Water Rockets - Fins

Fins made from CD ROMS

I decided to have a go with the junk mail CD ROMS that many of us get from time to time - this is recycling at its best. CD ROMS curtesy of AOL (two plus another experimental one) and Compuserve (one) {Is this free adversising for ISPs or is it a demographic analysis of who sends what through the post?}.

To cut a CD ROM, you should not try the score and bend method (we tried this and all that happened was the thing shattered - breaking anywhere except along the score line). It is possible to use a saw to cut along the green line on the diagram on the left but I found that a soldering iron did the job very well. I scored the line and then cut it, slowly and carefully along the score line with the tip of my 15 Watt Antex Model C soldering iron with a 3mm bit. Once the 3 CD ROMs are cut, they need a slot cutting in them (that is just big enough to fit a cable tie) and for this, whether you used a soldering iron to do the initial cut or not, is best done with the soldering iron. Simply lay the CD ROMs on top of eacf other and use the hole in the first one to mark the rest.

Fixing the fins

Fix a short skirt onto the bottom of the rocket so that it protrudes just a little further than the end of the nozzle. Tape it and put some tape along the edge of the skirt so that you will not cut yourself on it in the field.

Through each of the fins, pass a cable tie. Put the end of each cable tie through the rachet of the next so as to form an oversized ring with the fins threaded onto it.

Tighten up the cable ties until they just hold onto the skirt on the rocket. Put gaffer tape onto the cable ties so as to hold them in place and then run gaffer tape down the join between the fins and the skirt.

Cut the ends of the cable ties so that they don't go over the edge of the CD ROMs and then tape these to each other so that the cable tie ends hold the fins at the right angle.

Finally, put down some extra straps of tape around the fins to stablalise them.

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Fins made from the side of a pop bottle Fins mounted on an aerodynamic skirt