[Headline: Reinventing the Kaos]
Happy holidays. I hope everyone received the RC gifts of his or her dreams!
Joe Bridi’s Kaos is an iconic airplane that has transcended generations of modelers. Joe’s original Kaos construction article was published when I was first learning how to fly RC. My jaw dropped the first time I saw a Kaos flying the pattern. Even today, a Kaos in the air always brings a smile to my face.
Forget Kaos variants such as Super, Killer, Ultimate, Utter, etc. My favorite is, and always has been, the original Kaos—boxy fuselage and all. My father once said, “Everybody should own a Kaos; that’s one good flying airplane.” In my dad’s memory, I offer my fourth rendition of Joe’s magnificent Kaos.
A Kaos isn’t a Kaos until it’s been modified. Modification is part of plans-building fun.
The lack of glow engines or support equipment led to making this Kaos electric-powered, with tricycle landing gear, an 11 x 7 propeller, and a high 880 Kv helicopter motor. Thanks go to Don Atwood for discovering the T600 motor from HobbyKing and Rex Lesher for his initial flight testing. Although the T600 doesn’t make the sound of a cross-scavenged .60 from the late 1960s, it spins a 12 x 8 propeller at a higher rpm.
Lengthening the original Kaos’ nose is a typical modification for retracts. To accommodate a 5S or 6S battery, the fuel tank compartment needed to be extended by 1 inch.
The ESC is mounted under the battery tray and exposed to the cool slipstream. The T600 is a front-mount motor requiring a new (second) firewall farther forward on the nose cheeks. The nose gear is mounted to the original firewall.
Many years ago, I watched an old, oil-soaked Kaos come in for a landing. When the nose touched down, it broke off in front of the wing. Conscientious that the nose was a weak point in the design, I beefed things up without much of a weight penalty. The fuselage sides are laminated with plywood from the wing’s TE forward.
Helping to counterbalance the heavy battery in the front, the elevator and rudder servos are mounted in the tail.
The wing of the Kaos was reengineered by my CL pilot friend, Pat Johnston. Pat’s CAD skills and laser cutter are invaluable resources and greatly appreciated. To reduce weight and take advantage of the laser’s accuracy, an I-beam-type spar box is incorporated. Heavy maple wood landing gear blocks are replaced with lighter plywood/balsa assemblies. Two aileron servos are mounted in the wings.
Pat was provided an original set of kit ribs to use as a CAD rib pattern. We are excited about the next modification, but understand that many may roll their eyes.
I have read that Joe Bridi used his shoe as a French curve to draw the Kaos’ airfoil. Pat found the Kaos’ airfoil similar to the +P airfoil he uses in CL Stunt designs. The +P is much like the full-scale EAA One Design airfoil and known for producing a lot of lift-per-drag ratio with pronounced stall at a high angle of attack.
The rib profile forward of the spar was redrawn as an ellipse, slimming the camber of the original airfoil by a pinch. The chord and wingspan remain the same. If there is enough interest, Pat will laser cut wing kits this coming spring.
An old kit was used as a guide for cutting fuselage and tail parts for the Kaos from contest-grade balsawood on a band saw. After years of building, I have concluded that wood choice makes a significant weight difference. In round numbers, 6-pound contest wood is half the weight of typical kit wood.
Painting the Kaos will be detailed in a future column. I have my eye on a newly discovered product for applying paint without spray equipment. I am anxious to try it.
I received many positive responses to my March 2014 column about painting the Black Magic. The aircraft was sold after it was painted. Perhaps its new owner, Karl, will provide some pictures of the finished airplane and a flight report.
Sportsman of the Month
Boise Area Radio Kontrol Society club member, Karl Watts, is our Sportsman of the Month. Karl dabbled in RC Aerobatics for several years before becoming a contest regular this past season. Let’s give him a warm Pattern welcome!
National Society of Radio Controlled Aerobatics (NSRCA)