Light Outdoor Tractor (oz13644)

About this Plan

Light Outdoor Tractor. Rubber stick model.

Quote: "Building a Light Outdoor Tractor. A High Altitude Plane With Free Wheeling Propeller That You Can Construct Easily from These Plans. By Gilbert MacLean.

Probably many young model builders remember and have possibly built small indoor stick models that have been on the market for a number of years. The main object of these airplanes was to provide a plane which would fly, yet which could be easily and simply constructed.

In presenting this model for the model builder, great care has been taken to embody these same simple operations without intricate and complicated work and without changing the design and form of the plane; so that it will give a performance commensurate with the best contest models. This provides a chance for the mere novice to break into the contest field. One might say that it is the first step from the amateur model to the expert's contest model.

The ship is not very large, having only a span of twenty-two inches and the wing area is sixty-eight square inches. This places it in the 'B' class. It cannot be used in all contests. However, in many of them, there are 'Free-For-All' events, in which case, this ship may be used with good effect. If the weight rule is included in the particular event in which you wish to enter, the weight of the model may be increased to one and one-third ounces, as required, by adding weight to the wheels. When it is necessary to weight the model this is the proper place to put the weight, unless you desire more rubber, a larger propeller and a larger motor stick. This, however, is not always possible or advisable. Adding weight to the wheels will give your model unusual stability and through this means increase its efficiency in flight.

The little ship has been primarily designed as a fast climbing altitude plane, basing its design around the theory that duration is more often obtained by models whose propeller is of medium size, yet which has sufficient power to have it climb rapidly to a great height. Under these conditions it is more likely that the model will find a rising or thermal air current upon which it can fly for longer duration. Then again, while gliding, the propeller is smaller than the usual duration ship. This adds to the efficiency of the glide as the propeller then gives little resistance. This is true, even though the propeller may be fitted with a free wheeling device, as in the case of this model.

The motor stick has been made unusually long in order to get more turns upon the rubber which will compensate for the fact that the propeller's diameter is not large but turns faster than ones used usually on duration ships. The performance of this model is unlimited. The duration of the propeller is about seventy seconds. However, at the end of the seventy second period it should have attained great altitude. Even in still air the glide added to the power-driven time should bring the duration well up into the two or three minute class. The model has made some remarkable flights, has proved unusually stable and should be a joy to any model builder who completes its construction. Without question you will want to build this little machine, so we will now tell you how to proceed.

Motor Stick: Start your construction by making the motor stick. Cut it to shape and sand lightly. Make it from a piece of medium hard balsa, 22 in long, 3/8 high and 3/16 wide. Three and a half inches from the end which you select as the front end, place a mark. Bevel the top surface of the stick down toward the nose so that the height of the stick at the nose is 3/16 in. Place a mark on the top of the stick eleven inches from the rear end of the stick and another on the side three inches from the rear. At this latter point measure up 3/16 from the bottom of the stick. From this point draw a line forward and upward along the stick to the point on the upper side eleven inches from the rear. Now, on the rear end of the stick, mark a point 5/32" up from the bottom of the stick. Draw a line from this point forward, down slightly to the point which is three inches from the rear end of the stick.

Now, cut away the top of the stick to these lines. See side view drawing. When this is finished, bevel up the lower side of the stick from the point three inches from the rear, to the rear, as shown in the drawing. The stick at the rear should be 1/16 deep. Throughout its length the stick is 3/32 wide. Do not sandpaper the side of the top stick at the rear. The elevator is to be cemented to this surface.

Wing: Next proceed to make the wing. The first operation is to cut out the ribs, using the patterns on the drawing. The notches in the ribs which are cross-lined, indicate where the spars are to pass through.

Next make your spars. The front and rear spars each are 10-5/8 long. There are two sets of them. As the wing is tapered, the spars do not run straight from tip to tip. Therefore, the wing is made in two sections, before cementing the spars together. In cutting the spars, it is wise to cut each one from the same strip of wood, taking pieces 20-5/8 long and cutting them in half.

Both the front and rear spars are 1/4 in wide and 3/32 deep at the center of the wing. On the drawing the front spar is shown as 1/32 deep. This is an error. They should be bevelled slightly from the center to the tip, so that the thickness is 1/16 at the wing tip. The width at the wing tip is 3/16..."

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