SUNBIRD

Tim Hooper builds - and modifies - a classically shaped e-soarer

- Tim Hooper

Several years ago, my wife, Netty declared her intention to build a big, all-balsa thermal soarer and was smitten by the highly individual looks of the 120” Dynaflite Bird of Time. I can't say I blame her really; the BoT has a graceful avian appearance and with its swept wing tips it's a million miles away from the uber-functional stick insects that we often see in the current competition reports.

Sure enough, Netty built her Bird of Time herself, although I helped out, both with its conversion to an electric soarer and with the fitment of air brakes in the upper surface of the wing. She elected to cover it in jet black film, with transparent yellow panels on the wing and tail's open structures. It looked great. Matter of fact, it still does.

The thing is, we were both a little disappointed with its flight behaviour, which is why it's not clocked up as many flying hours as you might expect. The carefully fettled 3S power system hauls its 4lb weight skywards in shortish order, but its glide characteristics have always seemed a little bit lacking. It ‘hunts’ in the pitch axis, vacillating between nodding its head in a series of stalls and then abruptly diving towards the ground.

We fiddled with the CG position to find the mythical ‘sweet spot’ but to no avail. Eventually, I stripped out and rebuilt the control system for the elevator (replacing the snake and tube linkage with a sturdy carbon pushrod) and this helped a bit. I say ‘elevator’ but in reality, the BoT is fitted with an all-flying tailplane of balsa strip construction and it's a very flexible structure indeed. I'm pretty convinced that this is the core of the Bird's anxieties and why she's become something of a hangar queen.