Just a little boredom-buster - a paper version of a reaction turbine that will keep the wee'uns out of your hair for a while on a wet afternoon.

_{(Yes, I know it's Summer, yes, I know it's some of the hottest weather the UK has had this year, but this is the UK - we could have snow tomorrow.)}

Step 1: What You Need

This is a really simple make, so you need really simple stuff:

Glue - a glue-stick is quickest, but PVA is stronger. Just use what you're happiest with.
Scissors (a craft knife would be handy as well, but is not essential).
Sticky tape.
A straw.
The template - either draw one yourself from the photos, or print out a copy of the template to use yourself. If you're printing, put two on a page to make them the same size as this. If you're drawing, the squares in the photo are all 1cm across, and the final turbine is 5cm square.

Step 2: The Template

The turbine is basically a box with holes in.

If you're following my version, you cut along all the solid lines, and crease all the dashed and dotted lines.

If, like me, you like to be able to see the construction lines, then mountain-fold all the dashed lines and valley-fold the dotted lines. If you prefer not to see the construction lies, then do the opposite.

If you want to decorate your turbine, the do it before you cut it out - trust me, it's easier that way.

#1 son wanted a propeller draw on the side he could see (to play helicopters) and a spiral on the side he couldn't see (to try and hypnotise #2 son).

Step 3: Making the Turbine.

When you have cut out the pieces, they need holes in the middle.

You can use a knife to cut an X, or a sharp pencil to poke a circular hole, but the exact size depends on your straws. The hole should be small enough to cut air-loss around the straw, but large enough to stop friction spoiling your fun.

Fold up the largest piece. All the creases should fold at 90^o, which means the out-most sections will over-lap each other at the corners.

Glue these corners to make a lidless box-shape, pressing the layers firmly together. If you are using a liquid glue instead of a glue-stick, allow time for the glue to dry slightly. Notice that the corners are open, with the small flaps all sticking out.

Glue around the edges of the plain square section, and stick it to the first section to "close the box". Again, you need to press firmly, so slide your closed scissors in through the corner holes to give you something to press against.

Step 4: Preparing the Straw and Putting It All Together.

Cut two longish strips of paper. The exact size isn't important (I cut a 1cm wide strip from the full width of an A4 sheet).

Tape one end of one strip to the straw, then wrap the paper round and around the straw, taping the other end in place as well. This is to stop the turbine slipping along the straw.

Next to the stop, snip a hole in the side of the straw. Again, the exact size isn't important, but be careful - if it's too small, you won't be able to blow enough air into the turbine to make it work. If the hole is too large, the straw may bend and jam the turbine.

Slide the turbine over the straw until it is next to the stop, and covering the hole.

Make another paper stop one the other side of the turbine to stop it slipping the other way. This is another balancing act - too close and friction will stop the turbine working, too far, and the turbine could move off the snipped hole.

Fold and tape the end of the straw over, to stop the air blowing out the wrong way.

Step 5: Adjustments.

Your turbine may not spin perfectly the first time. There are several possible reasons, all easily fixed:

The vents are blocked - did you open up the flaps properly?
The flaps are pointing the wrong way - experiment with the exact position of the flaps - they can make a big difference.
The straw is too tight in the turbine - give the straw a wiggle, or slide the tip of a knife-blade in between and wiggle that.
The paper-strip stops are too close together - as I mentioned, friction is a killer. Just snip the tape of one of the strips of paper and re-wind it slightly further away.
The hole in the side of the straw is too small. Unlikely, but to adjust it you will need to remove a stop. It's more likely that the hole is too large - the straw will bend and wedge the turbine. There's no cure for a too-large hole, you'll have to use a new straw.

Step 6: Extension

This version is square, but that's only because squares are easy. You could make one triangular, hexagonal, anything you like.

You could make one from two circles of card and add curved vanes between.

Decorate it how you like - think of those spinning toys that seem to change colour as they turn.

Above all, though, this is just a toy. No real use as it stands, although maybe a plastic version could be used as a lawn sprinkler? Maybe you know different, though.

What else could you use it for? If you used a balloon as an air-supply, could the turbine drive a propeller and fly? Or maybe to drive the wheel of a toy car?

More likely, just use it as you made it - as a toy. Just remember, if you blow too hard, too long, you may get dizzy and fall over.

_{So if you've made this and given it to your little brother, keep your video camera handy, just in case...}