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I Knew It! – Where RC Airplanes are Leading Me

Posted by Tom Benedict on 13/02/2013

I’m starting to see a pattern…

When I was a kid, I loved kites. The idea that something that had no power source of its own could fly was fascinating. It was even more fascinating to tie payloads to my kite string and lift them as well. (Those little green baskets that strawberries used to come in were awesome for making gondolas!) I should have known it was a sign of things to come.

Years later I got into sailing. I’d been on power boats, but they just didn’t do it for me. Again, I think the fascination had to come from the idea of being in a vessel that had no inherent power source, but that still moved through the water with ease. No surprise, my wife and I gravitated toward catamarans – some of the most efficient sailing vessels ever made.

When I got into aerial photography, I guess it was only natural that I returned to kites, albeit seriously upgraded from the ones I used as a kid. Using kites for aerial photography offers serious operational benefits, such as the ability to sit in one location for hours, if necessary, until the light happens. But it has non-photographic benefits as well that go back to why I got into kites and sailing in the first place: the silence, the power, the peace.

And now I’m getting into RC airplanes. For a variety of reasons the plane I chose has a large high-aspect wing, low wing loading, and a decent glide slope. These are all features you want when sticking camera gear on an airplane. But they benefit something else as well: using the plane as a glider. And the more I fly it, the less inclined I am to use it for aerial photography. It’s just too fun to fly! And the more I fly it, the more I find myself cutting the motor entirely and gliding. Just like flying a kite, flying a glider is therapeutic.

The problem has been finding places and times when I can fly. The wind around my house ranges from moderate to torrential. But it’s almost never zero. When I got my plane I thought that kites and airplanes would fill two different parts of the wind regime: zero wind = airplanes, moderate wind = kites. Too much wind means the plane stays home. And there’s almost always too much wind. I thought I was stuck. But all that changed when I discovered slope soaring.

When wind encounters a slope, hill, cliff, or even a generously sized building, the wind has to go up and over the obstruction. This creates an upward moving body of air just in front of and above the slope. Put an airplane in that body of air, and it flies. And since energy is being pumped in in the form of upward moving wind, the airplane can theoretically fly indefinitely, just like a kite. This works so well, the airplane doesn’t really need a motor at all. All it needs is enough oomph to be able to use the lift from the wind and turn it into speed.

There are, of course, idealized regimes of airplane design that lend themselves to slope soaring better than others, just as there are idealized regimes of automotive design that lend themselves to racing on flat pavement better than others. But any car will roll if you position it at the top of a hill and release the brake. Likewise, practically any RC airplane can be used for slope soaring. It may just require a slightly different setup than what you’d normally use for open field flight.

It turns out the Bixler 2, my first and so far only RC airplane, makes a darned good slope soarer. I discovered this when I couldn’t find a good place to fly. I finally wound up at the cliffs above Hapuna Beach where a moderate on-shore wind was blowing. The cliffs make a decent slope, and the almost completely laminar on-shore wind make for wonderful flying conditions. I wound up flying for more than half an hour, and only had to use my motor a couple of times to correct my rookie mistakes. When I put the battery on the charger afterward, I was amazed to see it top off with only 330mAh of charge. It’s a 2200mAh battery. I could’ve gone for hours.

When I got my plane, I felt a little dirty – like I’d stuck a motor on a sailboat or put a propeller on a kite. I should’ve known it wouldn’t work out like that. Instead, I found a way to make the airplane fit right along with everything else. It doesn’t matter if it’s kites, boats, or airplanes. It’s all about the wind. It’s always about the wind.

– Tom

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