Robert Youens
Paper Fins
For Water Rockets
Left:  The fin is made from a standard 3 inch by 6 inch note card. First you fold the card in half.

Right:  Now fold the end about 3/16 inch from the base.  This with be the attachment points of the fin. I will refer to it as the base of the fin.
Left:  The folded note card in cut into a trapezoid. This style of fin is called a clipped delta. I typically cut from about 1 inch from the folded edge to the end of the open edge.

Right:  Once the shape is established, you will cut the base of the fin, midway down the length of the fin.
Left:  Now apply contact to the front and back edge of the fin.

Right:  Once cured, you should lay the fin on a flat surface and fold the other half of the fin over to secure the two halves.
Left:  The fin is now spread open to accept the internal support / spar.
Left:  The spar is cut a little shorter than the length of the fin. In this photo you see the measurement being taken from the fin to establish the fold in the note card used for the spar.

Right:  Once the spar note card is folded over you must trim off the extra length.
Left:  I typically draw three lines for the spars. I then draw lines forming the wedge shape of the spar. The base of the spare should be about 3/8 inch wide.

Right:  This a view of a completed spar.
Left:  When the spar is inserted, the points of the spar will go in the corners of the fin.

Right:  When fully inserted the base of the spare will be level with the base of the fin.
Left:  This is a picture of the completed paper fin.

Right:  This is the 1 Liter bottle the the fin will be mounted on.
Left:  To establish the location of the fins, wrap a piece of typing paper around the bottle and mark the full circumference on the paper.

Right:  The full circumference is folded in third to make a jig for locating the fins.
Left:  Once the locating jig is in position you can mark the location of the base of each fin with a permanent marker on the bottle.

Right:  Now position the base of the fin in position and make a mark on the bottle for the top of the fin.
Left:  Contact cement has been placed on the bottle between the marks and on the base of the fin.

Right:  The fin is visually aligned and pressed into position.
Left:  This is a view through the bottle of what an installed fin looks like.

Right:  The photo show the strength and stiffness of the paper fin. The entire weight of the bottle is being held up by the tip of the fin.