GW Yak 54 Test Flight Report
First off, I have to again thank Pro Bro Alfster for setting me up with this Yak, and the guidance when finishing it. Thanks Bro!
The set up is as follows:
Himaxx 2015-4100 with a GWS "D" gear drive and a GWS 12x6
Castle Creations Phoenix 10 ESC
Kokam 3S 1500 mah LiPo (4 ounces)
Hitec Feather (gotta get a Berg one day…
(2) HS-55 servos and (2) Cirrus CS-21 (HS 55 clones)
The Yak finished at 10.75 ounces without a battery.
CG at ¾ of an inch AFT of the spar
(Plug that into your MotoCalc!)
The plane launched just below half power, and slowly climbed out at about 10 or 15 degrees of climb. Once flying straight, trim was minimal. I flew a couple of 50 foot laps to get a feel for control response, then started to 3D the plane.
Everything was great, except the rudder. I may have some flex somewhere, as the rudder was drastically out performed by the ailerons and elevators. I'll re-check the set up, before the next flight.
Harriers are a natural for this plane. It will cruise along at power with a few degrees of up attitude. Even at 14+ ounces, the Yak could be flown very slowly like this. It didn't take much power to keep a walking speed flight going. Even at a shallow angle of attack and very slow speed, the yak felt like control authority was good enough to feel confident at low altitude. I throttled back and pulled into a clean 45 degree harrier, and it didn't take much elevator to hold it there. The wings did not seem to rock, even with the gentle winds of the day. Inverted, the plane was less stable, probably because of all of the weight of the battery now being over the plane. The pendulum effect wanted to roll it back over. After a few seconds of playing with the ailerons to find the sweet spot, it calmed down a bit and became a bit more stable.
Hovering was tough, as the wind would pick up a bit every now and then. It was hard to see what was the wind bumping it around, and what might just have been an instability issue. When the wind died, I felt like it was hovering all but straight vertical, and it torqued extremely fast. I'm thinking that in no wind, it was near one rotation per second.
The knife edge was good at speed, but at high alpha, the previously mentioned rudder authority issue showed itself. The Yak also showed very minor roll coupling following the rudder.
Waterfalls were fast, and needed a bit of rudder to keep straight, on the upward part of the rotation (the last ½). It wanted to fall off into a knife edge spin. I was using left rudder more times than right to correct.
Walls were perfect, a full 90 degree pop up and rock steady after that. There was no need for rudder correction in a wall. Even from a crawling harrier, the elevator would rotate the last 45 degrees and then start to tail slide. A burp of power got me a head high torque roll that, somehow, I didn't expect. I should have seen that one coming.
Snaps were pretty clean, and if held to full elevator and rudder, could be stopped deep in the snap, nose up in a hover. That's my favorite move with this one. Fly full power, and snap with full control deflection. Throttle back as the plane finishes the rotation, and hold the elevator and rudder. When vertical, let the controls center, and it will stop in a hover. It is much cooler than doing a wall into the hover.
All in all, the plane easily rates an "A+". Even if I never find any more rudder authority, the plane is great. As my comfort level improves, I plan to see just how low I can torque and hover. The plane acts like it's waiting for me to get better…