DIY Lexan/polycarb top

[mattroth54]

I was about to pull the trigger on a Kraken/TopLid type top for my 109g 20x60. The $500+ cost was doable and would have looked great, but the cheap part of me thought there’s a better way. After considering a RedSea kit and a few other options, I decided the higher end, solid built product was what I wanted. I also realized my other hobby, woodworking, gives me a wonderful shop, with nice tools that can probably also cut polycarbonate with a few minor setup adjustments. Plus, I enjoy my time in the shop.

So it starts: I found a local plastic shop to source a couple pieces of 3/8” lexan. I’ve made some supports on the 3d printer to cover the tank until I get some shop time to make the cuts for the spline and netting.

The plan is to cut a rabbet around perimeter, so the lexan sits inside the rimless tank. I’ll also cut the inside and stretch 1/4” mesh. I think I can complete this for about half the cost of a commercial top.

In the mean time, the fish are going to have tougher time escaping.

I’ll keep the post updated on progress.

 

[Kooma]

Nice! I’ve wanted to build a top for mine, but I run the top of my tank almost fully sealed. Large glass pane (old glass table top) is the majority of it and no sagging which is nice. One day I’ll bump it wrong and send 40lbs of tempered glass into my tank, I’m sure.

Following along. May top was mostly to save $ on heating. I cut my energy usage and evaporated in half with the glass top, and still maintain a 8-8.1ph.

 

[JTP424]

Following... curious as to potential warping....

 

[cba191]

Whats the best way to cut polycarb? I need a lid for an ato.

 

[mattroth54]

Following... curious as to potential warping....

It's the same material, 3/8" Lexan, aka polycarbonate, that seems to be used by many the big boys. I'm still working out the details of how much material I'll leave around the perimeter. Looking at pics of similar tops, it looks like most use 1.5-2". I'd be curious if anyone is willing to share the dimensions on their professionally made top.

 

[UncommonSense]

Whats the best way to cut polycarb? I need a lid for an ato.

It can be sketchy… the polycarb likes to “grab” the tool, and crack/throw shards!

Triple chip high tooth count saw blades designed for plastics do work!

— I like to cut close to final dimensions, then trim to final dimension with a router! (Don’t consume more than 50% of the router bit’s thickness per-pass for safety reasons!)

 

[mattroth54]

Whats the best way to cut polycarb? I need a lid for an ato.

I'm planning to use a handheld router and templates to cut the spline channels and cut out the centers. For the rabbets, I'd like to use my carbide dado stack on the table saw. TBD if it makes a nice cut on the Lexan. A 1/2" single flute carbide upcut router bit on a table router is my backup if the dado gums up my test piece. For a simple, straight cut, a fine tooth crosscut table saw blade should do the trick.

 

[UncommonSense]

It's the same material, 3/8" Lexan, aka polycarbonate, that seems to be used by many the big boys. I'm still working out the details of how much material I'll leave around the perimeter. Looking at pics of similar tops, it looks like most use 1.5-2". I'd be curious if anyone is willing to share the dimensions on their professionally made top.

Here’s a pair of custom lids by Kraken, on a local reefing buddy’s tank, for reference!

The tank is right around 60”x24”x16”… the perimeter of the lids are probably 2.5”-3” wide!

(Pro tip to improve over Kraken? — spend the extra time routing all the sharp 90 degree corners down to a tiny 45 degree bevel!)

 

[mattroth54]

Here’s a pair of custom lids by Kraken, on a local reefing buddy’s tank, for reference!

The tank is right around 60”x24”x16”… the perimeter of the lids are probably 2.5”-3” wide!

(Pro tip to improve over Kraken? — spend the extra time routing all the sharp 90 degree corners down to a tiny 45 degree bevel!)

This is certainly my inspiration. I thought the feed cup is 2.5". I plan to 3d print one of those for each front corner. I'd love an exact measurement of the permitter on that cover. I'll def either round over or bevel the edges. No way something would leave my shop otherwise!

 

[UncommonSense]

I'd love an exact measurement of the permitter on that cover.

I’ll see if I can get those! I’m not over there too often these days; the tank doesn’t need much after all the setup!

I'll def either round over or bevel the edges. No way something would leave my shop otherwise!

As it should be!

 

[mattroth54]

And for the record, without already being spoiled with a really nice woodshop, there's no way DIY this project would make any financial sense. The companies like Kraken/TopLid/etc. are a bargain for what they offer. The material is pricy as is...the shop that sold it quoted me about $800 for the cutting. I'm just seeing this as a fun opportunity to bring a couple of my hobbies together.

 

[Ironwill723]

Please keep us updated on how it goes...I am thinking of giving this a go as well.

 

[mattroth54]

Please keep us updated on how it goes...I am thinking of giving this a go as well.

Might be a week or so before this winds up in the shop.

 

[mattroth54]

Update:

Had some time to get things underway. Was able to cut the rabbets to allow the cover to drop into the top. Woodworking dado was a bit grabby and chippy, as expected. A couple passes with a spiral upcut bit on router table did nice job. Not as smooth as I’d like, but at eye level, it looks great. Also managed to get the centers laid out and cut. Again, a small spiral upcut bit on handheld router with template cut the lexan quite nicely.

Next up: route channels to hold spline, cutout for AFS’s, and bevel/finish edges.

More to come!

 

[mattroth54]

Here’s the template I used to cut out the centers and route the channels for the spline. Got them all done tonight. Finished pics to come tomorrow.

 

[Ironwill723]

Excellent job. What bit are you using to make the spline channel?

 

[mattroth54]

Excellent job. What bit are you using to make the spline channel?

Thanks! 1/8” spiral upcut. Same one used for cutting.

 

[mattroth54]

All done! Overall, I’m super happy how it turned out. It definitely has marks of someone new to machining polycarb, but not bad for first go at such a project. The cutouts for my two AFS turned out better than expected.

I’ll try my hand at drawing some feed hole covers/cups on the 3d printer.

Final take, touched on earlier…the seemingly high prices charged by the top companies in this space are very fair for what you get. I don’t have anybody in my shop that’s a paid expert at any of this, they do. I have nice, expensive equipment, but nothing like a cad based cnc equipment/etc. If any of my tooling decided to grab one of these cut sheets and throw it across the shop, I’d immediately be at the cost of just ordering an top and having it made.

All that said, I really enjoyed this project as it was a nice combination of two hobbies. Happy to provide any insights or share insights if anybody wanted to take on a similar project.

 

[mattroth54]

Easy enough to make a feed hole cover.

 

[ShakeyGizzard]

I used this as a template for my 20G and 40B tanks. I like the 2 piece design I used on the 40B so i am using it for my 20G

20 Gallon