Chapter 3

 

Chapter 3

Vought F4U Corsair - Frank Scott

The slip-stream howling through the wing root intakes caused the Japanese to call it "Whistling Death." Its unusual shape gave others to call it the "Bent Wing Bird," and its lineage of fine shipboard ancestors lent it the name... Corsair.

First flown in 1940, the F4U Corsair was to become one of the most versatile and effective fighter aircraft of the Second World War, and production was therefore continued for eleven years. The airplane's trademark, its wing, was shaped thus to provide an aerodynamic-ally clean fuselage/wing juncture and a more sturdy landing gear. The large propeller was turned by a Pratt & Whitney R-2800, which was the largest engine then available. This engine was eventually developed to deliver some 2,700 horsepower.


Taking the extra trouble to include the retractable landing gear covers in open position adds greatly to the realism of a model.
Taking the extra trouble to include the retractable landing gear covers in open position adds greatly to the realism of a model.
 

Besides its obvious, and highly successful career as a fighter, the Corsair became an excellent dive bomber, in which role up to 4,000 pounds of bombs were carried. Having no dive brakes, dive bombing F4U (and later AU-1) pilots checked their plunge by simply partially extending the landing gear.

The structure too, was unusual, as the fuselage employed an unusually smooth spot-welded skin (in lieu of rivets), and many Corsair stabilizers were of "Metallic," which was an aluminum-faced sandwich with a core of balsa wood ... yet portions of the outer wing were fabric covered!


Structure of the Corsair is not complicated, but is a little tedious to complete. As usual, it is important that the tail surfaces be kept as light as possible. Note webbed main spar in wing.
Structure of the Corsair is not complicated, but is a little tedious to complete. As usual, it is important that the tail surfaces be kept as light as possible. Note webbed main spar in wing.
 

As a model subject, the Corsair is bound to raise a few eyebrows, and yet in truth, it is a better free flight choice than it might at first seem. The proportions, with the exception of the rather small horizontal stabilizer, are very good. Our model of the Corsair, while a little more difficult than the usual fighter-type rubber scale ship, does involve several procedures that may differ somewhat from tradition. For this reason then, we suggest that the following construction schedule be followed:

The wing is begun by fabricating the main spar. This part consists of a 1/16 inch sheet balsa center section with built up outer panel spars. A spar drawing is provided for your convenience on the plan. When this part may be handled, the center section ribs, R-1 through R-4, are set in place, followed by the center leading and trailing edges. Note that in order to simulate the Corsair's distinctive air scoops, the leading edge is cut away. Strength is maintained in this area by the sheet doublers behind the leading edge.


Worm
Worm's eye view of Frank's Corsair model reveals the typical military two-tone paint job, the spoked wheels, insignia location, and recognition lights. Famous gull-wing configuration permitted larger propeller without long, ungainly landing gear struts.
 

The wing is next propped up so that one outer panel may be pinned flat to the plan, and thus completed in the usual manner. The opposite wing will follow suit. Note that the leading edge spar is drawn extra deep. This allows the leading edge to be pinned directly to the plan without any shims. The extra material is easily trimmed away later, to conform to the Clark Y airfoil. When fitting the wing tips, note that the inboard end of the tip butts up with the lower portion of the end rib, while the very tip is raised to conform to the upper surface of the wing. The wing structure will be completed with the addition of the landing gear mounts, wing intake fairings, wing root sheeting and the various gussets. After sanding and installing the wire landing gear struts, the wing is ready for covering.

The fuselage is of familiar half-shell construction, using keels laminated from 1/16 inch square balsa... except that the fuselage is divided along the horizontal, rather than vertical plane. Thus, the top of the fuselage is assembled over the top view of the plan, and when the top is complete, the lower formers are added.


Minor adjustments in the bulkhead slots may be necessary in order to obtain perfectly straight stringer alignment, but the results are worth the trouble.
Minor adjustments in the bulkhead slots may be necessary in order to obtain perfectly straight stringer alignment, but the results are worth the trouble.
 

Adding the wing saddle pieces will ready the fuselage for mating with the wing. Subsequently, the remaining formers, keel, cowling pieces and stringers will complete the fuselage structure.

The cowling rings are glued together, cross-grain for strength, while the nose is filled in with sheet balsa in the interest of strength, balance, and appearance.

The nose plug may be produced by laminating discs, cross-grain of course, and sanding to final shape. Or alternately, a small model rocket nose cone may be employed. In either case, drill the nose plug to accept the Peck-Polymers thrust bushing. If desired, a dummy engine may be produced by gluing cylinders to the rear disc of the nose plug, N-5. Magnetos carved from scrap are secured to the "crankcase" portion of the nose plug. The installation of a Kaysun 7 inch propeller on its shaft, plus a couple of small washers, will complete the front end.

Vought F4U Corsair plan. Outerzone planID:747
Vought F4U Corsair plan. Outerzone planID:747

 

Turning our attention in the other direction, the tail surfaces are simple, flat strip structures. Careful sanding of these will afford a good savings of weight. Note that the same sheet pieces which locate the tailplane also serve to secure the rear motor peg. The wire tail skid is secured to the upper keel and supported by a balsa brace located between the horizontal keels. Motor access is then afforded through the copious tail wheel well.

The canopy is easily shaped using a Mattel Vac-U-Form toy, and a balsa block form. This form should be carefully shaped, smoothed and sealed, as any imperfections will be faithfully reproduced. The main wheels are laminated from 1/8 inch sheet balsa. As with the cowling, the laminations are cross-grained. The disc forms the back side of the wheel and the axle bearing is either a length of aluminum tubing or a cut down Peck-Polymers thrust bushing. After sanding to shape, the wheel thus formed is placed on its axle and secured with a small washer soldered to the axle. It is necessary that the remaining axle end be trimmed closely to allow the card wheel cover, cut away so as to simulate spokes, to be glued in place over the open face of the wheel.


Corsair plan, detail.
Corsair plan, detail.
 

With the wing and fuselage covered, the covered stabilizer is simply slipped into position in its slot, while the fin is cemented to the upper keel.

The entire model is given one or two coats of thinned, plasticized clear dope (we thin our dope about 50-50, adding 10 drops of tricresyl phosphate per ounce). Color was applied by spraying matte model railroad paints, very lightly, using an airbrush. As an alternative, suitably colored tissue may be used to cover the model. However, we feel that the resulting translucency is inappropriate to a fighter of this era.

As this is a flying model, we now turn our attention to the necessities of flight. While our model was powered by six strands of 1/8 inch rubber, this airplane may easily be adapted to use the Brown CO2 engine. The hole in the nose bulkhead is of ample size to permit a tray-like structure, incorporating mounts for the engine, CO2 tank and filler valve, to be easily inserted interchangeably with the rubber model nose block.


Corsair model in flight.
Corsair model in flight.
 

Regardless of power model chosen, flight adjustments will be of a similar nature. Begin by establishing the balance point as shown on the plans. Bits of modeling clay can be stuck inside the nose bulkhead or tail wheel well as needed to achieve balance and yet not detract from appearance. With the model correctly balanced, the next step is to gently hand glide it, during a calm day, over the legendary but usually unavailable tall grass. The glide may then be trimmed by bending the trailing edge of the stabilizer up or down as needed. (There, now you know what that wide trailing edge is for!) Likewise, turns may be dealt with by deflecting the trailing edge of the fin.

These few procedures should take care of the glide, but before winding the motor, place a 3/32 inch thick shim behind the upper left portion of the nose block in order to achieve a bit of right and down thrust so as to prevent zooming turns into the ground. As the turns wound into the motor are increased, it will be necessary to change the thrust line accordingly. Though this Corsair will R.O.G. very well, we encourage hand launches, due to the vulnerable nature of the landing gear doors and such details.


Complete underside view of paint, markings, panel lines, and insignia.  Ship is decorated in the colors of the Royal New Zealand Air Force.
Complete underside view of paint, markings, panel lines, and insignia. Ship is decorated in the colors of the Royal New Zealand Air Force.
 

REFERENCES

Aircraft in Profile Vol. 47, Vought F4U-1 Corsair. Vol. 150, F4U-4 to F4U-7 Corsair. Doubleday & Company, Inc. Garden City, New York.

Famous Fighters of the Second World War, Vol.2. William Green, Hanover House, New York.

Warplanes of the Second World War, Fighters. Vol.4 William Green, MacDonald & Co. London, England.

American Aircraft Modeler Magazine. October, 1968, P.P. 38B and C. 733 15th Street, N.W. Washington, District of Columbia, 20005.

Scale Plastic Kits:

Frog Kit No. F243F 1/72 Scale "Chance Vought Corsair". Revell Kit No. H-278 1/32 Scale "Corsair F4U-1" .

 
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