Saturday, August 4th, 2012 07:34 am GMT -7 Saturday, August 4th, 2012 07:34 am GMT -7Saturday, August 4th, 2012 07:34 am GMT -7
car speedometer - cruise control - 55 mph driving speed

How fast should you fly your RC model airplane?




Vapor Tale

I have a Parkzone Vapor that I got when the Vapor craze started. That was the time about two years ago when they were really popular. It is a great design, and the popularity is well-deserved. In fact, I have had to retire my Vapor simply because it is so beat up. I have flown it many times.

When we fly indoors around here, helicopters and airplanes take turns. When it is time for airplanes to fly, it is not unusual to see a dozen take to the air all at once. When the Vapors were really popular, easily half of those were Vapors.

When you have half a dozen Vapors flying around, an obvious problem is telling them apart. You could always count on somebody getting confused and “flying” the wrong model. But that is an entirely different issue from what I want to talk about right now.

You see, I started noticing something really odd. Even though all the Vapors were taking off at the same time, mine always landed last. This was before all the third party batteries hit the market, so I know all the Vapors were identical.

Watching them fly around, I could not see any difference between any of them. We were all doing aerobatic maneuvers, touch-and-gos, etc. So what was so different about my Vapor?

Fly The Wing

What I realized is that I was flying my Vapor slower than the others. It was still fast enough to do all the maneuvers that I wanted to do, but I just was not zipping around the air.

If you study airplane wings and airfoils, you will learn that wings are most efficient at an angle of attack of about four degrees. This is where their lift to drag ratio is the highest, a key measure of airplane efficiency.

Take zero degrees angle of attack to be when the airplane fuselage is horizontal (close enough for our purposes). For a thin airfoil like the Vapor, the stall angle will be close to 10 degrees. So then the cruise angle of attack will be about halfway those two.

Full-size airplanes care a great deal going places. They fly at the cruise airspeed to get maximum range (note: I believe I said endurance in the video by mistake). A model airplane usually does not care about getting the best range. But we do care about how long we get to fly.

Flying Like an Airplane

Too often, I see model airplanes tearing through the sky. They look more like rockets than airplanes. For the use they make of the wing, it might as well not be there!

There is a lot of beauty in watching an airplane or a bird fly. If you want your model airplane to fly like it was designed to, fly it like a model airplane and not a rocket. Slow it down and fly the wing.

You might realize that there is a whole set of flight maneuvers that are now possible to perform using your model airplane. You might enjoy flying it more, too.

Finding the Sweet Spot

Sometimes folks tell me that they just fly their models at 75% throttle. But the meaning of any intermediate throttle setting is just an artifact of the transmitter and speed control programming. 75% throttle really does not mean anything.

Try different throttle settings, looking for the sweet spot. You are looking for a nice intermediate airspeed.

If you want to do a loop, and you need to dive before you start it, I see nothing wrong with that. In fact, that may be a good sign that your flying speed is just about right.

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