Foldable Glider

For a school project we had to design a glider that glides as far as possible. As an bonus I chose to design an aircraft that can easely be transported. The wings of the plane are folded backwards and the tail fins can be folded down. The look of the aircraft is based on a dragonfly.

to build this glider you need the following materials:

-3x1x100 cm balsa square dowels

-10x1x100 cm balsa board x2

-a large piece of insulating foam that can be cut with a hot wire ca 60 x 8 x 50 cm

-a sheet of 5mm plywood approximately 30 x 30 cm

-a piece of 10mm plywood approximately 5 x 30 cm

-some hinges x 4

- screws, bolts and nuts

-6 mm dowel

-6 mm arrow shaft ( ore an aluminum shaft)

-piece of rubber

-2 x 10 x 120 mm piece of aluminum x2

To build the nose you need to first draw the shape of the nose on a sheet of cardboard. the shape of the nose must fit in a 45 cm x 16 cm rectangle. the nose exist out of 3 layers of balsa wood.

The inner layer consist of 2 pieces of 10x1x100 cm balsa wood edge jointed together. the two pieces must be orientated so the grain of the wood follows the length of the shape. begin the inner layer with cutting of a piece of balsa where most of your cardboard template fits in. Then cut out a smaller piece that can be glued on the larger piece so the template fits on your boards. Now cut roughly your templates shape out of the balsa board.

For the two outer layers of the nose. start at the front of the nose and cut and glue pieces of 10 X 1 cm balsa. note that the direction of the grain is perpendicular to the grain of the inner layer. now keep gluing pieces of balsa next to each other until you reach the back of the shape . Do this on both sides.

now sand the shape until it has a very nice round shape. keep the front of the nose thicker than the back to keep the weight at the front. from 22 cm of the front of the nose keep the top as flat as possible.

To build the body , first start with cutting a template of a wing shape out of the 5mm plywood. the wing shape must be approximately 21 cm long and 3 cm high. this template will become very handy later in the build.

to build the wing attachment point, trace your template on the piece of 10 mm plywood and draw two protrusions at the bottom of the drawing ( see picture) . approximately 3 cm long. the spacing between must be large enough so a hand can fit trough it.

now trace your templates protrusions onto the top of the nose. with the front of the part approximately 22 cm from the nose of the nose. after marking the space you can use a chisel and a hammer ( or a dremel) to remove material up to 1 cm deep. keep testing the fit to ensure the hole isn't to big. after a satisfied fit, glue the piece in the hole. (note the underside of the wing shape must be parallel to the top of the nose).

make your 3 cm x 1 balsa lath 80 cm long. and use a box cutter to narrow the the lath towards the end. after this you can glue the lath onto the nose and wing attachment point (see picture).

cut out of the 5 mm plywood 2 pieces of 3 cm x 10 cm. these two pieces need to be glued on the place where the wing attachment point and the lath meet. with one of the edges flush with the hole in the wing attachment point.

to cut out the wing we use the hot wire cutting method as demonstrated in this video.

we use the wing template as a cutting template. note that after cutting the first wing the template must be reversed to cut the other wing.each wing has to have a length of 60 cm

now cut out 4 more wing shapes out of the 5 mm plywood using our wing template. cutting the shapes is very easy if you stick them together with double sided tape.

now take two of the templates and put the other two aside for now. and drill a 6 mm hole in both of them. Stick them on the end of the two wings using hot glue.

take the arrow shaft and use a file to cut tooth on the end of the shaft. put the other end of the shaft a power drill and drill into the wing trough the hole in the plywood (approximately 30 cm deep). cut 2 pieces of arrow shaft and put them in the drilled hole and secure them with hot glue.

take the two extra wing shaped pieces and put them on either side of the the wing attachment point and clamp them in place. now take your hinge and screw it to the wing piece with 2 screws and the wooden plate with one. this one screw will act as an axle where the hinge can rotate around.

drill two holes with a 6 mm drill trough the three plates at once . the placement isn't that important so use the picture as a guideline. cut two pieces of the 6 mm dowel to a length of 20 mm. and glue them in the center piece.move the hinged pieces away if necessary.

bend the aluminum piece in a U shape with a spacing between the legs of 20 mm so when it is pushed over the three pieces it fits snugly. drill a 6 mm hole at both ends of the legs. press the U bracket back over the three pieces and position it straight. drill now with a 6 mm drill trough the hole in the U bracket in the wing attachment point. now test the clamping of the bracket by putting a M5 bolt tough the hole.

to secure both wing pieces onto the hinged wing shaped pieces we need to cut some pockets into the wing pieces to accumulate for the hinges and the clamp. try to trace as good as possible onto the wing pieces. than use a chisel and box knife and cut the pocket. than hot glue the wings to the hinge pieces.use as little as possible. so when the plane crashes the wings break off.

to make the tail fins , we again use the hot wire method but now we only cut a straight plain. with a box knife we cut a triangle of the rectangle. with some sanding we get a more wing shaped shape.

now cut a piece of 3 x 1 x 6 cm balsa in half. on the underside of both wings cut a pocket were the two pieces fit in and hot glue them in place.

now attach the hinges to the the lath and the tail pieces. the hinges can't be seen from the top.

bend the last piece of aluminum in a 120° corner. than drill a small 3 mm hole in one side of the piece. than hot glue the other leg onto one of the wings. drill a small hole trough the wing and put a M2.5 bold trough it and fasten it whit a nut.

to secure the wings when they are folded up I put two toothpicks in the top of the wing and glue them in place. now cut a piece of rubber that fits around the lath whit holes where the toothpick fit into.