DIY Polycarbonate hood for 55g

[chkltcow]

Well, my first contribution here.... here goes. I bought a cheap "Top Fin" kit from Pet Smart not really knowing any better a while back. It came with a cheap crappy hood and REALLY crappy lights.... 2 18" 15watt flourescents. The top has has a divider down the middle with 2 ~23 1/2" hoods.
Over the weekend, I bought a 48" dual tube light to put on it. Well, needless to say, it couldn't get any light through the little windows on the top of the included plastic hood. I decided it was time to build my own hood, and plexiglass would be the best way to hold it up and still get the best light transfer. My first plan with a piece of 3/32" plexi from Lowes worked, temporarily. It was too thin and sagged under its own weight. It also required me to remove the whole piece of plexi to access the tank for feeding or cleaning... I had no way to hinge and open it. So after locating a source for the plastic hinge I needed and getting a blade suitable for cutting 3/16" plexiglass.... here we are.

For Americans, you can get the hinge piece (and the polycarbonate) from McMaster-Carr ( http/www.mcmaster.com ). The part number for a hinge for 3/16" polycarbonate is 1793A62 at the bottom of page 2813. Keep in mind that shipping will be expensive because it's a 6' long section shipped in a large heavy tube. No way around that

Standard disclaimers apply... wear safety glasses, don't put your fingers near table saws, use a push stick with a table saw, etc etc... measure twice, cut once.... you get the picture.

First, for cutting plexiglass you're gonna need a fine tooth blade on your table saw. I've heard you can do it with as little as an 80 tooth blade, but I bought a 200 tooth blade. Carbide tipped would be nice, but I managed to do it with good clean cuts with a normal steel tooth blade. Should be common sense, but LEAVE THE PLASTIC ON THE PLEXIGLASS WHILE WORKING. Measure the opening on the top of the tank and cut your pieces of plexi to fit. If you have air hoses, a skimmer, a hang on filter, thermometer, etc... you're gonna need to make holes for them too, but you can worry about that in a second. After cutting your piece to fit, you should have a nice piece that you're ready to "test fit".

 

[chkltcow]

Next step.... after you test fit it, if you have any of the mentioned hoses, filters, etc in the way... obviously it's not gonna go. Mark where they are and measure how much room you'll need for those cuts. Mark these so you'll know how deep to cut in. For me, it was 2" deep

 

[chkltcow]

Set your rip fence and cut the notches that way. Plexiglass cuts best if you have the blade only about 1/8" above the top of the glass, but you're gonna have to raise it more for these cuts or else you'll take too much out of the bottom of the glass due to the curved nature of the blade.

After you've made those cuts, turn your plexi around and line it up with the blade as if you're gonna cut straight down between those two notches. Lock your rip fence at that distance.... then crank the blade all the way down.

 

[chkltcow]

At this point, the blade should be under the surface of the table, not in contact with the plexi. Move the plexi so that the blade will come up through the plexi along the cut line you want. Turn on the saw, and use the crank on the front to raise the blade up through the plexi until you've met one of the notches. BE CAREFUL with this. Most likely , your blade will be spinning the correct direction to sling very hot particles of polycarbonate right onto your hand on the crank. It's not comfortable, so stay out of the way of it as much as you can.

At this point, if you don't have a splitter on your table saw, you may be able to slide the plexi along the rip fence and finish the cut to the other notch. If not, not a big deal... you'll just need to take a fine toothed hacksaw and finish the cut.

 

[chkltcow]

At this point you should have a nice clean cutout that's able to clear all your filters and other devices on the back. Of course, if you were just doing a space for a small thing like air hoses or a thermometer, a simple drill or a holesaw would have done the trick. If you use a holesaw on plexi, make sure it's a thin blade with fine teeth, not the typical coarse thick blade for doing wood cuts. Test fit on your tank and make any adjustments now.

 

[chkltcow]

Once the plexi fits where you want it to, put your light back on top and mark the cut for the hinge. Come out just a bit in front of the light right to make sure you have room to clear it, but don't come out too far or you're gonna cut down on space you have to get your hand in the opening.

Take it back to the tablesaw and cut it right down that line.

 

[chkltcow]

Slide the hinge piece on both pieces of plexiglass like they'll eventually be. Again.. put it on top and test fit. Keep in mind that during this test fitting, the hinge will slide on SO much easier with the protective plastic still in place.

 

[chkltcow]

And now it's time for the final details. Measure and mark where you want your handles to go so you can drill the holes for it. Clamp a piece of scrap wood on the backside of the plexi to prevent chipping as the drill bit passes through. Drill slowly to prevent cracking.

 

[chkltcow]

And finally, test the handle in the hole/holes.

Once you're sure it fits well, you're done. Take the handle off, rip off all the protective plastic, slide the pieces back in the hinges, and put the handle back on. You're ready to put your new hood on top of your tank. Put it on top, put your light in place... and look at the amount of light that makes it through to your plants and fish

 

[chkltcow]

And finally pictures of the finished product:

Total cost for the hood was about $50, mostly due to the cost of shipping for that cheap hinge All in all, it tok me about an hour to figure out what I was doing and actually build it. I think it was well worth it to get something between my light and the water that still provides just as much room to get my hands in to work as the stock plastic piece did... and clear enough to allow that wonderful light transfer from those 48" bulbs. It actually turned out looking really nice, I think. I like the simplistic black and clear look more than I do fancy wood canopies..... at least where my aquarium sits.

 

[fufanu360]

wow u did an awsome job guy!!!! i made my hood out of plexi glass too but its all bowed from the weight of the light , how did u get urs not to bow??

 

[chkltcow]

The light is actually about 1" longer than the tank itself, so it rests up on the tank frame.... not on the glass.

 

[chkltcow]

Oh, one last step I forgot. Use the back side of a knife, or a closed pair of scissors, or some other object for scraping each of the cuts you made to get rid of any excess hanging pieces of plastic. Most table saw cuts should be very clean, but if you had to use a hacksaw for anything, there's likely ruffed edges there. Don't use the blade, use the blunt side... and just scrape down the edge until it's smoothed out.