| Today we're making a jig to help us get our fins glued onto our bottle. One thing that is a constant frustration in water rockets is looking for a fast drying glue, that really holds to the slick plastic. Holding fins to the bottle while the glue dries gets old really fast. A jig will do the holding for us, keeping the fins aligned while the glue takes it's time to dry. The OD of the box is about 4.25 inches. |
 |
I've found a corrugated cardboard box that is just slightly smaller than the diameter of the 2 liter bottle. I want it just slightly smaller so that it "curves" around the bottle a bit and will press the fin flanges to the bottle as the glue dries. |
 |
While our box is the right width, it's too long. No problem. I'll just shorten it a bit. I use my angle to draw two 45 degree angles across the box. These lines will also be used to find the exact center of the box as well. More on that later.
|
 |
In this picture, I'm using the angle to create the line at 45 degrees from one corner to the opposite wall of the box.
|
 |
You can see my angled lines and one line that squares off the box where the diagonal line meets the walls.
|
 |
With a pair of scissors, I cut through the walls of the box and create one part of our jig.
|
 |
With a little more work with the scissors, I've cut down the other part of the box to be a mirror image of our first box. Fitting these two pieces together will give us a thick wall that will help hold the fins in place.
|
 |
The two box ends will slide together to make one box that the bottle will fit into.
|
 |
Here are the two boxes nested inside each other.
|
 |
Here's the top of the boxes. I think I'll remove the flaps. They'll just get in the way.
|
 |
Duct tape is your friend when it comes to cardboard.
|
 |
The box is ready now to have the slots for the fins cut into it.
|
 |
But first, we'll use a saw tipped drill bit (the kind used to bore out a hole for a deadbolt lock in a door) to drill out spacing for the throat of the bottle. This hold is big enough for the bottle, and the circular shape will help keep the bottle centered while the fins are glued on.
|
 |
Here's where those 45 degree lines help me find the exact center of the box.
|
 |
Here's the box with the hole drilled out for the throat of the bottle.
|
 |
A test run of the bottle. I will mark the bottle with a pen. This will help me decide how deep to cut the slots in the box so that when the fins are slid in, they don't get into the area of the bottle that starts curving.
|
 |
With this box, about 2.5 inches did the trick. I used a sabre saw to cut the slots but scissors or a utility knife would have done as well.
|
 |
I cut my slots on a slight angle. Each of the four angles, I tried to cut them at exactly the same angle. This put the fins at an angle, and get the rocket on a good spin during launch. Getting the spin on the rocket helps stabilize the flight.
|
 |
We're looking good. A few slight adjustments to the depth of the cut to the slot and we're ready to give it a try.
|
 |
Here's a dry run with the fins in the jig.
|
 |
This time, I'm using PVC cement to glue the fins to the bottle. By pulling on the cardboard, I can slip in the fins into the jig without getting glue all over the length of the bottle as I slide the fins into place. I stand the bottle on its end on a shelf and I can come back tomorrow when the glue is dry. This jig has been a huge time saver when creating rockets.
|
