How to Make a Cardboard Box Submarine

Lay the large wardrobe style cardboard box on its side. Mark the four long sides of the box A, B, C and D. Mark the short ends E and F. Fold the box flat.

Lay a paper plate in the approximate center of side A and trace it with a marker. Trace a second and third circle in the same manner on either side of the first, keeping the spacing even. Repeat this on side C.

Place a cutting mat inside the box so you don't cut through more than one layer of cardboard at a time. Use a box cutter to cut out the circles to create portholes. Set aside the circles you cut out; they will be used later.

Center the cardboard box on top of the flattened side B of the wardrobe box. Use a marker to trace the outline of the cardboard box onto the wardrobe box and then cut it out with the box cutter, using the cutting mat underneath.The cardboard box is going to be the canopy compartment on top of the sub.

Draw eight right triangles on the circles that were cut out for the portholes. These will be braces to keep the wardrobe box supported.

Unflatten the wardrobe box and open it up. Place four brace triangles in each end of the box, one in each corner. Attach the triangles with tape to make the sub sturdy. Seal the ends of the box with tape.

Attach silver metallic wrapping paper or aluminum foil to the large box with tape. Cut out holes for the portholes and canopy opening, starting the cut with the box cutter and finishing it up with scissors.

Use a marker to draw rims and rivets around the outside of the portholes. Rivets are the bolts that are used to hold the window on and the rims would the metal circle that goes around the outside of the window.

Create portholes on one side of the smaller cardboard box by tracing the paper plate and then cutting out with the box cutter.

Cover the smaller cardboard box with the metallic wrapping paper the same way you did the wardrobe box. Use the same paper or a different color.

Make covers for the portholes by cutting out squares of blue cellophane. Use tape to adhere the cellophane windows to the inside of both boxes. This will create an underwater look when you are in the sub.

Make the propeller by tracing a square on a piece of gold poster board. Use the length of your cutting mat as a guide. Cut the square out with scissors. Draw diagonal lines from corner to corner on the poster board. Cut along the lines, but do not cut them all the way out. Leave an inch on each line so that you have four attached triangles. This will be your propeller.

Poke a hole in each triangle using a wooden skewer. The holes should be in the top left corner of each.

Use masking tape to attach two skewers together, end to end. Cover in silver metallic tape, leaving an inch uncovered at either end. Insert the skewers through the center of your propeller. Insert the end of the skewer through the holes you made in the corners of the triangles. Tape it in place. It should look like a pinwheel. Use scissors to round the edges of the triangles to make them look more like propeller blades.

Use duct tape to attach a piece of curved PVC piping to the top center of the small cardboard box to use as a periscope. If desired, spray it with silver spray paint first.

Insert the end of the propeller skewer through side E of the wardrobe box.

Help your child into the box through the large canopy hole you cut in the top. Place the small cardboard box over the top to finish the sub.