.::. Fins : Making

Creating a water rocket fins out of PETE plastic, that are durable and aerodynamic.

First, I would like to thank Robert Youens for the inspiration on these fins. He made his out of paper but I'm making these out of PETE. It's more durable as they crash straight through trees on their return trip to Earth. Check out his excellent guide on this page.
This page will be describing how I create four, structured, fins out of a single PETE 2 liter bottle. These fins are very durable, and aerodynamic in shape. It takes a while to build them but the results are well worth it. You'll need one 2 liter bottle, a knife, scissors, a 12" ruler, a Sharpie brand pen, and some packaging tape. Please read all instructions before cutting your plastic. I really mean it. Read through all of this mumbo jumbo so you don't mess up. A bottle is a terrible thing to waste.
	Here we are with our victim. I've got all of my supplies together and we're ready to operate. Don't worry. The bottle won't feel any pain during the operation.
	I've taken my knife and started a slit and then switched to scissors to cut out the "flat" portion of the 2 liter bottle. The top and bottom of the bottle is scrap. You'll end up with a rectangular piece of PETE bottle that we're goint to turn into our four fins.
	Here's the top and bottom of the bottles. You could keep them and use them for various other purposes such as in parachute deployment or as a funnel for creating FTC moulds. The only limitation is your imagination. Now, back to creating our fins.
	I fold over our sheet of plastic long ways and then cut it into two equal sized pieces. It might actually work better if you just mark the half way point with the Sharpie, draw a straight line between them and cut it with the scissors.
	Here's another view. I've folded the piece in half and I'm preparing to cut it in half.
	Here, I'm cutting the plastic that I've folded in half. You could just mark it and cut it.
	I've got two approximately equal pieces of the PETE plastic. I'm now folding over one of the pieces and I'm going to make two fins out of this piece.
	I'm using the ruler to press down on the plastic to get a good crease in the pastic. It's not easy to do actually as some good pressure is required. I also mark the plastic with the sharpie half way through the plastic. The sheet is 5.5 inches wide so I can create two 2.75 inch fins from this.
	I have drawn all of my lines. Notice that I have marked 0.5 inches in from the fold of the plastic. I'm going to use my scissors to cut the fin. Notice that the "short" end of the fin is the side with the fold to it. Don't mark the plastic with the short end of the fin being the open side. It helps to get a good hold on the open side while cutting. The plastic will want to move on the upper level more than the lower level of plastic as you are cutting. Holding it tight helps prevent this and gets you two good semetrical pieces. Don't ask me how I know this, I just know it, all right!?!?!
	We're now going to use pieces of the packaging tape to tape the leading and trailing edges of the fin. The ruler helps use get a good crease of the plastic and keep the edges together as we're taping.
	With careful application of the tape, you won't get many air bubbles in the tape. Tape one side then flip the fin over and fold in the tape onto the other side of the fin.
	This fin is fully taped. It's hard to see since it's blurry but it's a fully taped fin. The hardest part is over.
	Here's another look. You can see the packaging tape in this picture on the leading and trailing edges.
	In this picture, I've marked a spot 0.5 inches up from the open end of the fin. We'll use those marks to fold open the flanges.
	I press the ruler down along the marks and fold up one side of the flange. I then remove the ruler and then fold the plastic over some more. Once the fold is begun, it's easy to fold it over and get a good flange.
	Here's our fin almost done. The flanges are folded out on each side and will make a good base to glue to the rocket.
	These fins will have structure to them. To get the fin into a more aerodynamic shape, cut a slit half way down the flange. Repeat on the exact opposide side. Once we do this, the fin can flex open.
	Here you can see that the fin can now flex open to take our spar that goes inside.
	I've taken some of the scrap pieces of plastic and I've cut them down and made them thinner. We'll use them as the spar on the inside of the fin. I've also flipped over the fold so the plastic flares to the outside making a "V" shape.
	I slip in the spar into the fin and it holds open the fin. This fin is done. I now make three more of them from the other pieces of plastic. Make sure to keep all of the fins symetrical in size and diameter.
	Here's another view of the fin sitting on the table.
	You can see the shape of the fin. Narrow at the tip, wide at the base. These fins should really help the bottle fly straight.
	Here are a picture of all of the fins, all taken from one 2 liter bottle.