Chapter 13
Chapter 13
P-47D Thunderbolt - EI Coleman
Thunderbolt... a name to inspire visions of the ancrent war gods! Strength in abundance... more than enough to do its job, and still be able to absorb the combat punishment of its adversaries.Conceived by Alexander Kartvelli during the summer of 1940, the P-47 was by far the largest and heaviest single-engine fighter developed to that date, and it heralded an entirely new concept in single-seat military aircraft. While space does not permit detailing the fantastic aerial achievements and outstanding record of this machine, suffice to say that every pilot of "Ace" status who flew the Thunderbolt survived the war. Members of the 56th Fighter Group achieved a ratio of 8 victories for every loss, a highly unusual attainment for ANY combat aircraft.
The rugged and powerful lines of the P-47 Thunderbolt are clearly evident in this photo of the author's model. Note CO2 engine and filler fitting inside the cowl.
The P-47 has been published and kitted frequently as a model, but unfortunately, often with glaring errors. Supposedly authentic scale drawings, some claiming "absolute accuracy" have appeared, and yet, comparison with photographs completely discredits the majority of them. In developing our model, we worked from drawings obtained from Model & Allied Publications Ltd., P.O. Box 35, Bridge Street, Hemel Hempstead, Herts HP1 1EE England. After years of collecting photos, articles, and books relating to the P-47, we consider the MAP drawings to be the best scale reference to be found. In our opinion, these drawings are accurate in scale outline, dihedral, and all visible details.
The Jug without covering. Typically, the nose is filled in with sheet balsa, and the tail surfaces are built as light as possible to avoid excessive ballasting weight.
The "razorback" version was selected to be modeled because of personal preference. Even allowing for the fact that "beauty is only in the eye of the beholder", we feel that no more beautiful aircraft ever existed! If our model manages to capture the essence of the original, with its deep belly, distinctive turtleback, and massive yet graceful appearance, we will consider it to be a success. On to the actual construction.
SELECTION OF MATERIALS
The model was designed for outdoor flying under average weather conditions, and materials were selected accordingly. Medium firm wood was used with certain exceptions, such as the wing spars, leading and trailing edges, rear motor peg mounts and front cowling ring, which were made from hard stock. Particular care was taken to keep the rear of the fuselage and tail surfaces light, to minimize the need for nose ballast.
FUSELAGE
The fuselage is constructed in the traditional "half shell" manner. Basic keels are cut from the printed part sheets,glued together, and pinned to the workboard directly over the plan while drying. All bulkheads are cut from 1/16 sheet balsa, and two of each half are required. Cement one set of bulkhead halves in their respective locations along the upper and lower keels. Use a small square block of balsa to check the vertical alignment of each. Allow to dry thoroughly. Meanwhile, cut out two side keels from printed part sheets, which can be assembled directly over the top view drawing. When dry, they may be removed from the board, and one of them installed on the fuselage half shell. The wing base is installed now.
Wide tread of the landing gear shows up well from this angle. As was the prototype, the P-47 is the largest single-engine fighter model in this series.
After drying, lift the assembly from the work board and continue by carefully gluing the second set of bulkhead halves in position and adding the second side keel. Be sure there is no pulling or distortion of either the keels or wings base parts at this point.
Begin installing the fuselage stringers, first giving each a trial installation. Occasionally, a stringer will be found to have a slight "bend" in it and will not follow the contour between bulkheads smoothly. In this event, enlarge bulkhead notches as needed to shift the stringer into alignment. Afterwards the oversize notch may be filled in with scrap wood, if desired. Taking the time to make these small corrections will result in a better final product. As each stringer is installed, its opposite number should be next in place. The object, of course, is to avoid pulling the fuselage out of line, which may occur if more than one stringer is added to one side at a time. Once the stringers are in place, the short keel piece between F-4 and F-5 may be eliminated, and the instrument panel glued on.
Install the 1/16 inch sheet balsa wing saddle pieces as indicated on the side view drawing. Glue on the nose block laminations. Then finish sanding the inner surface of the three front ring laminations before installing. Note that the nose button is removable for winding, but should be a snug fit. The forward position of the fuselage may be filled in between the stringers with soft 1/16 inch sheet. The method is rather tedious, but results in an exceedingly strong assembly. Dead soft scraps of 1/8 balsa are filled in between formers 5 and 7 and the top stringer and keel piece in order to achieve a transition from round turtledeck to the razor-back inverted V at No. 7. The author prefers a black cockpit interior to simulate depth.
WINGS
Cut two each of the wing ribs from 1/32 sheet balsa, except for W-1, which is 1/16 sheet. Pin the printed part trailing edge pieces and the 1/16 square lower spar onto the building board directly over the plan. Install each wing rib, trimming slightly, if required, for a perfect fit. Next, install the printed part leading edge. Note that the trailing edge tips are elevated an extra 3/32 inch to provide wash-out, as a stability aid. Add both upper spars, and the gussets at W-1 for proper dihedral. Carve and sandpaper the leading and edges to final contour.
TAILPLANES
The tail surfaces are constructed from 1/16 inch square balsa strips plus the printed parts, directly over the drawings. When dry, remove from board, and sand edges to a rounded contour.
LANDING GEAR
The main landing gear struts are bent from 1/32 inch diameter music wire, as indicated. These are sandwiched with 1/16 inch hard balsa reinforcement pieces, or sewn with thread, and glued firmly in place. The detailing is best added after the wings are covered with tissue, but will be described here.
Top view of framework displays most all of the construction technique. As with all scale flying models, the order of the day is strength with lightness.
Build up the main struts from balsa which is sanded round then split to permit installation around the landing gear leg wire. Strips of paper are wound and glued on to build up the various areas of different diameters. The landing gear leg covers and doors are thin card stock, with other details of scrap balsa, etc. Again, it is suggested that photos of the real machines be examined by those who may care to add extensive detailing. While it would be possible to construct actual wheel wells, we elected to simply simulate them with black paint. Wheels were built up as shown and mounted in a hand drill to be sanded to shape as if on a lathe.
COVERING
All structure should be carefully sanded to blend the components together and eliminate surface roughness and any slight misalignments. The bulkhead areas between the fuselage stringers may be scalloped with a round sanding stick, for a smoother covering job. The technique used for tissue and paint is described in the J. D. McHard article elsewhere in this book.
CANOPY
The original model canopy was formed over a carved balsa block. The mold should be primered and sandpapered to minimize the grain of the wood. Chart tape can be used for the frame outlines, as can colored tissue paper. Alternatively, the canopy can be suitably masked and the lines painted on.
A duplicate vacuum-formed canopy may be ordered from Sig Mfg. Co., Montezuma, Iowa.
ASSEMBLY
Trial fit the wing panels to be certain of alignment, and if necessary, trim for a perfect fit. When both panels fit properly, glue them in place. Be generous with the adhesive, since the wings must absorb not only flight loads, but the landing-gear shocks as well.
Covering, painting, and finishing are all well detailed in Doug McHard's photo/article in chapter 15. Wings are butt-glued to wing bases in fuselage. With this arrangement, parts may be covered before assembly.
Cut the slot from the rear fuselage to allow the stabilizer to be installed. Check the alignment of the stab carefully, and glue in position. Cut a small piece of 1/16 sheet balsa to serve as a filler behind the stabilizer, cover the stabilizer, cover the exposed edges with appropriate color tissue, and glue in place. Check the fit of the vertical tail, and if satisfactory glue into position.
Add the various remaining details such as antenna masts, landing gear doors, tail wheel details, etc. It is suggested that the antenna wires be left off until test flying has been completed, since they tend to interfere with handling of the model.
Supercharger ducts and outlets may be carved from scrap, or molded with the use of a Mattel Vac-U-Form. As with this P-47, all of the plans in this book could be used four times up for 2 inch scale R/C models.
A simple, yet effective engine can be simulated with Williams Brothers 3/4 inch scale dummy cylinders. These can be cut in half, modified as required, and fastened to the inside cowl face with contact cement.
PROPELLER
Our test model was flown with a 7 inch diameter Kaysun Plastic prop, worked quite well. Our drawing includes a scale type which could be fabricated for display purposes if desired. POWER
We used a single loop of 4mm Pirelli rubber, or two loops of 1/8 inch brown rubber. Heavier models might require additional power, while a very light model might need less. Experimentation seems the only answer to this question.
FLYING
Check model carefully for warped surfaces. If any are detected, the offending part may be held over a steaming teakettle and the warped part twisted the opposite way. Upon cooling the warp should be absent. Check again later, though, as some warps seem to return with changes of temperature or humidity.
Although we are seldom able to find both, we must suggest the traditional tall grass field and calm day for test flying. Assuming the model balances close to the point shown on the side view drawing, try a few gentle hand glides. Remember to release the model smoothly, and not too fast, in a slight nose down attitude. The addition of ballast to the nose (most likely) or tail should correct any stalling or diving tendencies. If the model persists in "falling off on one wing," add a small lump of clay ballast to the opposite wing.
When the glide appears satisfactory, try a few turns in the rubber motor. The flight path should be smooth, with no strong tendencies in any direction. If stalling under power occurs, add a downthrust shim at the top of the thrust button. If the flight circle is too tight, or there is insufficient turn, correct with a side thrust adjustment shim. More turns are added to the rubber motor, and any needed readjustments performed. Sometimes a little bit of tail surface "tweaking" can be helpful, but should not be overdone. When all is in order, stretch wind with a mechanical winder for longest flights.