1. Plastikmodellbauclub Nürnberg e.V.

Grumman F5F-1 Skyrocket, 1:48 scratch built without any kit or accessory parts

The G-34 design for a shipboard fighter with a takeoff weight under 10,000 pounds (4,536 kg), presented to the U.S. Navy by Grumman Aircraft Engineering Corporation in 1938, was unlike anything seen before. Fighter planes of the time were typically single-engine biplanes with fabric-covered wings and rudders and featured twin 7.62 mm machine guns. In contrast, the unofficially named "Skyrocket" was all-metal except for the rudders and had two Wright R-1820-40/42 nine-cylinder radial engines of 1,200 hp each, whose propellers rotated in opposite directions, thus not only balancing the respective torque of one engine but also promising high speed and climb performance. A striking feature was the extremely short nose, which provided an excellent view of the landing signal officer and deck. Two Danish 23-mm Madsen guns were provided as armament.

The design was convincing, and a test specimen under the designation XF5F-1 was ordered on June 30, 1938. The first flight on April 1, 1940, was thoroughly positive, but also revealed inadequate cooling of the engines and a main landing gear in need of revision. The modification of the engine cooling system took until July 15, 1941, because the US Navy's modification requests also had to be taken into account: A flatter cockpit canopy and, because of wartime events in Europe, replacement of the Danish machine guns with four domestic cal. .50 (12.7 mm) machine guns, which required a significantly lengthened nose. In addition, there were modifications to the engine cowlings, extended engine nacelles for improved airflow, and spinners for the propellers. This dragged on until January 15, 1942. By this time, Grumman already had several other new orders, including the XF7F Tigercat based on the XF5F, so further test flights and rework of the landing gear were not top priorities. After two landing gear failures on February 3, 1942, and May 18, 1942, and a belly landing on December 11, 1944, the XF5F-1 Skyrocket was removed from the register and later scrapped. Measured flight data: Top speed 383 mph (616.379 km/h), rate of climb 4,000 ft/min (1219.2 m/min).

The model:
In 1993 there was no kit available for the F5F-1 Skyrocket. In such a case, the experienced modeler looked in his "spares box" for usable parts and / or cannibalized other models. Since I didn't find anything useful on my end, that would have meant buying two Monogram F4F Wildcat kits for the propellers alone. But if you are able to build cockpit canopies yourself (without balsa wood blocks), you should be able to do the same for the fuselage and engine nacelles. That's what I thought and decided to make it 100 percent right away to show that it can be done without kit butchery. Sounds difficult, but it wasn't at all. Required some thought and patience, but it was also a lot of fun. To prove that something like this is possible, in the necessary brevity:

Construction stage 1
In the background, the 1:48 scale plan minus the material thickness of the plastic. On the top left the mold for the fuselage made of polyester putty, on the right the molds for the engine nacelles.
Why there are still people today who think you have to carve balsa wood for a mold, I don't know. Nowadays there is polyester putty, to be found in DIY stores at car accessories, which can already be roughly cut to size after mixing with 4% hardener and can be sanded and polished to a high gloss after complete hardening (alternatively I could have used "FIMO" modeling clay, but here you can't apply a second layer if you made a mistake).
Before that, the already finished parts. The plastic was first softened over a toaster and then pulled over the mold in a smooth motion. A parting line drawn on the mold part and a scalpel helped remove the excess. Strips glued to the inside helped join the two parts (see, for example, model T2V-1). Below you can see the center section of the wings, profiled balsa, front and bottom already planked and cutouts for sloping parts to attach the outer wings.

The clear PVC cockpit canopy, not visible here, was made according to the same principle (see also Modeling ABC page C). As far as handling during "toasting" is concerned, two strips fastened with thumbtacks are sufficient for parts that need little deformation; for others, such as the F5F cockpit canopy here, it is better to cut out the horizontal shape from thin plywood with some allowance for the thickness of the PVC material and fasten the clear PVC to it with thumbtacks. While heating over the toaster, turn occasionally until the PVC begins to shine and become limp. Now pull over the mold with even pressure, PVC side down. If you have already attached a "foot" at the bottom when building the mold (material doesn't matter), your hands will have plenty of room to move down when pulling.

Construction stage 2
Building the wings: core balsa, sanded to profile, planked with thin plastic. First the nose section was molded, i.e. plastic, attached to two ledges, softened and placed around the wing nose; cut off excess and attach molded section with super glue. The following parts need to be done quickly, as the wedge-shaped chamfered trailing edges get a thin layer of plastic glue, but the rest of the insides get super glue. The wing tips are clear polystyrene, which saves having to insert the lights separately. Replicating the fabric covering was simple: mark the ribs on the inside and then emboss with a ballpoint pen, mark the rudder outline on the outside and engrave after planking. Real sheet metal joints are very fine lines, so only drawn with a scalpel tip here. That's all to it. Real planking is as tight as a drumhead and does not sag at all like waves.

Construction stage 3:
The photo above shows how the propellers were made (the finished part on the right). For the propeller blades plastic of suitable thickness was carefully softened over the toaster. After a second or two to cool, both ends were pulled apart, twisting them slightly against each other. This not only makes the propeller blade thinner towards the tip, but also gives it the pitch common to all propellers, i.e. the angle of attack is greater at the hub than at the tip (zero there). The shape is marked with a template, cut out, profiled, finished. For the fastening clamps, I found a nail of suitable thickness, slid a piece of pipe over it, softened it over a candle flame, and then pulled it apart until the material was tight against the nail (same procedure for the fixed part of the landing gear). The hub of the propeller was created from an assembly of pieces of tubing pushed into each other to the diameter of the later propeller axis. After the position of the propellers was marked using a template and appropriate holes were drilled, the propeller blades could be aligned and glued. A thin tube with a plug so that it can be rounded off at the front then completes the whole thing- That's all it took, almost child's play, no resin part, no model stripping required.

Construction stage 4
Unfortunately I forgot to take pictures of the engines and engine nacelles. Of course, nowadays you would buy finished resin parts for the motors, but they were not available and besides, I wanted to show that it can be done without. In principle, it's quite simple: First, wrap a thin copper wire strand around a core (in my case, a suitably made sprue rod, tubes would also work, of course). For better handling, make the core a little longer than needed, fix the wrapping with superglue on the back. Then drill a fine hole each for the ignition cable and cut off after painting result. Engine case: pipe material of suitable thickness, closed at the front by a washer. Mark cylinder spacing of 40 degrees each, then align and fasten cylinders. Front gearbox part: drilled through solid material, roughly shaped, attached to a screw by two nuts, and shaped to final shape by drill and sandpaper, where a previously drawn circle was helpful. After removing the screw, narrow the hole to the cross-section of the propeller axis, as in the case of the rear part, by inserting thinner pieces of pipe (the same applies to the propellers, which are not fitted until the end).

The distributor ring was made from a piece of sprue, softened over a candle flame, pulled apart and immediately wrapped around a brush handle (if necessary, glue two halves together). As a guide for the ignition cables, grooves were filed on the back. Ignition are cables copper wire, at the lower end with a pushed on short piece of thin tube material, fixed with superglue. Pushrods likewise parts of a thinly drawn sprue. Paint both before attaching.