Paper Boat
 
 

What is the Paper Boat?
The paper boat is a folded boat able to swim - for a while.
Obviously it is well known all over the world. 

Folding a Paper Boat  top
1
Take a sheet of paper of the size A4 (8 1/2" x 11"). Paper used for ink jet printers will do. 

Fold the upper half down on the red line.

2
Find the centre line by folding the left side on the right side and by unfolding.
3
Fold downward both upper triangles on the red line.
4
It must look like this. 
5
At the bottom fold the top strip upward on the red line.
6
Fold the two small triangles on the left and on the right backwards to make them disappear.
7
It must look like this.
8
Turn the paper over and fold the other lower strip
upwards. You have formed the well known hat.
9
Turn the hat 90 degrees and open it. The thumbs must be inside. Lay the upper and the lower parts on each other.
10
It must look like this. 
11
Fold the lower front triangle upwards on the red line.
12
It must look like this. .
.
13
Turn the paper over and fold up the other lower triangle. You get a hat without a brim.
14
Open the hat again and put the upper part on the lower one.
15
Pull the upper corners of the triangles in direction of the arrows...
16
Pull the upper corners of the triangles in direction of the arrows...
... as much as possible. Form the boat. 

The paper boat is finished.
 

If using 8.5" x 11" ink jet paper the sail will be
visible above the sides of the boat.
 

17
Stretch the boat both to the right and left, and then separate it slightly from underneath so it can float.


The Boat With Three Sails top
Perhaps it is unknown, that you can give the boat three "sails" in the middle. 
Don't make step 15. Fold the lower front triangle upwards on the red line. Turn the paper over and repeat this folding. 
It must look like this. 
Turn the hat 90 degrees and open it. Lay the upper and the lower parts on each other.
Pull the upper corners of the triangles in direction of the arrows. Form the boat. 
If the paper is not too thick, you even can repeat these steps and look for more sails ;-).


The Boat with a Big Sail top
Follow steps 1 to 10. 
Fold the lower front triangle upwards on the red line and unfold. So you find the centre of the square.
Fold the lower front triangle upwards on the red line. The tip should touch the centre of the square. 
It must look like this.

Turn the paper over and fold the lower front triangle upwards, too.

Make the steps 14, 15 und 16.

If the lower triangles are a little bit larger, the sail will be smaller.

The Best Paper Size  top
...... If you use A4 paper and if you colour the outer walls of the boat red and the inside walls pink and unfold the sheet, you'll get the results on the left. The strips belonging to the inside walls are a bit too narrow. It would be ideal, if the pink strips were the same height as the red ones. This would work with the size 6:4=1.5. The sheet A4 has the size 1:1.4 (=1: [square root of 2]).

The net also shows all boats are equivalent. 

Only the width of the paper and not the height influences the size of the boat. 


Some Mathematics  top
From the mathematical point of view the start for the boat is a shape of two isosceles, right-angled triangles connected at the sides at the right angle. You get the boat, if you reflect the lower parts of the two triangles on the middle (red) line.

 
... The boat has three parts, the front side, the reverse side and the sail. The unfolded sheet (on the far left) shows these parts. The boat has only a vertical symmetry axis.


Thats it your boat is complete enjoy