SZ-25 fuselage is nearing completion.
Maanantai 4.4.2016 - Member of Tuesday Club
Tuesday Club has almost finished restoration of a Focke-Wulf Fw 44J Stieglitz fuselage. This elementary trainer was originally used by Finnish Air Force with registration SZ-25 and it will be installed as a gate guardian at Kauhava Airport, where it used to serve. The last items to build were pieces of aluminum cowlings around engine mount. This shiny cowl is now waiting to be painted with the original green tone of ”Stigu” (the nick-name of Stieglizes in Finland). Wings have been ready since before Christmas and they have been delivered to the Finnish Airforce Museum at Tikkakoski to wait for final transportation to Kauhava next autumn.
Building the cowl was a complex and challenging task. Parts at both sides of engine mount are made of two pieces and hinged together. They are attached to engine mount with locking pins. They also have cooling louvres which help in keeping engine temperature down.
The original cowl of SZ-25 was lost at some point of its history, so the new one had to be built from scratch. As a model we had the same parts of Stieglitz SZ-4 obtained from Finnish Airforce Museum. Finnish Air Force Stieglizes were individual enough to prevent SZ-4 cowlings from fitting perfectly on SZ-25. So, we couldn’t just copy but had to shape new cowlings to the individual dimensions of SZ-25. Even so, a model made our work faster.
New cowlings were cut from one millimeter thick aluminum sheet, shaped and edges strengthened according to engine mount dimensions. The top side cowling was easy to do because it is just a curved aluminum sheet.
Sides were more challenging with their louvres and latches. Making louvres started with cutting in an elongated slit. Subsequently, the leading or outer edge of the louvre was formed by forcing this side of slit to protrude out along a correctly shaped block of wood. The inside of louvre was shaped with a fitting piece of aluminum which was riveted onto the trailing edge of slit.
Latches, which secure cowlings to engine mount, were made at the same time. We needed to make eight of them as both parts of one side need two latches. Pieces of aluminum were bended to form bodies with lugs. Lugs were drilled to have holes. Matching locking pins were cut from a metal rod. Small levers were attached to each locking pin for moving it.
Locking pins needed also springs for which there was no suitable commercial ones to be found. Springs were made by twisting 1 mm piano wire tightly around pins. This gave suitable force and length to each spring. With springs on, locking pins were now ready to be attached to cowlings.
Side parts were attached to each other by piano wire hinges. Further, side cowlings were attached to the edges of top side cowling by locking pins. The final adjustment was to see that locking pins held on and opened perfectly.
Meanwhile, Wednesday Club at Finnish Aviation Museum has been refurbishing a Siemens-Halske engine for SZ-25. After engine is finished, it will be installed onto SZ-25:n engine mount, which makes the fuselage ready to be sent to Kauhava.