For years, scholars and scientists have theorised about the design and construction methods of Noah's ark. The Bible gives the Ark's dimensions as 300 cubits long, by 50 cubits wide, by 30 cubits high. It was built to carry two of each species of animal. To make a scale model of Noah's Ark, you must rely somewhat on the imagination, however, scholars have determined the ark likely resembled a rectangular box. A variation of this design with a rounded bow and stern has become accepted by Christian culture as the archetype for Noah's Ark.
Determine the scale you want to use. This is the size of the finished ship. Online resources can help you do the scale conversions. Converting the cubit measurements to feet would result in a length of 450 feet, a width of 75 feet and a height of 45 feet.
Lay out your plans based on the scale you have determined. The plans should include a rib structure -- like the frame of a house -- on which you will paste the wood planks and a twig roof.
Construct the frame using the balsa wood strips. Lay out and glue together a rectangular base and an identical rectangular structure for the top of the hull. Cut out ribs to the height specified in your plans and glue them to the base. Glue the top hull structure onto the tops of the ribs. You should have a rectangular frame.
Cut strips from the balsa wood sheets to use as planking. Vary their sizes so they don't all fit together uniformly when glued to the frame. To determine the length of a plank, measure the distance between the two ribs to which the plank will be attached. Glue each plank to the ribs.
Glue the twigs side by side across the width of the vessel on top of the hull from the bow to the stern. Allow each twig to overhang slightly.
Cut out a rectangular piece of balsa wood sheet to affix to the bottom of the Ark and glue it in place. Sand the entire ship with 300-grit sandpaper. If there are any areas that protrude, you can shape them with the sandpaper.
Stain the balsa wood areas of the ship. Allow to dry, then apply a coat of matt varnish to the entire ship.
You can add detail to your ark with enamel paint.