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A High Performance  Flyabout

By E. LIDGARD

Here Is an All Balsa "Experimental" Model That Gives
Contest Performance Though It Is Easy to Build

 
Here it is, up and going places.

EVERY fellow who follows this fascinating hobby of ours has some pet ship. It may not be streamlined, it may not be beautiful to look upon, but it flies! It may be battered and worn, but from past experience it has proven that irregardless of weather or time, it can he flown at a minute's notice. The plane presented here is my favorite. The original lasted almost two years daring which time it served as an experimenter for various ideas. Its last flight was made while waiting for a part to dry on a Wakefield model. It disappeared into the blue, after six minutes, over the Chicago Municipal Airport. A few days later, Foo II" was built. It also is a good consistent flier.

Whether you are a beginner or a consistent contest placer, you will enjoy building and flying this simple ship. Incidentally, it won't take mach time to build. With any past experience at all, eight or nine hours should be sufficient. As for cost, 75c will cover everything.

Most builders who do a great deal of flying like larger ships than this one. However, this ship has performance which is directly proportional to that of a larger ship of the same wing loading. A minute and one half to three minute flights, with 700 hand winds, are not uncommon. And with a slight amount of luck on a good day, it stands even chances of being lost.

If your interest has been aroused, let's start construction. In buying your materials, get all quarter-grained balsa, commonly called "C" stock. This cut of balsa is stiffer and does not warp, and makes far more sturdy construction and long lasting adjustments. Try also to get a hand balsa machine cut prop plank. In case of doubt in any phase of construction, make it on the sturdy side, because in order to meet the 3 oz. per 100 square inch weight rule, it should weigh 2.7 oz. Although the ship is too small for contest use, being under 100 square inches, it is a good idea to make it  weight rule so as to keep  in trim for flying ships  which are required to  meet it.

We'll start construction with the fuselage. The entire ship is of all-balsa construction. This type of construction is very strong, yet fairly light. It is very durable, easy to build and repair. To lay out the fuselage sides, templates of cardboard are first made. The top and bottom may be scaled right up from the 3/8" scale graphed view. The bottom is made 1/4" longer than the top, to allow for the curve. To lay off the sides do as follows. On a large piece of cardboard draw the base line. This is eighteen inches long. Allow a clearance of three inches on bottom and one inch on top. Now at the front extremity measure up 9/16" vertically from the line, and at the tail end of the line, construct a similar line 7/16 long. Connect the two and that takes care of the top of the holy. The bottom must be plotted to get the correct curve. From the nose end, lay off eight dots on the base line, 5/8" apart, making a total of five inches. From the five inch point lay off another dot 1-1/4" beyond. From these nine dots draw lines at least two inches long down from the dots, and at right angles to the base line. It is now easy to plot the negative ordinates just by following the dimensions on the plans. Connect the ordinate dots by a curved line, and connect the last dot with the end of the base line at the tail. Now the fuselage side is all plotted, and it should be cut out with a razor and then traced onto the 1/16" sheet balsa for the sides. Corners are reinforced with 1/16" square strips. They give more gluing surface for the joints and allow for sanding the corners round. A coat of banana oil on the inside surfaces prevents the rubber lubricant from rotting the wood. Use plenty of glue for all joints, especially the rear motor hook. Do not forget the rubber tubing around the rear rubber hook because it is difficult to insert after the fuselage is all assembled. Slits in the sides, top and bottom are cut to accommodate the elevator and rudder. Coat the nose plug inside and out with cement, to prevent wear due to winding and handling.

The landing gear is made of No. 18 music wire (as are all wire fittings). Use glue generously and attach the whole gear to its proper place, which is well forward with the wheels just clear of the propeller. A 1/64" sheet fairing adds strength and looks to the ship. A pair of 1-1/4" hardwood wheels are held on by washers soldered to the wire struts.

The propeller is cut from a ten-inch machine cut blank, or from a block 5/8" x 1" x 10" hard balsa. It is imperative that the shaft be perfectly straight and true, because a wobbly propeller absorbs a great deal of the available power. A "Jasco" free wheeler and brass B.B. washer are used. Small brass bushings set in thin sheet brass form the bearing surface for the propeller shaft. The same type of bushings are used on the nose plug, which is built up of scraps of sheet and a cylindrical block 5/8" x 3/4".

The tail works are very simple, being made of two inch sheets glued edge to edge. The outlines are cut out and the surfaces are sanded down smooth to 1/32" at all edges. To prevent the tips from fraying, they are given a coat of glue, carefully applied to prevent warping.

To some this type of wing construction may seem too heavy, but there is logic behind its choice. (1) It does not raise the C.G. any higher than the average ship, but because heavy wheels and fuselage of sturdy construction counterbalance it. (2) A wing of very strong construction is ideal for experimenting and all-weather flying. (3) Because of its small area, every possible method should be used to obtain maximum efficiency for a high L/D. This type of wing yields a smooth, true airfoil devoid of spar and trailing edge bumps so common to a built‑up wing.

It is very easy to construct. Four 1/32" x 2" x 24" sheets are glued together to form upper and lower cambers. They are sanded very thin and smooth. The ribs are cut about 1/32" smaller all around to make up for the thickness of the covering. Although no spar is needed, one may be used to simplify construction. The lower camber is glued to the ribs first and then the upper camber is glued on and blocked down. In order to obtain a thin trailing edge, both sheets are sanded to a very thin taper and glued slightly overlapping, the under camber slightly overlapping the upper camber. The leading edge is glued on and sanded to the proper shape. To prevent wear and fraying, the leading edge and tips are given a coat of glue. This coat, however, should not go further than one‑half inch from the edge; otherwise the glue will warp the thin sheet covering. The No. 18 music wire mounts are bent and inserted into the wings and glued on. To prevent their becoming loose thin aluminum guards are used. The wing mount is the only thing upon which glue should be used sparingly. The reason is that a heavy coat of glue put on in one small place on a thin sheet tends to curl up at the extremities of the glue skin. This eventually increases and peels off. It may also warp the sheet. It has been found on the original ship that a little glue applied right is very strong. The ailerons are cut out as a final operation and are held in place by one inch pieces of aluminum wire, glued to the ribs.

The fact that this ship is small does not affect adjustment methods as its larger predecessor. It has a short, fast, powerful climb and flat glide. With half the maximum turns, hand wound, it will turn in a minute and a half flight consistently. Winder wound to 1300 turns it stands an even chance of being lost every flight. When properly adjusted, it should fly as follows: An extremely steep, almost vertical, climb to 100 feet where it gradually rolls out into a steep spiral climb to the right. There should be no dip when the power gives out. The glide is very flat, with a tight right circle. It is suggested that the adjustments of the original model be used until its flight characteristics are mastered. It must be kept in mind that this ship is very high powered and thought must be given to every adjustment.

Wing:

Adjustments - Set positive two degrees to the rubber base line, right aileron 1/8" down, left aileron 1/8" up.

Elevator:

Set one degree negative to rubber base line. Not to be warped.

Rudders:

Warped approximately 1/16" to the right. This will vary with individual models in order to get the proper turn.

Thrust Line:

1/16" down thrust and 1/32" right thrust..

A 24-inch motor of 14 strands of 1/8" M.R.L. brown rubber is used for power. To those unaccustomed to high power it is suggested that ten strands be used at first and gradually work up to fourteen strands. A good grade of rubber lubricant should be used for best results.

All comments, criticisms, or corrections on this design, would be appreciated. 

Bill of Materials

Cost ‑- 75c to $1.00, depending upon where the material is bought.

Scanned From August 1938
Model Airplane News

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