That's what You should know - a short overview:
The SUNNY-design was developed by me at the end of the 80ies. The aim was a little pusherdriven aircraft, impossible to spin with optimal safe stall characteristics as well as a warranty of longlife qualities.After several investigations I found a report (1948) of Westlands Ltd. testpilot Harald Penrose, who recommended a positive staggered tandem configuration, a conversion of a Lysander at this time, to be a very safe design. This general wing-configuration was brought forward by me using a swept back forward wing with vertical fins at the wingtips which join the swept back upper wing with an aft and down rectangular wing. A boxwing was the result.
This configuration, which was developed in various prototypes, gives the SUNNY-design its distinctive look which combines a better short-
wing-efficiency with directional and longitudinal stability. Another
advantage was to install the control surfaces in the down-wing, with spoilers as a part of the vertical fins, which serve as rudders. Due to the positive staggered wings, which represent a kind of an oversized slot, the rear wing with the control surfaces is not affected by low-
speed.Even if the aircraft is flown with the stick full back (with or without throttle) the aircraft stalls unequaled smooth, shows no tendency to drop a wing or to enter a spin. Decreasing speed in a banked turn makes the aircraft just slide a bit to the center without dropping the nose into a spiral dive. In fact you can parachute this aircraft down for hundreds of meters under full control with the stick and pedals and with a rate of descend to about 9 ft/sec while going forward slow.
Sidewind conditions are easy to handle and generally a well trimmed SUNNY-aircraft flies autostable - hands and feet off - also in gusty conditions, just showing a typical light movement of the aircrafts nose to maintain the levelled flightpath.With this simple and easy flight behaviour I could give more safety to the untrained pilot of light aircrafts, often flying just 20 hours a year, but allow the professional to concentrate on his surveying job. On the other hand, the SUNNY is not boring the experienced pilot, but gives him the joy to fly a high manouverable aircraft following his intentions for real fun flights.
The mechanical construction of the SUNNY-Ultralight followed three principles: Make it as easy as possible, use best prooven standard material with qualified tubes (AlMgSI 1, 6061 T6) and make it easy to maintain and to repair. Having built 150 of the Sunny-aircrafts I sold the production 1999. 12 or 13 new Sunnies were built till 2008, then
the Sunny-production was sold to someone in Switzerland - noone knows who has the rights now. Note:I'm not responsibel for any changes which were made or will be made by other manufacturers nor did I intend or support any changes to the design.
Special Notes
I advice any pilot, who buys a used Sunny: Please do not change the mechanical configuration or airfoil-sections or steering-design, although all those changes are simple to do - in its mechanical aspects. But if You do so You might cause really severe problems in stability and control.
Note: This unique craft needs a very special know-how and its superb flying qualities correspond directly with the MTOW, because it has a built-in flexibility which changes the washout like the wing of a hangglider under weight or accelerations. This is a very important safety and steering feature. The best ready to fly mass of my boxwings will be about 230 kg or below, best MTOW about 370 kg.
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A Sunny to print and testfly is found below. Take a stiff cardboard (minimum double of the weight of the usual printer paper), draw the bending lines with a hard pencil, then cut, fold, glue, ballast and have fun - indoor. Take care: This paper-Sunny shows good stability and performance, but this says nothing about steerability by using usual methods!
Below: My planform from 1990 - it is still the same in all Sunnies worldwide - represented also in the Paper-model, which was sent out with the Tandem-Aircraft-Logo in the early 90ies the first time.
Thanks for reading my bad english :-)
