This year we made "surprises" again for our Dutch "Sinterklaas" celebration. I wanted to make a life-size "hamster ball", inspired by the balls we rented last summer for our camp-activities. Then the boy I draw for the "surprise" (it is a kind of secret Santa, I think) wanted to have dodecahedron dice, so that made my plan even better. The result would be a huge inflatable dodecahedron dice where you can get into.

My biggest problem was to get the right foil. I finally found thick, transparant PVC at a local store, that is used to put over a table so it can't get stained.

The maximum size was dictated by the size of my heat-seal machine. This machine is for closing bags for in the freezer and has a width of 30 cm (12 inch), so that makes the maximum length of the ribs of the dice 2 x 30 cm = 60 cm (24 inch).

This gave me an inflated object of approximately 140 cm.

Step 1: You Will Need

Materials:

thick PVC table protector foil
vinyl sticker material
some kind of tube or hose
big piece of paper or cardboard

Tools:

a machine to heat-seal plastic
scissors
ruler (or piece of wood or something)
tape measure
marker (sharpy)
clothes pins or something like that
a vinyl cutter or somewhere where you can use one
a (air matras) pump

Step 2: The Design

The dodecahedron was a good design for the heat-sealer I have, even if I would have wanted to make just a ball.

This form makes a big ball with relatively short ribs.

Draw a pentagon on a piece of paper with a maximum rib length of twice the length of your heat-sealer.

Don't ask me how to draw a pentagon, because I had a lot of trouble with that. Luckily you can find clear instructions on the internet when you google for "drawing pentagon".

I used a dice as my guide. From this dice I made a design for what pentagon I will make already connected, to make as little seams as possible.

In total I ended up with only 3 parts of 4 pentagon each.

On the drawing you can see what pentagon will be connected to what other pentagon and where the other pieces must go. This drawing was very important to keep track of everything.

You can see that where 7 should go to 9 I drew extra long lines on the site. Here we will make the entrance into the ball.

Step 3: Cutting the PVC Foil

For the ball that I made with 60 cm ribs, you will need 10 meter PVC with a width of 140 cm. (this costed 24,- Euro)

Use the drawing on the piece of paper, to transfer the design to the PVC foil.
Connect 4 pentagon together like on the drawing in the previous step.
Use the scissors to cut 2,5 cm (1 inch) around the drawing.
On one side of pentagon 7 and one side of pentagon 9, we will leave a piece of PVC as big as possible. (See the drawing in the previous step)
Cut in, in the corners until the line (see picture).
Do this three times.
I also drew on each pentagon the number from the dice and on each line to what number it should connect.

Step 4: Heat Seal the Seams

Clamp two pieces that should go together on top of each other. (You are working inside out!)
Put one half in the heat-sealer and seal together.
Turn your material over.
Seal the other half of the seam. (if you make a small object, or you have a big heat-sealer, you might make a seam in one go)
Repeat this for all seams except the one with the extra big overlaps. (they will become the entrance)
Put the big overlaps on top of each other and make a seam straight out from the corner of the pentagon, on each side.
Cut the tunnel that you created with this overlaps clean.

Step 5: Inflate the Ball

Turn the ball outside in, so the seams go on the inside. (this is not very easy)
Role the entrance tunnel closed except for one corner, where you put the tube in.
Use the clamps or clothes pins to keep the tunnel rolled up and closed.
Put a pump on the tube.
Inflate the ball. (My pump takes 12 minutes to inflate the ball)

You will probably have small holes on all the corners. We will fix that in the next step.

Step 6: Stickers

I designed a sticker in Illustrator to put over the holes in the corners.

Cut 20 corner stickers. (I also cut the same corners for the two corners next to the entrance tunnel, but I than cut off one arm with my scissors)
Stick the stickers on the corners.

The stickers will crease a bit, because the surface isn't flat.

The stickers will plug the holes and make the ball stronger.

For my dice-design I also cut the numbers 1-12, but that was just esthetic.