I can do it cheaper.... Plywood tank.

[Psychotrshman]

Good morning,
I posted a couple days ago about a custom tank I wanted to make (48"Wx48"Dx30"T and found out the acrylic I have is too thin. (It was free, so no biggie). Determined, I contacted a few companies in the area for estimates on building my design. WOW! For acrylic, 2700 dollars, if I picked it up. For glass, 2000 delivered. Those numbers are far greater than I ever thought it'd be.

I went back to the research and found plywood tanks. The epoxy is kind of expensive, but I have acrylic. Now, with the plywood tank, you only have vision on one side, so I've changed the dimensions. I'm now aiming for 84"Wx24"Dx30"T. I'm thinking I can use 2x4 studs and frame it out like a wall. Use 1/2" plywood for the inside and outside with insulation board in between. I would then line the entire thing by gluing 1/4" acrylic to all surfaces with bonded seams and silicone reinforcement. I would then use glass or acrylic for the front.

Anyone tried this? I googled it and the few links I found had turned in to debates for the best acrylic bonding methods and the question was never really answered. It seems to me it would work since the plywood will hold the pressure.

Would 1/4" acryllic work for a corner overflow box or would the pressure break it? Suggestions on sizing the front panels thickness? With a wooden tank, any special concerns about drilling it and installing bulkheads? Any help or suggestions are greatly appreciated. Thanks in advance. Happy Halllowen and Happy Monday. :bounce1:

[lomo]

Hi
If overflow box is filled with water than there is no pressure which could break the box.

[der_wille_zur_macht]

I would strongly caution you to proceed with caution when outside the realm of proven techniques. Epoxy lining is common because it's effective, hard to mess up, and not really THAT expensive.

I have a 360g plywood tank and spent about $300 on epoxy (from uscomposites.com), which was enough to also do a 75g sump and have about half a gallon left. Your tank is slightly smaller, you might squeeze by at $200 - $250.

"lining" a wood box with acrylic presents all kinds of atypical materials issues. How are you going to seal the acrylic to the wood to keep water from getting in between? How are you going to seal the panels of acrylic to each other? Typical acrylic methods won't easily work considering you have to build it "in place."

For the front panel, I'd be looking at 15mm glass.

Regarding your idea of framing the tank like a 2x4 wall - Assuming you use reasonable quality plywood, it's nowhere near necessary for a tank that size. You could get by with a single layer of 3/4" plywood, assuming the top was eurobraced properly. No need to have a frame or reinforcement elsewhere.

[Psychotrshman]

My concern with epoxy is more than just cost. I've never worked with fiberglass before, but I don't imagine its easy. I've never used epoxy, but from what i read it can dilute into the tank. Also, doesn't epoxy have to be mixed together to work? I just figured since i have the acrylic, I might as well use it. If you use 3/4" plywood, do you have biscuit join it or just screw it? What is euro bracing? Thanks for all the help. :)

[BeanAnimal]

Epoxy "dilute into the tank"... that is a new one. Epoxy is an inert polymer once it is set and will not leach chemicals into the tank.

Working with resin takes much less skill than working with acrylic.

[Psychotrshman]

It sounded odd to me too since dried epoxy is almost like plastic. But there was an article (i wanna say it was on reef tank) that said not to use epoxy resins because of the VOCs leaching into the water. If memory serves, it was an argument for the use of Drylok paint to seal your tank. Epoxy sounds like the best way to go, but also seems the most difficult.

[der_wille_zur_macht]

My concern with epoxy is more than just cost. I've never worked with fiberglass before, but I don't imagine its easy. I've never used epoxy, but from what i read it can dilute into the tank. Also, doesn't epoxy have to be mixed together to work? I just figured since i have the acrylic, I might as well use it. If you use 3/4" plywood, do you have biscuit join it or just screw it? What is euro bracing? Thanks for all the help. :)

Lining a tank with epoxy is easier than tying your shoes. You use dosing pumps to ensure you get the right ratio of the two parts, mix them, then literally just dump it into the tank. Repeat several times on each panel and you're done. It's 100% inert when cured, extremely durable, totally watertight, and will last longer than your interest in the hobby. It's very forgiving and hard to mess up, unlike working with acrylic. Trust me on this - if you're coming in to this with no direct experience in tank building, it'll be much simpler to line the wood tank with epoxy than acrylic.

I screwed and biscuited my tank, but the biscuits are definitely not strictly required. The first handful of pages in my build thread give a good step by step view of the techniques I used:

http://reefcentral.com/forums/showthread.php?t=1749114

[Psychotrshman]

Never built a tank before, so I'm looking for the hardest thing to mess up. :) What is a dosing pump? How do you attach glass to an epoxy tank?

[der_wille_zur_macht]

Look at the uscomposites site and find the epoxy page - dosing pumps are just dispensers you put in the top of the jugs of resin and hardener:

http://uscomposites.com/Images/epox/P11.jpg

Each push gives you a pre-determined amount of liquid, so you can't mess up the ratios - you just count pushes to get the right ratio for the hardener you're using. So, for instance, if you use their slow hardener, which needs to be mixed at 2:1, you just count out 2:1 pushes of resin:hardener.

Glass is attached to an epoxy'd tank with silicone. Typically you build a frame as part of the viewing panel, then silicone the glass panel to the inside of the frame. This way, the silicone is really acting as a sealing gasket, as the weight of the water will be compressing it against the wood frame and as such bond strength isn't totally critical (though given the size of the contact area, it will typically be very high anyways).

You asked earlier about bulkheads - that's also straightforward. You use a hole saw to cut a hole, then you just apply epoxy to seal the exposed wood.

The only real "hard" thing about this method is that it can take a long time. If you're looking at an 8 hour set time with the epoxy, and 3 - 4 coats per panel, you're basically going to need a few weeks to actually seal the entire tank. It's not a lot of actual work time, the difficult thing is that it's spread out over days/weeks as you need to wait for one pour to cure partially or fully before moving on.

[Psychotrshman]

I'm feeling better and better about epoxy. Waiting is easy, I don't have constant time to work on it, but a few hours once a week works nicely. I appreciate all the information. What are your thoughts on sealing the wood first, then once assembled, pouring epoxy in the joints? Or silicone the joints? If the epoxy just gets painted on, where does the fiberglass come in?

[der_wille_zur_macht]

Sealing the plywood first sounds like more work, since you've effectively got to do two sealing operations. Sealing once built ensures you have a continuous seal for the entire inside of the tank.

Not all people use fiberglass - it's simply a method for adding strength, but a 3/4" plywood box with a typical top brace, typical thickness of epoxy lining, and good assembly technique doesn't need extra strength.

To be clear, the epoxy is not painted on - you mix a large batch and just pour it on the panel of the tank you're working on. The implication is that you turn the tank such that whichever panel you're working on is down. Then when you pour the epoxy in, you spread it out across the panel with a spatula, and it self-levels on the panel. Typically you'd do several such "pours" on each panel of the tank, which ensures that if there's a pinhole leak in any given pour it gets sealed by successive layers.

[der_wille_zur_macht]

I should note that what I am describing is simply my own process based on how I built my own tank. While it's probably fair to say that I used a "mainstream" approach for an epoxy lined wood tank, there are definitely a variety of effective ways to do this, so you should research the various wood tank build threads, ask questions, and figure out what you want to do for your own process.

[Psychotrshman]

What would a typical top brace be? And how do you epoxy the bottom of the top and the front? Won't the openings cause problems?

[Psychotrshman]

Would plastic drywall mesh function like the fiberglass? Just for strength? How do you attach the overflow? Can you use acrylic for this or would you recommend epoxy coated wood? How would you epoxy the overflows inside surfaces? How do you keep the epoxy from coming out the tank openings when doing the front and the top? How do you treat the exterior of the tank? I know I'm full of questions, but this is sounding more and more do-able. :)

[der_wille_zur_macht]

Look at some build threads to get ideas of typical top bracing. Many people use a eurobrace style, which basically means you have a rim around the entire perimeter and no braces across the opening. I used a dual layer of 3/4" ply, 4" wide, as a eurobrace for my tank, for instance.

When you're pouring panels that have openings, you just "dam" the opening to prevent the epoxy from running out. Different people have used different techniques for this with varying degrees of success, i.e. masking tape or packing tape, plumber's putty, actual dams made from wood or foam, etc.

[der_wille_zur_macht]

Would plastic drywall mesh function like the fiberglass? Just for strength? How do you attach the overflow? Can you use acrylic for this or would you recommend epoxy coated wood? How would you epoxy the overflows inside surfaces? How do you keep the epoxy from coming out the tank openings when doing the front and the top? How do you treat the exterior of the tank? I know I'm full of questions, but this is sounding more and more do-able. :)

Plastic drywall mesh would be a poor choice as a reinforcement, compared to fiberglass - but again, the need for reinforcement is dependent on your specific design, so don't assume you need it.

Overflows can be attached in a variety of manners - it depends on the style of overflow. Some people build the overflow right in to the tank, out of plywood, and epoxy it the same as the rest of the tank. I built an acrylic box and siliconed it in to the tank.

Some people epoxy the outside of the tank, but it's not exactly standard or common. I epoxied the surfaces that would be most exposed - the top of the eurobrace, for instance, and painted the rest of the outside of the tank with high quality exterior house paint.

[Psychotrshman]

How do I calculate the amount of epoxy I need?

[Mr.Biggs]

This might help.

wood tank (http://reefcentral.com/forums/showthread.php?t=1436688)

There are many others and different ways to do them search for "wood tank".

[der_wille_zur_macht]

How do I calculate the amount of epoxy I need?

It's just a simple problem of finding the "volume" of the space occupied by the epoxy.

Let's say you were making a 10" cube, no top, no viewing panel. You'd have 5 panels, each 100 square inches, so 500 square inches of surface to cover. If you want 1/4" thick layer, you would need 125 cubic inches of epoxy. Convert to gallons, and it's .54 gallons. Obviously the math for a "real" tank is more complicated, but the process is the same - you just find the surface area you want to cover, multiply it by the thickness to get the volume, and convert to gallons.

[Psychotrshman]

Is there a typical thickness?

[der_wille_zur_macht]

Different people have different opinions. Typically it's between 1/8" and 1/4". Most people who do the "pour" method will do three or four pours on each panel - once you know the surface area of each panel, you can do math to determine the thickness for that panel, then divide by your number of pours to determine how much epoxy to make for each layer.

[whipsaw]

looks like you've got plenty of epoxy experts ITT, so just a thought from my own experience-

3 years back I was planning a slightly larger box tank, I compared costs on plywood/epoxy/glass and straight glass. I figured I'd need 4 sheets of 3/4" marine grade ply, ~5gallons of 2 part epoxy, one sheet of 1/2" front glass, and misc. lumber and fasteners which I have on hand. Checked prices through my local lumber store, glass shop and Aircraft Spruce for the epoxy. I came up with a figure of about $850 for materials delivered.

my local glass shop cut and delivered the glass for an all-glass box (5'x5'x32") for $997.

I know prices have gone up, and prices vary from place to place, but I wonder if the savings are really worth it if you're building a display tank and it's not going to look the way you want it. I really like the glass box I have sitting in the middle of my home office. To me it was easily worth the extra ~$47 I spent on it.