VTO – Build a flying model of the most revolutionary of all aircraft — a plane that takes off vertically. (Nov, 1955)
The only prototype to fly is at the Florida Air Museum, Lakeland, FL. Because the intended engine never arrived the plane never actually took off or landed vertically. Takeoffs and landings were accomplished by attaching wheels for conventional takeoffs and landings although a few transitions were made in flight as well as one instance of bringing it to a hover.
VTO – Build a flying model of the most revolutionary of all aircraft — a plane that takes off vertically.
SOME ten years ago, the United States – Navy initiated a development program for a vertical take-off type of plane. Two aircraft of this new species were built, one by the Convair (Consolidated Vultee) designated XFY-1. The other, built by Lockheed Aircraft is designated XFV-1. A model of the latter is the one we are going to build. These planes are not helicopters or convertiplanes. However, they have attributes of both in their flight patterns. It is said, that if you were to watch a takeoff at maximum power the rising craft would disappear from view in less than a minute . .. that’s power! Not only do they employ the maneuverability of a helicopter and the speed of a jet, they also carry aloft a variety of armament, from heavy machine guns to atomic weapons.
The secret of their phenomenal performance lies in their power plants. Both are powered with Allison Turboprop engines developing approximately 5,500 hp driving contra-rotating three-bladed props through a geared reduction box.
To quote Lockheed test pilot Herman R. (Fish) Salmon, “I’ve flown everything from helicopters to jets, but this is the most powerful plane I’ve ever handled.”
Not only has the Navy revolutionized aviation but, they may force into play new measures in our Continental Air Defense Program. With these new designs any backyard is a military airstrip. The take-offs and landings are executed with such finesse one would think (if aboard) he were riding an elevator.
Our replica is a copy of the Lockheed version right down to the contra-rotating prop, since without it the model would never get airborne. This is the third such model built by the author with many of the bugs worked out. This design is something entirely different in model aviation. Bear in mind the design centers around two requirements. One, is to duplicate the prototype’s vertical take-offs and the second, is to bring the craft down again in one piece to fly again. The model’s design is for free flight all the way.
After careful study of the drawings, proceed by laying out the wing structure. For all spars, 1/16 x 1/8 in. medium grade strips are employed. The ribs are shaped from 1/16 in. stock, a good grade of sanded balsa is preferred. Bear in mind that a minimum amount of weight is most important. Use care and judgment in applying the glue to joints, use it sparingly on the wing and fuselage framework.
Proceed by fastening the lower spars to a suitable work surface. Take note of the dihedral angle. Shape and notch the ribs as shown for the tapered effect and secure in place. Construct the wing, one half at a time, the limiting factor being the dihedral angle. Next fasten the 1/8 in. sq. leading edge and 1/8 x 1/2 in. pre-shaped trailing edge. Complete the structure by adding upper spars as shown. Allowing a sufficient time for drying, remove from the work table and sand smooth all joints on both upper and lower surfaces. Complete the wing panel by adding the 1/32 in. pre-sanded balsa skin covering. If necessary, moisten the curved areas to ease the wrapping of the skin over the wing leading edge. Smooth the applied covering using a fine grit sandpaper.
Our next step is the basic fuselage assembly consisting of a simple crutch and former groupings. Throughout the fuselage construction use top quality presanded 1/16 in. sheet balsa. The crutch of course is first assembled. Mark off on its surface pencil lines, to designate former positions. A wing cut-out is removed from the crutch in the area shown. Cement the wing panel into this opening. When dried, secure in place the shaped formers called for. In cementing these formers, try to keep them square to the surface of the crutch at all times. Allowing time for drying; work may now commence on the tail group.
Select top quality balsa, also 1/16 in. sheet with 3 in. width. The four surfaces are made up of sandwiched layers of 1/16 in. sheet balsa. This procedure gives the needed strength to the tail. When these surfaces are sufficiently dried, reduce them slightly in thickness, sanding to a streamline shape. Take note as to the method of mounting.
At this point the fuselage assembly should have thoroughly dried. Slit former G as shown in four places at a 45° angle. Insert the tail surfaces, cement securely in place and check for proper alignment. Stringers can now be added. Here again using top quality balsa, in. strips. Sand all formers as shown in their various cross sections. Add at this point the in. sheet exhaust pad to the aft fuselage area. Bring to a smooth surface all cemented joints. Prior to setting aside, install a 1×1-1/2 in. dia. cut-out in formers A and B to receive the engine bearing block.
Engine arrangements and components are clearly shown; study them carefully. Brass, tubing and sheet is used in the dimensions given. Solder joints as shown only after the in. tubing telescopes into its mate and rotates freely. Complete the bearing half of the assembly and fasten to the balsa bearing block. The spindle half is next worked on. Assemble as with the bearing, making certain that the spindle rotates in its bearing freely. Solder to the forward spindle disk three mounting screws for the fastening of the Cub engine. When satisfied with the assembly and its operation, insert the engine into the fuselage.
To top off the fuselage, fasten the tail block with the flight hook attached. This assembly is used for a tethered take-off. At this point in our program all surfaces are covered with Silk-Span including the sheet balsa areas. Wet the Silk-Span with water, dry, and apply two coats of clear dope.
A standard 7-1/4 in. bubble canopy is fitted to the fuselage deck, distorted as shown to match the original. The three scoops are shaped using 1/16 in. sheet balsa. Fasten them properly in place, apply tissue to conceal the grain areas. Bear in mind the model has two functions. One is for free flight, the other is to decorate a bookcase or table top.
The second plate carries all the required markings and scale details along with the scale prop and spinner. These added features are used for display purposes only, and are removed for flight. The material used can be most any quality of balsa, finished accordingly.
The wing tip tanks have a touch of simplicity. A sheet of 1/16 x 3 in. is water-soaked and wrapped around a 7/8 in. dia. mandrel. When dry, cement the seam and fasten both the forward and aft blocks. Process these details in a manner similar to the sheeted areas on the main assembly, using clear and colored dopes. While finishing bear in mind that a minimum of weight is our working goal, so spray or brush on the silver pigments, using but one thin coat. The red is brushed on as indicated, first masking off the necessary areas. Having allowed sufficient drying time (about three hours) the balance of trim can be added. The drawings show the proper decal in its proper place. The surface trim lines are either inked or decaled in place, using black Trim-Film.
Having completed this detail work, apply a coat of Comet fuel proofer to all surfaces, also a drop of oil to the spindle for free movement. The final stage of construction is limited to the .035 in. sheet aluminum, contra-rotating prop which mounts on the engine crankcase. You will note that the props rotate in opposite directions permitting vertical flight. Be certain to bend the proper pitch into the aluminum blades permitting the required lift.
Prior to flight, test the engine. Lubricate the moving parts to avoid any danger of binding. Place the fuel lines in such a manner that centrifugal force will not bleed the tank. Our next step is actual flight.
The hook fastened to the tail block is used for a tethered launch. Fasten a string to the hook with the other end fastened to a weight. With the engine running and the model tethered vertically in the air the line is severed at the crucial moment—and away we go. However, a hand launch is most appropriate since it is the quickest method of launching. In closing we would like to mention a simple fact, the above design is a new approach to model aviation. Our main purpose was to get it off the ground vertically and have it return in one piece. This, with care, the model will do.
—Paul J. Palanek •