KB-5 Triglav III
The tests on KB-1 Triglav were completed and it was obvious that the plane could be improved with systematic modifications. At the time the designers were able to contact foreign designers and pilots and this resulted in a lot of improvements. There was a world wide campaign going on against excessive drag so eventually even the Pitot tube was moved to the nose of the plane. All gaps and notches wre reduced to minimum, the remaining ones being taped over before the flight. The cockpit canopy took the form of a blown plexiglass bubble. |
The monowheel was removed and so were the flaps as the gap between them and the wing was causing a lot of drag. The wavy surface of the wing between ribs was kept to a minimum and wing tips got streamlined wing tips in order to reduce induced drag. The prototype was in fact a reworked KB-1 Triglav. Most modifications
were made on the fuselage by removing everything that was not essential
and by installing a new canopy installed. Wing attachment mode was not
changed. |
Tail surfaces were modified into a V-tail that was unfortunately too heavily built and a counterbalancing weight had to be fitted into the nose. Nevertheless, the plane was 10 kg (22 lbs) lighter than the production version of KB-1 Triglav. The main goal for all these changes was to achieve better glide ratio and indeed it was improved by 2.1 units to 28.4 at 70 km/h (38 kt). Only the prototype KB-5 was built but it was more than an experiment - it showed what could be achieved in a sailplane with precise building. It is a pity that development was not carried on. The plane therefore represented the last phase in a development of a
sailplane with conventional wing section and marked the end of the first
phase in the work of the 'Konstrukcijski biro'. |
| Data | Prototype |
|---|---|
| Wing span | 15.00 m (49 ft 2 1/2 in) |
| Length | 6.83 m (22 ft 6 in) |
| Wing area | 13.52 m2 (145.3 sq ft) |
| Aspect ratio | 17 |
| Dihedral | 4.47o |
| Wing section | Goettingen 549-16%/549, M-6 |
| Empty weight | 166.85 kg (368 lbs) |
| Max weight | 255.00 kg (562 lbs) |
| Wing loading | 19.3 kg/m2 (3.95 lb/sq ft) |
| Best glide ratio | 26 at 69 km/h (37 kt) |
| Min sinking speed | 0.7 m/sec at 65 km/h (2.3 ft/sec at 35 kt) |
