behind my statement that Dick Barker is credited with starting the discus-launch movement.
Although Dick was not the first, he did popularize discus throwing. His 100-foot launches of a 58-inch HLG at contests in 1999 convinced people to try discus-style.
Icon glider (Maple Leaf Design)
I corresponded with Don Peters to get some detailed information about the new Icon glider offered by Maple Leaf Design. Joe Wurts designed and computer-optimized the model. It is intended for Unlimited thermal duration and F3J.
Joe also created the airfoil, designated the JW-19. The airfoil is 8.98% thick with 2.25% camber. It has slight kinks at the flap hinge line.
As with many Quabeck and MH airfoils, the aft loading increases the effectiveness of small flap deflections. This feature usually broadens the available drag bucket, helping thermal capture and reflexed cruising.
The wings and stabilizers are built using molds taken from computer numerically controlled (CNC) machined masters, to assure accuracy.
All parts are painted in the molds with two-component acrylic urethane paint. All parts are molded with MGS epoxy, then postcured in an oven. These procedures and materials are "best in class."
The paint is several times more expensive than Krylon®, but it gives a better, harder finish. The MGS epoxy is structurally superior to its less-expensive competitors.
Postcuring gives the model heat tolerance; it is less likely to warp in a hot car. This is the way I specify that a glider be built when cost is no object.
The wing lay-up is bidirectional carbon outer skins on a 45° bias for torsional rigidity, then Rohacell® cores, then foam/glassing inner skins at 45°. There's a ton of unidirectional carbon in the spar caps, and the wing is stiff. Joe says it's the stiffest with which he's flown.
The fuselage is a three-piece molding designed and constructed for maximum stiffness. The tailboom is molded from Kevlar™ and carbon fabrics and high-modulus IM7 carbon tow. The nose cone and molded servo tray are constructed from S fiberglass cloth.
The Icon spans 130 inches. Its ready-to-fly weight is 78–82 ounces. I asked Don why it looked to be approximately 10 ounces heavier than other molded Unlimited models. I also asked if he had plans for an "Icon-Lite." His response was:
"Right now we have no plans for a lighter version of the airplane. We usually start out a bit on the conservative side, then selectively lighten parts as we learn more.
"There are a lot of airplanes out there that are lighter, but that weight alone is only half the story. This is a big airplane. At 11.50 square inches, the Icon is only about 10 oz./sq. ft. wing loading—or about the same as a 70-ounce Psycho. It's a lot bigger than an early Cobra, and stiffer, too, but it weighs about the same."
Don was right; it is easy to miss the wing area while you scan the specs. If you compare the wing loading of this model to its competition, it is roughly the same.
Compared to the nominal Unlimited airplane, the Icon has roughly 10 more inches of wingspan and 200 square inches of additional wing area.
Because of its strength, it is only fair to compare the Icon to the "nonlite" carbon molded gliders. It is not heavy in the apples-to-apples comparison.
The Icon servo tray and wing saddle were designed around the ballast system. The fuselage has a one-inch-diameter tube located under the wing and centered on the CG. The ballast tube is a series of steel tubes (the smallest is a 3/8-inch-diameter rod) that fit inside each other.
Each tube is full length (13½ inches long), so adding or removing ballast results in no CG change. The Icon comes standard with the full system; a full load is 44 ounces. You can increase that to more than five pounds if you substitute lead, or more than six pounds if you go for tungsten!
The Icon is delivered "plug and play." The carbon tube, stabilizer bracket, rudder post, ballast tube, adjustable towhook, and wing mounting system are factory-installed. The servo tray is prewired for all radio components.
The model comes with a full Hoopes Designs wiring harness, wing servo covers, ballast, and all hardware. Radio installation should be a one-evening task.
Soar Utah Adventure (Radio Carbon Art video)
Snow Peak Adventure was filmed during five days at incredible mountain slope sites in Utah. The locations include Antelope Island in the Great Salt Lake, Point of the Mountain, and Francis Peak.
As the name implies, there is coverage of the Soar Utah events for Scale and Power Slope Soaring (PSS). The PSS models are amazing to see fly. Imagine watching an F-15, an X-29, and many WWII warbirds doing aerobatics in slope lift with smoke.
Included are dynamic soaring (DS) clips. See (and hear) the Speed Runner to steady-state DS circles at 175 mph. There are also some artsy segments of Scale gliders soaring gracefully at sunset.
Paul Naton has elevated Radio Control glider video to professional standards. He used a digital camera, edited digitally, and added New Age–style music from the Spotted Peccary music label.
It is well worth the money to see gorgeous airplanes flying in exotic places. I give it five of five stars for content and quality. I hope Paul Naton continues to produce glider videos. M4
Sources
Thermal-Gromit Works 4742 42nd Ave. SW (#562) Seattle WA 98116 (206) <REDACTED> www.tgworks.com
Icon Glider: Maple Leaf Design Carquinez Ave. El Cerrito CA 94530 (510) 524-8500 www.mapleleafdesign.com
Soar Utah Adventure video: RadioCarbon Art Box 2311 Corvallis OR 97339-2311 (541) 752-9661 www.radiocarbonart.com
Transcribed from original scans by AI. Minor OCR errors may remain.
