THE SCHOOLGLIDER SG-38

by Jan Scott

 

We are seeing a growing Interest in primary type gliders, and thanks to our good friend Bjarne Reter, who sent us a lot of material from Norway, we can bring you the following Information on the best of them all, the SG-38. Between 8 and 9000 that 's right, THOUSAND were built in several countries in a ten-year period after 1938. The glider evolved from earlier German primary types like Zogling and Grunau 9, and was designed by order of the German Government in 1938 to provide a standard training machine for the Youth Flying Corps. It was a sturdy, safe and well designed glider, somewhat heavier and with a slightly steeper glide angle than its forerunners. The most noticeable improvements were hydraulic shock absorbers, parallel rudder pedal movement, provisions for trim weights fore and aft, and a screw jack atop the A-frame that was used when the aircraft was put away to unload the flying wires. This jack also expedited assembly and dis-assembly as all the wires could be slackened and disconnected without disturbing the turnbuckles. 

A large horizontal stabiliser and a small elevator surface with limited up travel made it almost Impossible to stall the glider accidentally, and landings could be made, usually without damage, with the stick all the way back during the glide. 

Bungee launches were used most of the time in Germany. After the student had learned to balance the glider with the ailerons, while facing into the wind, level ground "Rutsches" were made; short duration sIing-shots with insufficient speed to become airborne. After the student became more proficient, higher launch velocities were provided, to allow short flights. Later he would advance to hillside launches and finally winch tows. 

Your editor was trained in a SchulgIeiter 38 in Norway in 1948-49. The methods used there were quite different, and I will recap it here, since the procedures were safe and efficient, and can easily be used in many parts of this country. 

Lacking suitable flying fields, almost all glider training was conducted on frozen lakes during the winter. I signed up for one of the first training courses offered after WW II, and along with four others, whom I knew from many glider model contests, headed for the training site in the pre-dawn December darkness. In a barn near the shore of Oyern Lake north of Oslo, was a brand new dismantled SG-38. We stomped through the deep snow, and carried the surprisingly light pieces with their tangle of wires out onto the Ice. Instructor Haydu directed the assembly and rigging which took about one hour.

 

 

By now it was daylight, overcast and a light snow was falling, covering the ice with a thin layer of dry snow. The wind was calm, so no aileron balance training was possible. A small 1930 Ford pick-up was brought forth and a 1000ft steel cable attached to the rear bumper. We watched the preparations with a mixture of fear and excitement. Haydu produced a large yellow and black flag and explained: "We will tow you around in a great circle on the ice". You will steer the glider behind the car and try to keep the wings level. You will not have enough speed to fly initially. When you can control the glider on the ice, we will give you more speed. When I hold the flag up, you may climb, when I hold it out, maintain your altitude, and when I hold it down, land! If I wave the flag, -release immediately'' (handy if the truck went through the ice). 

Initially I made Dollar signs on the snow-covered ice surface; the straight lines made by the wheels of the truck, and the S-pattern made by the glider as I tried to keep it on course. The circular pattern covered about two miles, and after a couple of rounds, I was able to keep the glider straight. There, finally, the flag came up! The speed increased, and the tiny snowflakes felt like needles in my face. I pulled back, and the noise from the skid was replaced by a soft whisper. It was a feeling that has never been topped later in my soaring career! I'M FLYING! Haydu was watching from the truck bed. Too soon he held the flag out; that's high enough! So I learned to fly about two feet off the ice going around in great circles for about fifteen minutes. Was it cold? Have no idea; - I was much too excited to notice! Tried to ignore the flag and go higher a couple of times, but the truck just slowed a little and lowered me back down. 

A couple of weeks later, my disobedient devil surfaced again. We had moved to the larger and more remote Stelnsfjord, and rented a cabin on an island about five miles from the shore where the gliders were kept. It was Friday night, dark and cold and we wanted to take the glider in tow out to the island. Wing walking would have taken more than an hour, so the towrope was laid out, I was strapped in, and told to stay on the ice and follow the taillight. 

Away from the shore it was very dark. The Ice was white and contrasted with the many small islands, which stood out black against the starlit sky. After steering behind that red taillight for about halt a mile I could stand It no longer and pulled back gently. The SG-38 rose slowly to about 400 feet, where I levelled off and enjoyed the view. FANTASTIC! I could see the lights from the truck on the ice below, it was moving along steadily; did they know that their student was up here? The night air was perfectly calm and I could barely see the islands slipping by underneath. As our destination loomed ahead five minutes later, I left my lofty wonderland and landed, ever so carefully, still attached to the towline. 

Afterwards, when the glider was secured in a cluster of trees, Haydu smiled knowingly, but did not say anything and neither did I.

Pilots trained on primaries developed a myriad of bad habits that were not discovered until they flew with an experienced instructor in a two-seater. On the positive side, their self-confidence WAS strong, having been solo from their very first flight. Flying time was logged in seconds; my total time when I received my 'B' was 28 minutes and 35 seconds, and that took 47 flights and 3 years of hard work to accomplish. I later owned a SG-38 which I used for club training. As the instructor traditionally made the first and last flight of the day, I ended up with nearly 1000 flights in the primary.

 

Here are the original German specification for the SG-38:

 

The Schoolglider 38,

Span

10.41 m

Length

6.28 m

Height

2.43 m

Max Payload

90 kg

Maximum Towing Speed

60 km/h

 

The wings have two main spars of the I-beam type with 1.5mm plywood webbing. 

The D-tube is 1mm plywood, additional stiffening is provided through five diagonal braces between the spars. Self-locking hook brackets attach the wings to the fuselage. The flying and landing wires are properly adjusted when the dihedral is approximately 14mm per meter and the screwjack is about 15 mm from the top. The bottom of both spars should be parallel from the root to the inboard end of the ailerons. 

The tall truss is bolted to the A-frame with two quick disconnect bolts, and is braced against side loads through four wires that attaches to the top and bottom of each wing. Horizontal and vertical tail surfaces can be adjusted to exact symmetry through these four wires 

The horizontal stabiliser has a negative angle of incidence of 6.5 degrees when the main wing chord is level. All control surfaces must be adjusted for proper travel. Control cables should he painted red at the point where they are to be disconnected during aircraft derigging. 

Aileron movement: 165-175mm up, 105-115mm down. Make sure that the stick is in the centre when the ailerons are neutral. The elevators are only limited in UP; they should be 130-140mm from neutral when the stick is fully back. Rudder travel Is 265-275 mm, measured at the bottom aft corner of the rudder. Larger rudder travel could enable the glider to spin. 

A seat belt with shoulder harness is mandatory. There are two brackets on each side of the nose where steel trim-weights can he installed, and two similar brackets on the rear portion of the A-frame. CG can be measured tom the leading edge of the wing (Datum), and should Iie between 400 and 480mm with the pilot in the seat. A two piece "egg-shell" can be attached to the A-frame to enclose the cockpit. Your editor has flown with these, and found little or no improvement in performance.

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