Electricity and water are never a good thing to mix, but you never want to be caught out in the dark without a flashlight. Whether you're just a hiker and worried about rain, or prefer to canoe or kayak and are constantly worried about ending up in the drink, a waterproof flashlight is just as cheap and easy to make, as it is to buy.
Disclaimer: Water and electricity are a bad combination. It can short out your equipment, and depending on what it is it can give you a decent jolt. While I have made and tested this flashlight take everything said with a grain of salt and some common sense. Always be careful when putting dangerous elements together.
Step 1: What you need
A few things to consider. Stay away from self sealing tires. They are lined with a slime that is forced into punctures where it will harden. Needless to say, that would become a horrific mess if you try to cut it. If you don't have any tubes with holes in them you could always consider upgrading and then having the old inner tubes to play with, and if you do have a tube with a hole then you of course want to use a section that isn't pierced for this project.
Inner tube from a bicycle
needle and thread
clear plastic bag
Utility knife or scissors
Step 2: Measure twice, cut twice
Any kind of flashlight will do. One that is slimmer will be easier to fit the rubber around, but depending on the type of inner tube, and how well used it is, the rubber will be willing to stretch. Just measure your flashlight, and then measure out a length of tubing about an inch and a half or two inches longer. After that just cut the tube to length.
Step 3: Sealing the back end
Because batteries and water never play nice, this flashlight will need to be sealed up tight. Take the extra inch and a half or so of material on the back end, and glue the insides together. Go ahead and clamp it, wiping up any excess. Airtight is watertight, so if one end is shut, there is less to worry about. After the glue has set, just for some extra insurance I stitched around the edge, staying within the glued area, with a double layer on the inside edge by the flashlight.
Now this could easily be shortened, but I added the extra on so that I could cut a loop for a lanyard or clip.
Step 4: Putting things together
Now we can go ahead and slide the flashlight into the tube. Depending on how big your flashlight is, it can be a good fit, or a little snug, either is okay. For me, the body slid in without much difficulty, although I did have to roll a collar, and then unroll it over the head of the flashlight.
One step I did forget to photograph, and it should be done no later than covering the head of the flashlight. Take the plastic bag, I used a plain sandwich bag, and cut out a small corner. unscrew the head of the flashlight and cover the bulb and the tip with the plastic bag. It should extend past the threading for the head, as when you screw it back on, that will provide extra insulation for the electronics against the elements.
Step 5: Finishing up
Once you have the bulb covered with the plastic, and the head screwed back on, unroll the collar, rolling it up over the head. Trim any excess that obscures the beam, and you should have a waterproof flashlight thats willing to go anywhere you take it.