Ideas for L/D meter

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Here's a couple of simple ideas for building a true L/D meter (or "Sweet Spot Finder"©® :)
See the picture.

The mechanical one consists of a disk and a vane rotating independently on an axis. The light disk, uniform otherwise, is misbalanced by means of embedded lead weight, so it maintains the same orientation relative to horizon. The vane is a light thin plate pointing in the relative wind direction. The angle between the vane and the level is the glide angle.

The electronic one consists simply of a balanced vane with an electronic level sensor mounted on it. Such electronic levels are readily available (e.g. this or this) and the sensor inside is small enough to be mounted on a vane of reasonable size. The readout of the sensor is the glide angle.

Such an L/D meter can be made the size of an altimeter and be mounted on a belly camera mount, far enough from the body to be in clean air. The electronic model can feedback the glide ratio as beeps of varying frequency in earpiece.

Unlike GPS, L/D meter will show the true glide ratio independent of the winds, and provide instant feedback to the pilot. Also, the disk can be used to slice pizza and as a landing gear. ;)

Ideas, anyone? (especially about wiring up the level sensor)

Yuri :)
Android+Wear/iOS/Windows apps:
L/D Vario, Smart Altimeter, Rockdrop Pro, Wingsuit FAP
iOS only: L/D Magic
Windows only: WS Studio

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It might be difficult to remove and remotely mount the display from a commercial electronic level. If you are interested in a relative indication of AOA and don't need precise numbers, it might be worth trying the following:

Mount your wind vane to the shaft of a potentiometer, and use the potentimeter to provide a variable voltage to a bar graph driver IC like the LM3914, which can drive 10 LED's. As the voltage to the 3914 increases, more and more LED's will light. Use a green LED in the center of the display, and other colors on either side. By placing trimmer potentiometers in series and parallel with the windvane pot, you can adjust the thing so that your "sweet spot" AOA coincides with the green LED being lit. Less than $5 for parts at rat shack. Below is a link to the datasheet for the LM3914, which has example circuits.

Getting the windvane far enough away from the disturbed air without it becoming a line magnet might be interesting.


"Once we got to the point where twenty/something's needed a place on the corner that changed the oil in their cars we were doomed . . ."

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