Martian Invader (Mar, 1956)
Is it a bird? Is it a plane? No, it’s MPs interplanetary space traveler.
By Walter A. Musciano
HERE is a model that can truly be described as being “out of this world.” The Mechanix Illustrated Martian Invader, a flying saucer, is a most unusual control line model airplane patterned along the lines of those luminous disks that thousands of people have seen during the past several years.
The twin bubble canopies housing the Martian pilot and his robot and the rakish fins add to the futuristic appearance of our saucer.
The six-ounce craft can be powered with any .039 to .074 cubic-inch displacement glow plug or diesel engine. It does not matter whether the engine has an attached fuel tank or not, this plane will accommodate it. The fact that the entire body contributes to the lift, coupled with the symmetrical airfoil, creates a craft that is ideal for stunting purposes. The two balance points for sport or stunt flying will be described later.
Construction has been simplified to the point where only two sizes of balsa wood sheet and one size plywood are required to complete this model. Although easy to build, it will simplify matters if the full size plans are used for construction.
Start by tracing parts 1 to 13 onto hard 1/8-in. sheet balsa. Follow this by tracing the bulkhead, landing gear support and bellcrank support onto 1/8-in. plywood. Cut the sheet balsa pieces to shape with a single edge razor blade or jig saw. The plywood can be cut with a jig or coping saw. Sand all pieces smooth with 3/0 sandpaper. Cement the plywood bulkhead and bellcrank support to the pieces No. 4. Slip the forward spar, piece No. 1, through pieces No. 4 and cement well; follow this with spars No. 2 and 3. When the cement has dried slip ribs Nos. 5,6 and 7 onto the spars to form an “egg crate” structure. Trace and cut pieces Nos. 8, 9, 10, 11 and 12 to shape. Cement these very securely to the ribs, spars and No. 4.
Attach the elevator, No. 13, to No. 12 by using cloth hinges; these are first cemented to the top and bottom of the elevator. While drying install the control horn. Slip the horn onto the elevator and cement this firmly. Bend the control rod to shape with pliers and ship the offset end through the control horn hole. Pass the control rod through the holes in the spars. Now, cement the remainder of the cloth hinges to piece No. 12, alternating as shown, top and bottom. Smear another coat of cement over the cloth hinge attachment.
Before the bellcrank is installed the wire lead-out lines must be attached. Twist the ends as shown to insure a firm attachment. Slip the lead-out wires through the holes in the ribs and slip the bent-up portion of the control rod through the bellcrank hole, and bolt the bellcrank in place. Be certain to include washers between the bellcrank and the bellcrank support. The control system should move freely. Solder-seal the nut holding the bellcrank in place and cement the tailskid support between pieces No. 4 as shown.
Bend the landing gear to shape with pliers following the pattern on the plan. Cement this between the plywood bulkhead and the landing gear support. Use plenty of the adhesive and apply several coats.
The upper surface of the disk forward of spar No. 1 is covered with 1/32-in. sheet balsa. Apply cement to the ribs, spar and piece No. 8 and part of No. 9. Press the 1/32-in. sheet balsa in place and hold to the structure with straight pins until dry.
If a commercial stunt tank is to be used install it now; this must be very securely attached to the plane structure. Brace the tank with scrap balsa and plenty of cement. Any commercial tank of 1/2-ounce capacity can be used such as Perfect, Maeco, Froom, Kap Pak or Acme. Make certain that the filling and overflow lines extend to the outside of the model; add plastic tube extensions if required. It is also important that the plastic tube feed line be long enough to reach the engine without kinks. Make a hole in the bulkhead for this feed line.
The space between pieces No. 4 is now covered with 1/32-in. sheet balsa. Cut the covering to shape and apply cement atop pieces No. 4 and the bulkhead and the tailskid support. Hold the sheet balsa in place with straight pins until the cement dries.
Remove all straight pins and sandpaper the entire structure very thoroughly. When smooth, and all rib and spar junctions are level, all joints should be â€¢re-cemented. Now, cover the entire model with Silkspan or Sky Sail, obtainable at all hobby counters. The disk is covered in four piecesâ€”two top and two bottom. The grain of the covering should run from nose to tail. Apply cement to rib piece No. 5 and Nos. 8, 9, 10, 11 and 12 on one side only. Now, quickly lay the paper covering in place and stretch it as smooth as possible while pressing it against the cement.
When the plane is completely covered carefully trim away the excess paper with a sharp razor and sand gently. Wet a wad of cotton and very gently pass it over the covering to moisten it and make it shrink; set aside to dry thoroughly.
While drying, the fins can be made. Trace and cut these from hard sheet balsa. Note the grain direction. Sand the fins to a smooth and streamlined shape and cement in place when the covering is dry. Also, bend and cement the tailskid in place.
If all the wrinkles have not disappeared from the covering wet it again and let dry. Brush three consecutive coats of clear model airplane dope onto the entire model. Wait until the one coat has dried before applying the next. Sand this very, very lightly at this time. Brush on two more coats and the model is ready to be painted.
The color of the prototype model is bright yellow with red and blue trim. First paint the entire model with yellow model airplane dope, using a 3/8-in. flat camel hair brush. Three coats should produce a good finish. Use paper masking tape for a neat trimming job. Apply the tape along the color lines to protect areas that are not to be painted. Brush three coats of red dope onto the sides of the disk; the round ports are also red. The area covered by the plastic bubbles and the lighting bolt is blue.
The bubble canopies are standard items and can be purchased at most hobby shops. These need not be the specific canopies mentioned on the plan. Our transparent enclosures can be had for about forty cents each from Berkeley Models, West Hempstead, N. Y. These were cut down with scissors to the size shown. The Martian pilot and his robot can be carved from balsa wood or can be cut from plastic toys and modified with wire springs, etc.
Screw the engine onto the bulkhead and attach the propeller. Most 5-1/2 or 6-in. diameter propellers can be used of about 3 or 4-in. pitch. In order to prevent broken propellers we recommend the new Whizzer nylon propellers which are virtually unbreakable. The 1/32-in. sheet covering under the engine is optional but can be added at this time. The grain should run crosswise to facilitate bending. Paint the inside several times before this sheet is cemented in place. Now, paint the exterior and the model is ready for flying.
Fuel-proof dope should be used on the model to protect it from fuel stains. If fuel-proof dope has not been used, brush or spray two coats of Tuff transparent fuel proofer onto the entire model in order to prevent the fuel from softening the paint.
The model should balance correctly before any flying is attempted. The novice should balance his craft at the sport flying balance line or even slightly forward of this line. For average stunt flying, balance the model as shown on the plan. The veteran model flyer who desires a super stunting model eligible for competition flying needs to merely enlarge the elevator as shown on the plan. As a general rule the further forward the model balances the less sensitive it is and therefore easier to fly. As the balance point is moved aft the model becomes more sensitive, which is excellent for stunting, but be sure you can handle it. Remedy any unbalanced condition with lead weight, firmly fastened in the nose or tail.
The Martian Invader can be flown on heavy carpet thread flight lines from twenty to forty feet long. Start with the shorter lines and graduate to the longer lines as experience is gained. It is advisable to fly from a relatively smooth surface â€”a paved area is ideal. Select your flying area and connect the flight lines to the lead out wires on the model. Place the control handle in the center of the circle and then start the engine according to the manufacturer’s instructions. Have your helper restrain the model, after the engine has started, while you walk to the control handle. Check the controls quickly, survey the flight area to be certain it is clear of spectators, then signal your helper to release (not push) the model. It should be released facing downwind. Let the craft take off by itself with the controls neutral.
When the engine stops, keep turning with the model and lead it into a smooth landing. If built with care and flown with common sense the Martian Invader is certain to provide countless hours of flying enjoyment with a most unusual model.