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Chapter 12 - “Shooting Star” Jet Plane

Jet-propelled scale models are, by far, the most advanced type of control liners. These are also the most complex to construct and much care must be taken in the engine installation. This is so because the heat radiated from these engines must be dissipated before it can harm the fuselage. It is because of this as well as the exceptional flying ability required to handle these craft that the amateur is advised not to attempt this type of model.

If the reader has constructed all the models presented in this volume, or an equal number of similar types, he should be able successfully to complete a jet-powered craft.

The development of safe miniature resonant-type jet engines by Mr. William L. Tenney finally enables the model enthusiast to reproduce virtually all of the world's jet aircraft in model form. These engines burn white gasoline and generate thrust by a succession of rapid explosions. So rapid are these explosions, 230 per second, that the resultant effect is a roar. These engines are called "Dyna-jet" and sell for approximately thirty-five dollars.

The first of the basic requirements that the jet-propelled scale model must meet is that of the fuselage cross-section.

Air Trails Photo

Prize winning "Dyna-jet" powered replica of the "Grumman F9F Panther" was built by Frank Laschek of New Jersey. Major problem of these jet powered models is the elimination of the heat radiated by the engine before it harms the fuselage. Most scale jet models require bulky fuselage to allow an air space around the powerplant.

This must be large enough to accommodate the jet power plant with sufficient air space surrounding it to prevent a charred interior or blistered paint on the exterior. In order to achieve as large an air space as possible, it is advisable to carve the fuselage from a balsa block and hollow to a wall thickness of about 3/16". This has a definite advantage over the formers-and-planking type because the formers must be at least ½" in order to possess the strength to hold the shell in place. This not only hinders the flow of air through the fuselage but also cuts down the distance between the engine combustion chamber and the nearest wood member.

In view of the fact that the jet engine weighs approximately one pound and requires a considerable amount of fuel, it is advisable to construct a fairly large airplane. This probably has already been dictated by the air-space requirement mentioned in the preceding paragraph. The majority of jet-propelled airplane models weigh between 3½ and 6 pounds. A weight of 4½ pounds is deemed desirable from an easy-to-fly standpoint.

Lockheed  Aircraft   Photo

The early "Shooting Stars" were colored pearl grey as this photo shows. Today, the "F-80" is left natural aluminum and identification numerals are black. Note the large wing walk which is colored black. The wing tip fuel tanks as seen here are almost a necessity on the model. One never sees an "F-80" without them, as a matter of fact they have almost become one of the plane's characteristics.

Once these requirements have been met in our design, it will be found that the engine must be located in that portion of the fuselage aft of the intended balance point. The jet tailpipe must protrude from the fuselage rear. It is, therefore, necessary to add a considerable amount of weight in the nose in order to balance the model correctly.

In addition, the controls must not be over-sensitive because these craft fly between seventy-five and one hundred miles an hour. At this speed, the slightest control movement causes erratic flying. Long control horn, short bellcrank third arm, and small elevator area will decrease control sensitivity.

Lockheed  Aircraft   Photo

The after portion of our model fuselage has been enlarged somewhat to allow air to circulate past the jet engine and carry off the heat. This F-80 photo is of interest because of its markings and bubble canopy details. These bubbles can be found at most hobby shops or from Berkelv Model Airplane Co. All plastic bubbles must be trimmed to fit the model fuselage properly.

Aside from these requirements, jet-scale models are no different in construction, flying, or design from any "man-size" model airplane.

When one mentions "jet propulsion", it is inevitable that the "Lockheed Shooting Star" is brought to mind. This is the plane we have selected to be reproduced in model form. Here are a few words about this famous craft before we begin constructing our model. The "Dyna-Jet" engine is manufactured by the Curtiss Automotive Devices Company.

The "F-80 Shooting Star" was the first mass-produced jet aircraft in the U.S. Air Force.   Developed and built by Lockheed Aircraft Corporation, Burbank, California, this veteran fighter was also the first American jet plane to enter combat at the outbreak of war in Korea. It won history's first jet air battle by shooting down the first Russian MIG-15 jet fighter. An "F-80" model has been placed in the Smithsonian Institute to commemorate this historic victory. Again, the "F-80" was the first U.S. jet fighter to be assigned overseas; the first American jet fighter to fly the Atlantic and prove the practicability of long over-water flights; and also the first jet plane to become standard for the U.S. Air Force. From the basic "Shooting Star" design stemmed the "T-33," first USAF jet trainer, and the new highly automatic, all-rocket-armed "F-94C" Starfire all-weather interceptor. Its sleek lines make the "Shooting Star" one of the world's handsomest airplanes. Powered by a General Electric J-33 turbo-jet engine of 4,000 horsepower, the F-80 attains a speed of 550 miles per hour. Gross weight is 11,700 pounds. Six .50 cal. machine guns are fitted in the nose.

As is generally customary, the construction is started with the fuselage. It is advisable to obtain two blocks of wood and join them lightly at the horizontal centerline of the fuselage. Once the fuselage is sawed to shape, carved, and sanded, the two halves are cut apart. Hollow both halves exactly as is shown on the plans and be certain to cut out the air scoops as much as possible. Sand the interior well. Assemble the elevator and stabilizer, add the horn, and then cement the stabilizer to the upper fuselage half. Cement the fin and rudder atop the stabilizer. Set this component aside to dry. The remaining work on the model is virtually all done with the lower fuselage half.

Cut the wing spars, joiners, and ribs to shape, sand well, and assemble in the same fashion as described in Chapter Seven. Before the wing is covered, the bellcrank and landing-gear plywood supports must be fitted and both bell-crank and landing gear installed. These attachments must be secure.   Add the control rod at this time.   The two wing panels can now be covered with sheet balsa. Be certain to bevel the covering as we have in the past. After the wing tips and tip tanks have been fitted, the wing assembly is cemented securely to the fuselage lower half by notching the fuselage as we did for the "King Cobra." Once cemented to the fuselage, the wing should be generously filleted with "Plastic Balsa." While this is setting, the hardwood engine-mount foundation can be firmly "Casein Glued" into the fuselage bottom and filleted with "Plastic Wood."

Curtiss Aeromotive Photo

This "Shooting Star" jet propelled model flew very well when powered by the "Dyna-Jet" reso-jet engine. Our model plans describe the correct amount of insulation required to protect the fuselage from the heat of this powerful engine. These jet propelled scale models are the most advanced type of model aircraft and should not be attempted by the novice. Complete weight should be under 4½ pounds.

At this time, both fuselage shells must be lined with an insulating material. Asbestos-magnesia powder can be wet with water and mixed to the consistency of a thick paste and a thick coating applied to the interior to a thickness of about ¼". It is not necessary to coat the fuselage forward of the fuel tank. This will dry, resembling plaster. Let it set overnight.

It will be noted that an insulating cone is used to keep the heat away from the shell. During flight, air rushes into the air scoops and front-wheel well opening. A small fraction of this air is consumed by the power plant, but the greater portion courses through the two air spaces: one between the engine and metal cone and the other between the cone and the shell insulation. This air carries most of the engine heat out through the tail openings.

Cut out and bend the 1/16" aluminum insulating cone at this time. It is advisable first to cut this item from stiff paper in order to ascertain its proper shape. The rear portion of the cone is slit eight times; four tabs are later bent inward and four tabs bent outward. These inside tabs will hold the jet engine tailpipe steady; the outer tabs are screwed to the fuselage rear. It will be seen that the cone is suspended in the fuselage by means of four bolts.

At this time, the stainless-steel straps and clips can be cut to shape with a hack saw and bent to shape. Bolt the straps to the clips and screw the clips to the hardwood foundation. Before the power plant is slid into the strap, the insulating cone must be installed. Drill four ⅛″ holes in the sides, top, and bottom of the metal cone. Fit steel bolts through the side holes and the bottom hole, piercing the fuselage. Slip a fibre washer, followed by a nut, onto the bolt from the outside of the fuselage and tighten these carefully, alternating from the sides and bottom until the cone is somewhat suspended. The top bolt, which is installed later, will assist this suspension operation. Slide the "Dyna-Jet" power plant into the engine-mounting stainless steel strap and fit a bolt through the top. This can be tightened by working through the ¾" diameter hole in the metal insulating cone. Once this is tightened, the rear tabs on the aluminum sheet can be bent. Four tabs are bent outward and are screwed to the 3/16" plywood. The remaining four tabs are bent inward and thus hold the "Dyna-Jet" tailpipe steady.

These jet engines consume more fuel than the reciprocating type of power plant and, therefore, require a larger tank. An ordinary tin can can be converted into an excellent fuel tank. Cut away part of the side and top, solder these closed and add the filling, vent, and feed lines. These are short lengths of ⅛" I.D. brass or copper tubing.  Be certain to fit the drain line into the fuselage just aft of the fuel tank in order to remove any gasoline that may be spilled in the fuselage. This gasoline would create a serious fire hazard if not removed. Note the angle of the forward portion of the fuel tank. This is made in this manner in order to deflect the air entering the wheel well to the upper portion of the fuselage, where most of the heat will accumulate.

Curtiss Automotive Photo

This "Dyna-Jet" powered "Bell X-l" was built without a landing gear. Take off was from this wire "dolly" which remains on the ground when the model becomes airborne. This replica is of the same plane described in Chapter One as a "Whip Control Model". The advanced modeller could develop plans of a jet propelled "Bell X-l" by using the plans in Chapter One and by following the jet model requirements described in this chapter. Note that the cockpit is left windowless to enable air to enter the fuselage.

Before the fuselage top is installed, it would be wise to afix some lead weight in the nose of the lower half just forward of the nose landing gear.   Add eight ounces as the initial ballast. When the craft is completed, additional weight can be added through the nose wheel opening.

Carefully cut the hatch in the upper fuselage half. A very sharp single-edge razor blade is recommended for this operation. When this is done, the fuselage top can be glued rigidly to the lower half. A good grade of casein glue is ideal for this job. Do not use cement because of its inflammable character.

After the two fuselage halves are dry, the top bolt can be fitted to suspend the 1/16" aluminum-sheet insulating cone. Once this is firmly suspended and does not touch either the engine or fuselage, the nuts are recessed into the fuselage. Do not forget the fibre washers. The nuts are covered with "Plastic Balsa."

Use a small commercial hinge to attach the hatch to the body. There are numerous types of fastenings to hold the hatch closed available at hardware stores. A spring-type closing is recommended.

Sand the model smooth and apply as many coats of sanding sealer as you desire. The model is colored aluminum with black trim and standard insignia. The cockpit cover is cut from a standard canopy furnished in many airplane kits being marketed today. Many "Berkely" kits contain canopies that will fit our model. These are also sold separately. No fuel proofer is needed on any jet-propelled models.

For ease of construction, the control rod is located on the outside of the model. This item is now connected to the control horn.

The important item to stress in flying these craft is the fact that haste and teamwork are required during engine starting. These engines heat up unbelievably when not in motion, and must therefore be flown within a few seconds after the engine is started. Upon landing, the hatch should be opened immediately to allow the hot air to escape. Flight lines should not be smaller than .016" in diameter and should be braided stainless steel. This craft can be flown on from 40- to 80-foot lines. Manufacturer's engine-operating instructions are included with each engine. Be sure to follow them carefully.

Lockheed  Aircraft   Photo

In constructing our model of the "F-80" it is most important to carve and hollow the air intake scoops on each side of the fuselage in order to force as much air as possible through the hollow fuselage in order to dissipate the heat generated by the jet engine. Even the nose wheel door opening should be cut open and a scoop fitted as the plans illustrate. The fuselage scoops are clearly shown in this photo of the "real thing".

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