My Fish Tank by Lam Nguyen

Parabolic Reflector

To build this parabolic reflector you have to be a bit handyman and have proper wood work tools as well as software tools. Let take a look at what is this parabolic and see if you can do it.           The first thing to do is to design the parabolic shape and find the right focus point. There is a software program that would do this but I lost it.

The equation for a parabolic shape is X square = 4pY (again open your physic book and confirm this. I use Calculus with Analytical Geometry book that I have in my book library page 455) where p is the focus point. I wrote a Quick Basic program to generate the X and the Y points and write it to a text file with a coma delimiter. Then I use Excel software to import the file and draw the parabolic shape on the computer for initial shape determine. What we want is to determine the final width and the focus point of the parabola that will fit inside the cover. Once you done that then manually graph this data on a graphic engineer paper. I found a software program that would generate a true size engineering grid on paper. You can set it to print out a 1 inch grid with 10 little mark per inch. The software name is "agrapher". You have to search the Internet and down load it. It will made your graph much more accurate. Once you did the graph of the actual size of the parabolic, you need to tape it to a piece of wood about 1/4 inch thick using spray on adhesive. Then either use a cope saw or a jig saw to cut along the shape, be precise about it as this is the model for the rest of the pieces. Then you need to use a router to duplicate the rest of the pieces or ribs as I called it using this model.

Once you got all the ribs that are needed (8 ribs per 4 ft length sound good to me), then you would glue them to a 1/2 inch by 4 ft long base in a nice and straight line using wood glue and nail. Wait until the glue is cured then use 1/8 inch thick sheet of wood to made a skin on the inside of the ribs. ( A pneumatic nailer -18 gauge would be handy here).                    Now for the reflective material you can use the Mylar blanket and spray adhesive to finish the job. Then you have a hand build parabolic reflector, imaging the capability of that reflector, it will shine light into your fish tank like a sun and the added bonus is that it only consumes 80W of power. Compare that to 2-175W of metal halides plus 2-40W artinic. (ok it come close to comparable. But hey there is no heat added to the fish tank and the cost of operating it is cheap).                    I went as far as design the model and get the ribs cut for a T12 bulb at 3/4 inch focal point from the center of the T12 bulb to the back of the reflector. At that focal point, the reflector width was about 5.5 inches. I have only 12 inches total width space on my fish tank. So 2-40W with 5.5 inches width per reflector would give a nice complete coverage with evenly distributed straight down rays of light across the tank width.

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