Designing a balsa wood glider is similar to designing a full-sized glider and applies many of the same principles of flight. Specifically, the main design features the wing shape and size, the wing placement and the overall tail size. Balsa wood or heavy oak paper can be used. The balsa wood is heavier, so steps must be taken to conserve the model's weight. Balsa wood holds its form better and is easier to build parts with than paper.

- Skill level:
- Easy

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### Things you need

- 3 mm (1/8 inch) balsa wood sheeting
- 6 mm x 1.3 mm (1/4 inch x 1/2 inch) balsa wood strip about 60 cm (2 feet) in length
- Wood glue (Testor's or equivalent)
- Sandpaper (assorted)
- Razor blade or knife
- Pen
- Ruler

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## Instructions

- 1
Determine the wing shape and size. Use a simple rectangular shape for the wing configuration to reduce calculations. The shape also is important in determining the other dimensions to be designed for the glider.

- 2
Design the size of the horizontal stabiliser. Use the formula SH (the surface area of the horizontal stabiliser in cm.sq.) = 1.2 S (the main wing surface area in cm.sq.) times the chord length of the main wing in cm. divided by the DCG (the distance from the centre of gravity to the horizontal stabiliser). The horizontal stabiliser is equal to the wing area times the chord and then divided by the distance from the centre of gravity times 1.2. Plug your ideal numbers into this formula. The tail will probably be too big. The way to fix this is to reduce the wing chord and make the wings longer end to end to provide enough surface area. Try several sizes and experiment on glider dimensions and how it will appear when completed.

- 3
Design the vertical stabiliser. Use the equation SV = S times SP divided by DCG multiplied by .05, where S and DCG are the same as used in the above formula. SP = the wing span and SV = surface area of vertical stabilisers. You have calculated an area in cubic centimetres. Now convert that area to a nominal length times width. These values for the vertical stabiliser should be acceptable to the design.

- 4
Construct the glider using the values you have designed from the above formulas. Use a pen to draw the wings and stabilisers on balsa sheeting. Cut parts out from balsa sheeting.

- 5
Curve the wings slightly to take advantage of Bernoulli's principle of a lift over a curved airfoil. Brace the wings in a curved position overnight. Place curved wings on the top of the body, locating centre of gravity so it is about a quarter of the total wing chord in from the leading edge. Add a dihedral of 5-15 degrees (wing ends are tipped up from body). Also, the wing angle of attack should be set at 2 degrees (pitched slightly forward). Glue wings to body in this position. Set aside to dry.

- 6
Glue the vertical and horizontal stabilisers as calculated in your design to the body. Mount these pieces flat without any up or down or right or left. Glue and set aside to dry.

- 7
Cut body size to fit model scale after addition of wings and stabilisers.

#### Tips and warnings

- Glue with extra fast drying wood glue.
- Use glue in small amounts
- Sandpaper wing and body to reduce weight.
- Avoid flying the model near overhead power lines.
- Additional adjustments may have to be made to fly the model