Updated November 2007

For ALL MODS and AD's see under "Mods and Safety Issues", or click here

The Sagitta (arrow) was the first - and last- single seat standard class design from Holland. Piet Alsema used three years planning and research before the first prototype flew on the 4th of July 1960. Even today the glider looks slick with its slender all-wood fuselage with raked fin and rudder, long pointed nose and sliding blown canopy which provides excellent all-round visibility. Tailplane and elevators are completely wood and consist of two separate pieces connected together with male/female spar and one vertical centre pin. The prototype had tailplanes that could be folded upwards for transportation.

The relatively small wheel is fitted with a drum brake, activated by a lever on the control stick. The two piece wing has a single spar made of spruce and about 25% of the wing is covered by fabric. The ailerons are plain wood and the uniquely constructed airbrakes open both from the upper and lower wing surfaces. The fuselage is of a relatively light construction, while the wings with their extremely strong spruce spars and wooden ailerons are quite heavy constructed.

Original data:
Note: Vne has been tested up to 300 km/h (162 knots) but was later lowered significantly in most countries, and empty weight increased caused by several important safety modifications.
Note 2: according to Louis van Rijn tests have been flown up to 360 km/h (194 kts).

The Super Sagitta 17 meter version (only one built) features a larger rudder and a one-piece tailplane (which rigs like the Standard Libelle). It has a trim surface that connects automatically. The Schempp Hirth airbrakes are built in from the factory.

Note about the span: all serie produced Sagittas are 14.74 meter. This is caused by the use of a "flat" tip element; originally it was round on the prototype.

Some thoughts about the technical causes of quite a few accidents.
Kindly submitted by Louis van Rijn. More to follow in the future!.

After a while, when practical flight results came available, it became evident that the Sagitta didn't weigh up to its promises. So What exactly was the cause for the disappointment in aerodynamic characteristics, especially the stall characteristics in slow turns? This was a typical cause for agressive spinning with often fatal results.
The answer lays in the design of the wing profiles. Louis van Rijn explains:
Even though the Ka-6 and the Sagitta share the same wing profile at the root, they do differ at the tip. The Ka-6 ends up in the old Joukovsky, while the Sagitta has NACA-4412 (or 4415) at the wing tips. It is obvious that at low Reynolds numbers the NACA profile has more drag than the Joukovsky profile. Reynolds numbers are an expression of the wing chord x speed, divided by viscosity. The Reynolds numbers for Ka-6 and Sagitta are around 0.5 to 0.7 E+6. Also the CI-Max is lower in comparison with Joukovsky.
The idea of changing wing profile towards the wing tip, in stead of just changing angle of attack appears to be right. It is used in many modern sailplane designs these days. However, to do it right one needs to utilise a profile with a broad variation in angle of attack; it should stall significantly later than the profile at the wing root. NACA-4415 does not have these characteristics at all. On the other hand, we don't think Piet Alsema had this kind of information at hand at that time...