Taking a cue from one of Cory's recent DIY videos, I decided to replace my haphazard lid collection with some polycarbonate panels. I had glass tops on most of the tanks, but usually only one strip because the huge hinge you get with the top messed with where I could put the light and blocked a bunch. That left a lot of open water, and I was getting a lot more evap than I wanted, so...
Preparing to make the first cuts. I used that cordless Ryobi 5 1/2 inch circular saw, although I did get a new blade with 100 teeth on it for this project. It's light, I have lots of extra batteries, and for this job, it worked great.
I made that wood guide because I was too cheap to buy a metal guide. It works for cuts on either side of my blade. I just clamp the edge down on the line I want to cut, push the saw up against the lip (there is a 1/4 inch gap there now you can see just over the handle, normally that's tight to the wood), and cut away. No more measuring 4 and 3/8" inches over to clamp a straight edge down. It worked like a champ. (h/t to Family Handyman for the idea)
I made 5 lids in this session. the largest was for a 40B. I also made each lid a single piece (for the moment anyhow). You can see that on the 40B, there is a little bowing in the middle, so the edge sticks up just a bit. When the front edge is pushed back off the aquarium rim lip, it bows much more. I wouldn't go more than 36" wide when using this material. Also, measure twice, cut once! 4 of the 5 fit perfect first time. The fifth I got a little slack with the accuracy, and the first time cut it too short. I overcompensated when cutting a new panel and made it an 1/8 too long, so I trimmed a blades thickness off and it dropped in over my 20L pretty well.
The sag is not really all that noticeable in the Full tank shot. Next up are knobs. Also, I did these last weekend, and after a week of living with them, I think I'm ordering/buying some clear plastic hinges and cutting each sheet in half lengthwise to make hinged lids. The single sheet is a bit unwieldy for feeding or quick access to the tank. Thanks to Cory for the video and inspiration.