Yellow Bird (oz10568)

About this Plan

Yellow Bird. Radio control slope soarer.

Quote: "Dave Parson's pretty little soarer won't cost a fortune to build, is easy to transport and great fun to fly off the slope or the flat with bungee assistance

I feel a song coming on, a couple actually: "Yellow bird, so high in banana tree!'' There are no banana trees in the hills where I fly, though there is the odd oak or fir tree waiting to ensnare the unfortunate or unskilful. The second song was written about Mohammed Ali, the boxer: "Floats like a butterfly and stings like a bee!" With a wing loading of about 8oz/sq.ft, this little beauty stays up well in light lift. but don't be put off with the 'stings like a bee' bit, though it has a fair turn of speed. giving excellent penetration in stronger winds or for nipping across the valley to join the family of buzzards circling in a distant thermal up-wing.

Another name for the 'V' tail is the 'Butterfly' tail, and there have been several examples of this configuration used in full-size aircraft. The Wik Salto glider, the French Fuga Magister jet, and the Beech Bonanza (a piston engined light aircraft) to name but a few. And the Supermarine Scimitar twin jet, Fleet Air Arm fighter bomber was originally conceived with a V tail.

For control, the rudder and elevator signals are mixed electronically in my Fleet transmitter and the F16B Fleet mini servos in the model do the work of moving the control surfaces via plastic 'push-pull' bowden cables, one for each servo. A word of warning: these plastic cables change length with extreme changes in temperature - cool house, hot car, etc, and in the strong sun of a summer's day. A good plan is to check the alignment of each control surface with its respective tailplane before each flight.

On a hot day when the cables expand and increase in length, I find I need full 'up' on the elevator trim; on a cold day nearly full down trim. Control surface deflections when full rudder and elevator are applied result in one surface going fully up or down and the other surface remains about level. The mixing action of these control surfaces produces some unusual flight characteristics, eg full up elevator produces the required stall condition, but the application of the rudder at the same time to yaw the aircraft to induce a spin, takes off some of the up elevator and the aircraft un-stalls. So you don't get a spin, or a spiral dive, but a sort of diving steeply banked turn. Though the aircraft is flying fairly fast, it doesn't appear to be over-speeding. but the height loss is not as much as one would like, to get down from a big thermal.

The technique here is to get inverted by means of a half loop or half roll and the application of about 75% down elevator is sufficient to maintain inverted flight, leaving enough rudder authority for directional control. Have fun with 'Cuban eights' - take off the up elevator just before the top of the half loop whilst still climbing, apply full rudder, and wait. When the half roll starts. don't be tempted to adjust the angle of the dive with elevator - it takes off some of the rudder. Roll response is excellent; by that I don't mean that it rolls well, just that there is almost instant reaction to a rudder signal - must be something to do with low inertia of the light wing. Rolls are possible, even consecutive - but slow; lots of rudder, but be careful..."

Direct submission to Outerzone.

Supplementary file notes

Article.

Corrections?

Did we get something wrong with these details about this plan (especially the datafile)? That happens sometimes. You can help us fix it.
Add a correction