While working at the Darmstadt Akafleig, Klaus Holighaus was a member of a team (including Gerhard Waibel, Wolf Lemke and Walter Schneider) on the ground breaking D-36 project.  This aircraft led directly to the Schleicher AS-W 12 (Waibel's first project with Schleicher).  Holinghaus used this experience later to develop the Cirrus, his first full aircraft project at Schempp-Hirth, but the design philosophy was completely different.  The D-36 (and subsequent AS-W 12) had a thin wing, flaps, a tail chute in lieu of dive brakes (AS-W 12 only), extremely supine seating and was built on a male (internal) mold.

In November of 1965, Klaus Holighaus joined Schempp-Hirth.  Klaus Holinghaus' first job at Schempp-Hirth was to convert the SH-1 (originally the Austria designed by Rudi Kunz for the Austrian Aero Club) into an open class ship.  Klaus added 2 meters to the wing, increased the tail area by 50%, lengthened the nose a little and the new sailplane was designated the SHK.  It's  believed the K is for Klaus, although it could be for Kircheim (the city in which Schempp-Hirth is located).

He immediately began the design and construction of the Cirrus V-1.   (In fact, his PhD paper at the Technical University of Darmstadt consisted of the design and calculations of this sailplane.)  The concept of the Cirrus relied on a thicker airfoil and the use of water ballast to improve the run, a more upright seat, the use of PCV foam instead of balsa as a core material and the use of a female mold (the adapted technique by all manufacturers).  Evidently his work was quickly recognized, since by January, 1972 he had assumed the administration of the factory and in 1977 became the proprietor.

Although Schempp-Hirth had made extensive use of fiberglass in the Standard Austria and SHK, the Cirrus was the first all-fiberglass machine they put into production; the only exceptions are the foam cores used to make the sandwich material for the wing skins and the fuselage bulkheads, and the internal steel frame in the fuselage. The unique internal tubular-steel frame ties the wings, pilot seat, and landing gear together. This frame is bolted to the fiberglass shell, and facilitates both the initial construction and any repair, since the highly stressed structure is steel.

The 17.8 meter wings illustrate an interesting compromise between goals of efficient thermalling and high speed interthermal flights, intended to meet the requirements for soaring in central Europe. A rather thick Wortmann airfoil (FX 66-196/161) is used which yields low wing drag over a wide range of speeds, very gentle stall characteristics, and provides excellent thermalling performance without having to increase pilot workload with flaps. The slight disadvantage in high speed cruise from the thicker airfoil is offset by using ballast. In addition to very effective top-and-bottom spoilers, the Cirrus has a substantial drogue chute built into a little box on the bottom of the rudder. The result was a machine with an advertised best L/D of 44:1, excellent thermalling characteristics, and superb short field capability.

With the clarity of hindsight, it appears the Cirrus is to a significant degree "overbuilt". In the sixties, it wasn’t clear just how strong these composites were and how long they would last - accordingly, the design was rather conservative. The wing was static tested to 15 G’s, and very extensive fatigue tests were conducted to simulate a life of 30 years (about 9,000 flying hours). Good thing, now that several of us are flying Cirruses more than 30years old!! The testing included a total of 6.5 million stress cycles imposed on the wing, running through load factors of +5.75 to -3.45 G units. After the fatigue tests, a static test at temperatures up to 129^o F under design load conditions corresponding to a gust speed of about 140 mph. Three decades of flying appear to vindicate the robustness of the machine.

The first prototype (see picture) is the only Cirrus with an all-flying V-tail, reflecting its design origins in the Austria.  Actually, Schempp-Hirth built two prototype fuselages which flew with the same set of wings. Both had the same German registration number (D-9406) but one had the V-tail (the V-1) and the other had the conventional tail (the Cirrus B?  See below. . .) which went into production. Schempp-Hirth switched to the conventional tail for marketing reasons after Dick Johnson "jumped" out of the Standard Austria, and it was felt that a conventional tail would sell better in the US, perceived as a major market.

The Cirrus "B", or Long Span, Cirrus Mystery

Several of the Cirruses in the US are registered with the FAA as "Cirrus B" models.  In the 1969 US National competition, George Moffatt's Cirrus, No. 23, was referred to by the SSA as a Cirrus B (different from the other Cirruses entered in the contest).  It is well known that George Moffatt had himself extended the wingtips of No. 23 to 18.8 meters; there is a videotape of him sawing off the wingtips himself, and gluing longer tips onto the wing! 

H.A. Torode reports in a 1971 flight test (funded by the UK Ministry of Aviation) of Cirrus No. 21 “…has only one non-standard feature, which consists of an extension of the wing span by 1 metre to 18.7 metres (62.8 feet).  This modification, designated Cirrus B, has been incorporated by the Schempp-Hirth Company in an attempt to improve the low speed performance of the sailplane.”   

However, in  a personal conversation with Tilo Holighaus at one of the Soaring Society of America conventions (late nineties), he related to the author that the "Cirrus B" was the conventionally tailed, production model (vice the V-tailed prototype) and that the factory had never provided or approved any wing extension modifications. 

To make matters still more confusing, Herr Helmut Trieber of  Schempp-Hirth wrote the author on May 3, 2001:
      “In the Data Sheet Nor [sic] 265 only the  serial-number 16 is designated with "Cirrus B" with an extended wingspan of 18,34 m. This is an extension of the wingspan of 0.6 m and not 1 m as you have mentioned below. This modification of the wingspan was done according drawing No 50.002-B, Cirrus B, Flügelspitze (wing tip). No official documentation is available for a wingspan extension of 1 m.” (No. 16 was last known to be in Germany (in 1998), designated D-9422, owned by one Herr Badewitz and flying in Bayeruth. )

Finally, in the spring of 2001, the wreckage of No. 23 was inspected at McClean Aviation in York, UK.  It was measured carefully and discovered to be 18.56M in span, significantly more than the 18.34M specified for the Cirrus B by Schempp-Hirth's own drawings.  Curiously, No. 23 has a decorative written designation "Open Cirrus 18.8" painted on the side of the cockpit!

So at this writing, it would appear that there exists (or did at one time) three "long span" Cirruses, (Nos. 4, 21, and 23), one 18.34 meter Cirrus (No. 16), and ca. 166 17.8 meter Cirruses.  It is far from clear which, if any, are correctly labeled the so-called "Cirrus B".

Between 1967 and 1977, Schempp-Hirth produced a total of 183 Cirruses, including the prototype. Of these, 29 are believed to have been produced in Yugoslavia under license by the Vazduhoplovno Tehnicki Centar in Vrsac, Yugoslavia and are often referred to as the "VTC" or the "Yugoslavian variant". (None of the Cirruses imported into North America was a VTC.)

References:
    The Schemp-Hirth Website (http://www.Schempp-Hirth.com)
    Selinger, Peter, F., "Segelflugzeuge vom Wolf aum Discus", Motorbuch Verlag Stuttgart (1989)
    Steve Lindenbaum, Atlanta, GA,  Personal Communication (1999)
    Anonymous, "German ATC for Cirrus", SOARING Magazine, February 1969
    Ryan, John, "Cirrus Test Pilot Report, SOARING Magazine, July 1967
    Foley, William F., "The Schempp-Hirth Cirrus, SOARING Magazine, July 1967
    Torode, H.A., "Flight Performance Tests on a Schempp-Hirth Cirrus Sailplane", Cranfield Institute of Technology, Ministry of Aviation Contract K20C4/53/CB20C, 1971