Großkinsky - Variable-Camberflap Ring, 80 mm - for Nimbus 4DM - Sale
I'm not sure how I ended up with this extra ring, but I don't need it. It is designed for use on a standard 80 mm Winter W-6423 airspeed indicator (or similar) in knots. A bezel ring is not included. A set like this normally sells for $170. I am selling it for $50. 

Application
As is generally known, wing load and, in turn, the optimum flap positions for the varios speed ranges of a variable-flap glider changes with take-of weight.  Until now, selecting the right flap position has involved using special tables carried on board or observing a confusingly large number of marks on the airspeed indicator.  The new adjustable ring for airspeed indicators makes these complicated methods things of the past.

Features
As the illustration shows, the ring has a double scale for aircraft weight "G": and wing loading "G/F".  Four arrows can also be seen, showing the corresponding angles for the flap positions.  The number of arrows depends on the number of flap positions for the type of glider in question.  Like the MacCready ring of the variometer, the rotatable ring is simply push-fitted onto the airspeed indicator.

Use
One the take-off weight has been calculated by adding the empty weight of the aircraft, the weight of the pilot and the weight of any water ballast on board, the "G" scale is simply turned until this figure is aligned with the 0 mark on the airspeed indicator.  The arrows on the ring now automatically show the correct flap positions on the airspeed indicator scale.  Furthermore, the correct wing load for the take-off weight can be read from the "G/F" scale and entered in an electronic variometer or flight computer, if fitted.  If wing load changes in the course of the flight, due to a reduction in ballast, for example, the ring need only be turned back to the new flying weight, and immediately, the arrows show the new, flight-dependent flap positions.  The ring is calibrated for a standard preset acceleration of 1 g.  If values as high as 1.2 g should occur, as they do in high-performance competition gliding, a second ring with the appropriate values can be fitted during the flight, or changed as required.  If the  Großkinsky ring is not ordered along with a new airspeed indicator, please send us the airspeed indicator and state the type of aircraft in which it is installed, because the scales vary from model to model.  Only the 6 FMS 4 or 7 FMS 4 series airspeed indicators with 510° scales are suitable.
Note: Airspeed indicator not included.

If the  Großkinsky ring is not ordered along with a new airspeed indicator, please send us a digital photo of the airspeed indicator and state the type of aircraft in which it is installed, because the scales vary from model to model.