Plywood + Acrylic Idea

[earthstudent]

I am planning a 600g (or around there) tank and I have been going through many of the plywood builds here. There are some great builds by the way. I was planing on going with a 2x4 outer frame with 1/2 or 3/4 plywood inside I am trying to figure out the best way to waterproof the tank and have it last basically forever or long as I live at least, if that is possible.
I see most people are using liquid rubber, polyester resin or epoxy resin. I was thinking of epoxy using some sort of fabric and building it up to a good thick layer.
I also saw someone mention of the possibility of using laminate counter top sheets adhered to the plywood and caulking the joints with silicone. But apparently the laminate is not completely waterproof. This idea however got me thinking. It would be easy to cut some sort of sheet to size and seal the corners with silicone.
I was thinking about thin sheets of acrylic (1/8" or 1/4") on the inside of the plywood sealed at the joints with acrylic cement or silicone. Like making an acrylic shell on the inside of the plywood tank relying in the wood for support. And using a 1" thick piece of acrylic for the viewing window(I am planning a 24"-30" tall tank). I would still epoxy the top edge (or bring the acrylic over the edge) and outside of the tank.

Does this sound reasonable? Has anyone tried this? Or would several layers of epoxy and fabric, be easier and better?

And has anyone seen these. Looks interesting to say the least.
http://www.aquaticeco.com/subcategories/2080/Fiberglass-Tanks-With-Window

 

[BadOleRoss]

I did this several years ago (20+/-) on a tank that was about 375 gallons. I framed the tank using 2x4s and lined the inside of the frame with plywood and 1/4 acrylic. The front viewing window was 1/2" acrylic. I then caulked the seals with aquarium silicone. The tank lasted for about 3 years before I noticed a leak that had rotted the wood. The leak came from 2 center bottom drains that I had attempted to install and then had to patch the holes. This was long before the Internet and bulkhead fitting were not available, I dried to use sink drains! Didn't work! Anyway, the downside to you plan is that silicone reportedly does not bond that well to acrylics......but it worked for me! The tank I am currently working on is sealed with liquid rubber and will have a glass viewing window. Getting the glass to seal to the liquid rubber has been a bit of a challenge but I think I have it figured out. I will know soon!

 

[ITHURTZ]

inner shell would work, but ur measurements would have to be exact. I have 3/4" windows on my 330 i see no reason why u need 1"

 

[Pharaoh]

I would have to know the dimensions of the tank to figure what thickness acrylic you would need.

But, there has also been talk of using black or white ABS plastic that is sealed together with GOOP. There are tons of ways to do it.

 

[ITHURTZ]

What about PVC sheets? 4x8" 1/4" for 130$ Then just get some pvc glue and melt them together. If there are problems with corners like that throw on a pvc angle for the corners and slap it on no?

Gray PVC 4x8 1/8" 60$

 

[wednesday13]

you can also heat weld the seams together with a plastic welder. I am doing this on a 650 with polypropolene sheets. Johnptc proved this method with his 800 growout.

 

[CJH]

I was thinking of epoxy using some sort of fabric and building it up to a good thick layer.

I also saw someone mention of the possibility of using laminate counter top sheets adhered to the plywood and caulking the joints with silicone. But apparently the laminate is not completely waterproof.

If you want to use fiberglass fabric and a resin to build up a thick layer then I'd look at polyester resin simply because it will be cheaper to wet out all that cloth. Epoxy is better, IMO, when you're trying to avoid or minimize that cloth to begin with.

For sure don't use laminate. There was a good discussion on this not too long ago. I just don't think modern laminates are up to the task.

If you're going to use some sort of solid plastic sheet to line the inside then you need to make sure it can be solvent welded or that silicone or some other sort of fish safe adhesive will stick to it. Anything thick enough to be thermally welded will be very expensive.

One issue with solvent welding is that it's very difficult to get perfect joints from panel to panel if you're dealing with an irregular framed plywood carcass. Solvent welds (like how acrylic tanks are built) require much tighter tolerances than that. It certainly can be done but I like the idea of using some sort of gap filling adhesive that doesn't require perfect joints.

One thought is to line the plywood carcass with solid PVC sheets as previously mentioned and then overlapping all the interior corners with PVC angle welded into place with one of the thicker PVC solvents. You'd then only have to worry about the small gaps that would occur where the angle met adjacent sections.

But by the time you went to all the trouble I have to wonder if using some sort of liquid sealer wouldn't have been cheaper and easier? Shipping on full size sheet goods is very expensive so if you can't pick it up locally it might end up costing too much.

Just for the PVC plastic mentioned you're up to around $2 per square foot before shipping. A lot of liquid sealers come in well under that amount.

 

[earthstudent]

I really like the PVC idea using corner angle, solvent welded to all the joints. If I were to use corner angle I could go with fairly thin sheets.
I was thinking of the same thing with acrylic as you can get acrylic corner angle and use something like weld-on 16 to weld all the joints.
I was also thinking about ABS plastic as it is very cheap and is used for showers and tubs and I could just silicone all the joints so a "perfect" fit would not be required. This option is actually just as cheap if not cheaper than epoxy paint.
My question is... would epoxy be just as good, and last as long?

 

[CJH]

I really like the PVC idea using corner angle, solvent welded to all the joints.

I was thinking of the same thing with acrylic as you can get acrylic corner angle.

I was also thinking about ABS plastic as it is very cheap and is used for showers and tubs and I could just silicone all the joints so a "perfect" fit would not be required.

My question is... would epoxy be just as good, and last as long?

The acrylic corner angle I have seen is not as flexible as the PVC angle I have seen so it might be harder to press into the corners for a perfect fit.

ABS is a type of styrene so you can use the corner angle idea there as well as I have seen styrene corner angle on lists but never handled a piece myself. I have heard that ABS can become brittle after long periods of submersion but if the tank it built well this shouldn't matter.

Again, shipping on full sheets is going to be expensive so you should consider seeing what you can get local or at least "close". If you shop for PVC make sure it's solid PVC and not expanded PVC like you see for sale in sign shops. It's basically foamed PVC with two thin layers of solid PVC on each side so your actual waterproof membrane is very thin.

If you want to use silicone or some other fish safe caulk for the corners I would try to figure out what plastic it forms the strongest bond do.

As far as comparing the cost to epoxy or polyester, that really depends on whether you use fiberglass cloth which requires a lot more resin as well as more difficulity.

You mention both epoxy and epoxy paint and I want to stress they are two different things. Without going into a lot of detail, you should not use epoxy paint to wet out anything but the lightest fiberglass cloth or rovings. The thicker cloth, roving and mat should be wetted out with resin.

A plastic lined tank if done well should be very long lasting. Thinking about it some more, using silicone or another caulk for the corners would make for a greater degree of repairability than corner angle. So if you go that route I would really research what caulks for the best bonds with the plastic you'll use and which are fish safe, of course.

 

[earthstudent]

If I were to go the epoxy rout, I would be using cloth on all surfaces, not just the joint areas. This would be a lot of work (and cost) and not the easiest thing to do but definitely doable non the less. I am definitely leaning towards lining with sheets of some type of plastic that bonds to silicone well and joining/waterproofing the corners that way.
It looks like The plastic lining method will be easily repairable. Even if a panel cracks it could be taken out and replaced. Easy to install, just get the cuts accurate and the silicon will take care of the rest. It also looks like it would be cheaper. I guess at this point I am trying to find the cons? Oh, and I may be able to get the material local as well.