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Chapter 11 - Twin-Engine “Mustang” Fighter

Contrary to general opinion, twin-engine model airplanes do not necessarily require large wing spans. In fact, the smaller variety are rapidly gaining in popularity because of their simple construction, the small flying area required, and the high strength-to-weight ratio. This does not mean, however, that large aircraft models of the multi-engine type have no attraction whatever. The larger models are certainly a great source of enjoyment and their size allows room for considerably more detail than do those of diminutive proportions.

In order to select a model that would appeal to the experienced builder and yet be simple enough for the novice to construct and fly, we have selected a "half-A" engine powered craft which can be flown with any combination of engines from .020 to .074 cubic inch displacement. Both engines need not be of the same power or type. The relatively close location of the engines to each other reduces to a negligible factor the turning tendency caused by uneven power. We have powered our model of the "Twin Mustang" with one Cub .049b engine and one Cub .074" engine. On numerous occasions, the model was flown on either one of these two power plants with complete success. This could not be done with larger planes with wing spans of 30 inches or more without some skillful maneuvering on the part of the flyer.

Scientific   Photo

This is a photograph of the Scientific kit of the "Twin Mustang", designed by the author. This model is the same size as the F-82G described in this chapter but the construction varies somewhat.

Notice that the . coloring is silver with black identification numerals and anti-glare panels. This is the normal day fighter coloring for the F82E. Either black or aluminum dope can be used to  color your model.  The  silver model should not be fitted with a "radome".

On the larger models, the outboard engine is generally started first in order that it may stop first. In this way, the turning tendency caused by the uneven power will force the model away from the flyer and thereby insure taut flight lines. This was no problem on our model. Many twin-engine craft feed from the same fuel tank, usually a pressure type, in order to stop both engines at the same time.

During the testing of our "Twin Mustang model we not only flew on one engine with the remaining engine stopped but actually removed an engine and substituted lead weight to maintain correct balance. Flights were most satisfactory with only one engine installed and operating. This amazing report will be of extreme interest to the young reader who, due to restrictions of allowance or other financial factors, cannot purchase, two engines at once. The possibility of flying with one engine alone will enable the reader to construct this "Twin Mustang" at once and enjoy flying the model with one engine installed. The second engine can be purchased and screwed into place at a later date for some real twin engine enjoyment.

"The Lensman"  Photo

All markings are clearly defined in this photo of our "F-82 Mustang". Numerals are white "Wondur-cal", while control outlines are ruled onto the model with inexpensive draftsman's ruling pen and white ink. Four bladed propellers are merely two standard two bladed types half-lapped together and cemented well. This replica is the F-82G all weather night fighter version, and therefore, sports an all black paint job.

As the standard long-range, high-altitude escort fighter for the United States Air Force, the North American "F-82 Twin Mustang" is the climactic development of a long series of the famous World War II "F-51 Mustang" series. Two standard Mustangs were joined to form this most effective airplane.

Two hundred and fifty of the double-fuselaged airplanes were produced by North American Aviation, Inc. for the Air Force; these embraced three versions of the Twin Mustang which were in service, the F-82E, F82F, and F-82G.

"The   Lensman”   Photo

Our prototype "Twin Mustang" was fitted with elongated landing gear in order to accommodate larger five and one-half inch propellers. Attention should be paid to the fact that radio mast appears only on the right hand fuselage while a directional loop is fitted on the left hand fuselage.   Canopies are standard "Scientific" bubbles.   Spinners are aluminum.

These three models incorporate new features developed since production of an earlier version of the series, the F-82B, the model which on February 28th, 1947 set a non-stop fighter record, flying the 4,968 miles from Honolulu to New York in 14 hours, 31 minutes, and 50 seconds, at an average speed of 341.9 miles per hour.

Versatility of the F-82 makes it adaptable to a wide variety of roles in modern aerial warfare. It can be used as a fighter, a long-range escort, long-range reconnaissance, night fighter, attack bomber, rocket fighter, or interceptor.

With a speed for more than 475 miles an hour, the "Twin Mustang" has a combat range of over 1,600 mile* with full armament. Range can be extended by use of external drop tanks on the wings. Comparison with modern jet fighters shows the F-82 has more than twice the range and takes off in considerably less distance.

Lensman   Photo

At the age of six and one half years old, the author's daughter Carolanne proudly displays the underside of Dad's "Twin Mustang". She is now fourteen years old and the F-82 model is still in good flying condition despite continuous activity and several engine changes. Notice the "radome" between the fuselage, and the engine cylinders protruding from the metal cowls.

Although six .50 caliber machine guns are standard armament, the F-82E also can carry eight additional guns in a special center-section nacelle. Five rocket-launching racks carrying five rockets each give the F-82 a firepower equivalent to a light cruiser's broadside. The plane can also carry 7,200 pounds of bombs, or a photographic nacelle, radar nacelle, rocket gun nacelle, or a 2,000-pound torpedo.

The F-82F and F-82G airplanes are "all-weather," night-fighter versions of the F-82. The center nacelle is utilized for search radar equipment in these models. This is called a "radome."

Air Trails  Photo

Expert model builder Leon Shulman. constructed this five and one-half pound replica of the "Martin Marauder" for Air Trails magazine, a monthly publication for which the author frequently illustrates and describes model aircraft. A model of this size should only be attempted by the experienced builder. The novice should start with a simple model like our "Twin Mustang".

Powered by two 12-cylinder V-1710-G6 engines manufactured by the Allison Division of General Motors, the F-82 utilizes two full-feathering four-bladed Aeroproducts propellers. Each engine generates approximately 2,200 horsepower, enabling the craft to operate efficiently up to 42,200 feet.

A radical departure from the conventional single-fuselage airplane, the "Twin Mustang" is formed by two fuselages joined by the wing and the horizontal stabilizer. With a pilot in each fuselage, it reduces to a minimum the problem of pilot fatigue on ultra-long-range missions. The F-82F and G models carry a radar operator instead of a co-pilot in the right cockpit.

Both engine throttles and both propellers are controllable from either cockpit by manually operated levers. The pilot's cockpit on the left contains the normal flight and engine instruments, while the co-pilot on the right has sufficient instruments for relief and emergency operation.

A simplified cockpit arrangement has been worked out to improve pilot comfort, including a tilting, adjustable seat to reduce fatigue during long flights.

One of the first items to feel the sharp edge of your cutting tools are the twin fuselages.  Trace the top and then side views and cut to outline shape onto soft balsa blocks, as described in previous chapters for carved fuselages. It is advisable to construct both components at the same time in order to insure identical shape. Sand smooth and rout out the interior with a gouge. Be sure to cut the fuselage bottom to fit the wing.

North American Aviation Photo

Of special interest in this photo of the "F-82" are the suttle wing and tail fillets. These can be made with several applications of cement. The "Twin Mustang" started as the P-82; however, all "pursuit" designations were abolished in the Air Force and substituted with "fighter" designations.   Hence,  the "P-82"  became  "F-82."

North American  Aviation  Photo

It is a habit of all successful scale model builders to study all photographs of their subject before and during construction. This photo, for example, contains a wealth of information on such items as tail wheel door, radiator scoop and main landing gear fairing. Door and fairing e«t from thin sheet metal on our model the scoop is carved from soft balsa.

North American Aviation Photo

The deadly armament carried by the "Twin Mustang" is well illustrated in this front view of the full size craft. Three clusters of rockets plus auxiliary fuel tank and chemical tank are only a few of the many varieties of lethal cargo carried by these unusual craft. Note the six gun ports in the leading edge of the wing center section.

Air Trails Photo

Edward Morgan of Nevada is pictured with his six foot model of the "Douglas DC-3 Transport". This replica is powered by .65 engines, the largest class. The craft is complete with seats, passengers and lights. These large crafts are very roomy and can be fitted with an extraordinary amount of details.

The wing is made in three sections in the same manner as described for the wing in Chapter Five. After the sections are complete they can be cemented to each other. Each wing tip should be raised so that it is 1/2" above the work table when the center section is laying flat on the table therefore be sure to tilt the outer panel ribs during construction.

Cement the two fuselages securely to the wing, using plenty of cement. Install any commercial fuel tank into each fuselage, being certain to add the plastic tube extensions and feed line to the tank connections. Cut the plywood bulkheads to shape and cement to the fuselage front. Apply plenty of cement into the inside of the fuselage. Cover the bottom of the fuselage with sheet balsa.

North  American Aviation  Photo

Propeller, canopy and landing gear detail are well displayed in this excellent "F-82" photograph. These craft can be painted all silver with black anti-glare panel on the forward fuselage top if a black plane is not desired. All lettering is made black on all silver aircraft. Note the streamline exhaust stacks which can be reproduced by the meticulous modeller.

With the wing in place, the radiator scoops can now be added. These are carved from soft balsa in the same manner as a fuselage.   Cement in place to the fuselage bottom and fillet well with "Plastic Balsa." Apply several layers of this material. Let dry overnight and sand well until smoothly faired.

Cut the empennage to shape, sand well, and add the control horn to the elevator. Hinge this to the stabilizer in the accepted manner and set aside to dry. Cement the fin and rudder to the fuselage top and mount the stabilizer between the fins. This must be parallel to the wing. Fillet all wing and tail joints with several coats of cement. When dry, apply "Sanding Sealer" to the entire plane in the quantity desired. We applied three coats. Sand well between coats with 3/0 sandpaper.

Paint the plywood bulkheads; while this is drying, bend the two landing struts to shape. Fit these into the grooves in the bulkheads and screw the engines in place. The engines hold the landing gear in place. Connect the plastic fuel feed line to the engine and cut the metal cowl from shim brass, tin can metal, or .007" aluminum sheet. This is held in place on the model with ½" long straight pins forced into the bulkhead.

Air Trails   Photo

This sleek "Douglas B-26 Invader" wears the jet black mantle of the night fighter, similar to our "Twin Mustang" model. Plans for this craft appeared in the Air Trails Model Annual for 1953. Periodicals such as this provide much useful and entertaining information for the model enthusiast.  The Douglas pictured here is of the larger variety twin engine model aircraft.

Propellers are wooden 5-inch type of 3-inch pitch. These are half-lapped together and cemented under pressure to form a four-bladed propeller. Sandpaper the blades to a ⅜" width and reduce the diameter to 4¾". Paint black and then fuel-proof. As an alternate, the craft can be flown with regular 2-bladed, 5"-diameter, 4" pitch propellers. Any commercial lor 1⅛" diameter plastic or aluminum spinners can be used. These are painted red and then fuel-proofed, then fuel-proofed.

Our model duplicates the night-fighter version of the "Twin Mustang" and is, therefore, painted jet black. All lettering is white, while insignia is standard red, white, and blue. Small plastic pilots can be fitted if desired. The transparent plastic bubbles are "Scientific" canopies. These must be trimmed carefully and then cemented to the fuselage top.

The last items to be attached are the bellcrank mount, bellcrank, lead-out control lines, and control line guides. The guides can be made from bent electrical soldering lugs, small screw eyes, or bent wire. Be certain to twist the ends of the lead-out lines as described in previous chapters. Touch up newly cemented areas with fuel proofer.

This 8-ounce craft should be flown on .008" steel control wires. Flying is no different from single-engine craft except that two engines require starting. Try to keep them both running at approximately the same speed before taking off. To hear a twin-engine model flying through the air is a truly unforgettable experience.

A four bladed propeller for the "Twin-Mustang" or the "King Cobra" can be made by joining two standard commercial wood propellers in the manner shown here. Step One illustrates the portion that is to be cut away. This should be carefully marked on each propeller. Step Two shows the proper way to remove the wood from each propeller hub. Be certain to cut a little at one time. Step Three indicates the method of joining the two propellers. These should be trial fitted before the cement is added. Use plenty of the adhesive. Step Four is the final operation and consists of a "C" or cabinet clamp to hold the two components together until the cement dries thoroughly. It is imperative that the blades are at right angles (90°) to each other before the clamp is tightened. Remove the clamp when dry and smear several coats of cement around the joint. Paint the propeller black.

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