Electric Flight - September 2013

RC Factory/Icare RC Crack Yak Lite

The small MP Jet brushless outrunner was a great match to the airframe. My ply disc has four pieces of thin CF glued into the foam front end “cross section” for added support. A couple of different props were tried with fairly similar results.

The printing on the model is quite crisp and clean. A small slit cutout for the battery allows for some CG changes if wanted.

Lighten Up!

The spirit of the Lite Series Crack Yak 55 is an indoor/outdoor 3D aerobatic airplane that will withstand the abuses of tight spaces, inadvertent “touchdowns” and the learning curve of extreme flight maneuvers. Lighter is better with this style of model and here is the best way to enjoy light flights:

Component choice is everything. When it comes to power, follow recommendations on the lower end. The Crack Yak will accept a 2203 or 2204 motor; use the 2203 and get a higher Kv if you have the need for speed. Make sure to also use a lightweight speed control and servos. Every gram really does add up on a model this size.

Glue choice is up to you, but I’ve had great results with contact adhesive such as Welder’s, which evaporates and loses weight while it dries! It has another advantage: it is not as brittle as CA. Either way, be sparing with your glue and only use enough to get the job done; more glue is more weight.

Extreme measures can be executed if you are a weight-saving fiend like me. I have been known to remove the four screws holding a servo case together, remove the bottom of said case, shorten servo wires (even the internal ones!), shorten motor/speed control wires, remove battery balance leads, remove receiver cases, remove shrink wrap from speed controls, and even leave off landing gear (which is against my model airplane religion). I have to add that such modifications may void warranties, so check with your manufacturer/distributor to be sure.

UniqUe featUres

The “Lite Series” of Crack Yak airplanes are the result of a proven design on a diet, shedding 1.5 ounces. The Crack Yak’s airframe parts are all pre-printed. It used to be that EPP planes (while being highly durable) were a little too flexible and their precision flight capabilities suffered in comparison to Depron planes. The Crack Yak Lite is uniquely rigid and, once built, offers an unusual crispness for an EPP model. A pair of pre-beveled EPP foam trusses adds even more stiffening with minimal weight gain and further lowers the wing loading. Four-ply ribs hold the twin carbon-fiber wing spars in place and once glued in, the assembly stiffens the wing well.

Your components are all located centrally and this aids lateral balance. Remember to use your lightest gear!

The aileron hinges and the empennage hinges are molded into the wing and tail feathers. You will want to fold all of the control surfaces over and allow them to sit overnight under a book or other flat weight. This will help loosen up the hinges and make them easier to move thus giving a bit of relief to your actuators. When it comes time to install the servos, the pre-cut openings may have to be modified to fit your particular servos. This is quick and easy with a sharp hobby knife. I made a slit in one of the foam trusses and was able to conceal most of my wiring inside, which