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Discussion Starter #1
I've read everything from drylok, pond liner, to epoxy for sealing plywood vivs.

I'd like to know your tested and favorite procedures for sealing plywood vivs.

Example:

1) caulk all seems
2) coat with epoxy paint brand xyz
3) great stuff on top for shaping

Hopefully this will be a nice reference thread.
 

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I used pond armor and fiberglass for the seams. West system is also very popular. The seams is where most people run into trouble. I've not seen anyone successfully use drylock and keep it from leaking after a few years. I ran into trouble around a bulkhead with the epoxy not being flat enough to get a good seal. But that issue at least is fixable with enough careful sanding. Look into plywood aquariums for more tips.
 

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1) Build the tank with robust joints to begin with. You are basically building a cabinet. It's easier to look up examples of good cabinet joinery than trying to find how tos on plywood vivaria. I use pocket hole screw joints and glue. For aesthetics, keep the pocket holes on the interior of the tank and then fill them with dowels. Sand everything flush and fill any other small cracks or voids with a wood filler epoxy. Make sure the interior is clean and the surface is sanded/prepped to the standards that the epoxy brand you use calls for...

2) I use pond armor. There are other epoxy options but that's the only one that I've used successfully. I would absolutely go with an epoxy for this step. I have never used any fiberglass reinforcement for the joints. Fiberglass in the joints is done for fish tanks where the build will hold many hundreds or thousands of pounds of water, but I feel it's probably unnecessary for a vivarium that might have an inch or two of water in the bottom. But do what you think is best. Overbuilt is always better than underbuilt. 3/4" plywood is very strong and has very good dimensional stability for the tank sizes I have built. I haven't built any tanks larger than about 2.5 feet wide, 20 inches deep, 3 feet tall.

3) Silicone sticks to epoxy very well. Great stuff stick alright - probably about the same as to glass. When I'm going to use great stuff to cover the sides/background, I silicone a piece of egg crate to the epoxy first. This gives the great stuff far more surface area to cling to. I've never had any problems mounting heavy wood to the background using this method.

I'm not an expert by any means. I've built about 8 plywood tanks so far and change something every time based on what I learned from the previous build. Have fun with it. It can be a lot of work to do it right, but it will be something unique that you can be proud of. Here are a few my wife and I just finished up.

296878
 

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Discussion Starter #4
1) Build the tank with robust joints to begin with. You are basically building a cabinet. It's easier to look up examples of good cabinet joinery than trying to find how tos on plywood vivaria. I use pocket hole screw joints and glue. For aesthetics, keep the pocket holes on the interior of the tank and then fill them with dowels. Sand everything flush and fill any other small cracks or voids with a wood filler epoxy. Make sure the interior is clean and the surface is sanded/prepped to the standards that the epoxy brand you use calls for...

2) I use pond armor. There are other epoxy options but that's the only one that I've used successfully. I would absolutely go with an epoxy for this step. I have never used any fiberglass reinforcement for the joints. Fiberglass in the joints is done for fish tanks where the build will hold many hundreds or thousands of pounds of water, but I feel it's probably unnecessary for a vivarium that might have an inch or two of water in the bottom. But do what you think is best. Overbuilt is always better than underbuilt. 3/4" plywood is very strong and has very good dimensional stability for the tank sizes I have built. I haven't built any tanks larger than about 2.5 feet wide, 20 inches deep, 3 feet tall.

3) Silicone sticks to epoxy very well. Great stuff stick alright - probably about the same as to glass. When I'm going to use great stuff to cover the sides/background, I silicone a piece of egg crate to the epoxy first. This gives the great stuff far more surface area to cling to. I've never had any problems mounting heavy wood to the background using this method.

I'm not an expert by any means. I've built about 8 plywood tanks so far and change something every time based on what I learned from the previous build. Have fun with it. It can be a lot of work to do it right, but it will be something unique that you can be proud of. Here are a few my wife and I just finished up.

View attachment 296878
What wood filler epoxy do you use? Would caulk work?
 

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This is what I have used to fill small cracks and plywood voids, as well as small holes remaining after plugging pocket holes. One stick should be plenty for even a large tank. Some type of caulk might work? I would feel better about the cured product having a surface closer to that of wood for the sake of the epoxy. If in doubt just call the manufacturer of the epoxy you're using and ask. I've called Pond Shield and they are very willing to help with any questions you might have about using their product. Same for Polygem, though I personally didn't have as good of results with their epoxy.
 

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I've read everything from drylok, pond liner, to epoxy for sealing plywood vivs.

I'd like to know your tested and favorite procedures for sealing plywood vivs.

Example:

1) caulk all seems
2) coat with epoxy paint brand xyz
3) great stuff on top for shaping

Hopefully this will be a nice reference thread.
Caulking the seems is a very odd thing that got popular. Putting a hard material over a soft one is not a great method. The proper way to do it and increase the strength of the tank is epoxy fillets. You thicken the epoxy with a filler of your choice, talc powder is the cheapest but you can use a low density one like microballoons that will give a nice fillet and increase the strength of your build hugely. You want laminating epoxy and not the casting stuff. West coast is well known but you can get much cheaper stuff online as no name laminating epoxy.
using some fiberglass cloth is also good, from just tape on the edges or you can use a light cloth for all surfaces which adds a lot of strength and puncture resistance over just epoxy. Just be sure it is the correct cloth for epoxy and not the type with styrene for polyester which is not waterproof like epoxy.

When working with epoxy it is best to do the next layer before the epoxy has fully set, so you get chemical bonding instead of just mechanical. You can also coat screws in wax and set them in thickened epoxy for easy waterproof mounting points.



The best resource that is free is this book on boat construction https://www.westsystem.com/wp-content/uploads/GougeonBook-061205-1.pdf

plus the guide

and a general epoxy video
 

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This is what I have used to fill small cracks and plywood voids, as well as small holes remaining after plugging pocket holes. One stick should be plenty for even a large tank. Some type of caulk might work? I would feel better about the cured product having a surface closer to that of wood for the sake of the epoxy. If in doubt just call the manufacturer of the epoxy you're using and ask. I've called Pond Shield and they are very willing to help with any questions you might have about using their product. Same for Polygem, though I personally didn't have as good of results with their epoxy.
if you have just laminating epoxy you can mix in saw dust which can be bought as a filler or just whatever you have kicking about really. West Coast has a specific filleting filler that works well.
 

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I'm not an expert by any means. I've built about 8 plywood tanks so far and change something every time based on what I learned from the previous build. Have fun with it. It can be a lot of work to do it right, but it will be something unique that you can be proud of.
Likewise. I have a similar amount of experience making plywood vivs. And a very similar quality of experience: I keep learning and adapting, and like how I do it now (but still, I keep adapting and learning).

My current method looks something like this:
  • build hull (glue & screw), rough in any penetrations
  • drylok entire interior plus penetrations (mask exterior)
  • epoxy all interior bottom and vertical surfaces, except where any foam will go - leave those just dryloked (ceiling is also just drylok, not epoxied)
  • install vents & bulkheads
  • do any exterior finishing
  • carve any foam installs, epoxy and color on bench top (leaving attachment face bare)
  • install foam pieces onto drylok'd hull, using silicone
  • install doors
  • install lights and misters
 

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I have never built a plywood tank. But, I have worked in the construction business for over 20 years. I think the idea behind caulking the corners it to allow a small degree of movement between the two panels without a crack transferring through the epoxy. But, that is just a guess.
 

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I have never built a plywood tank. But, I have worked in the construction business for over 20 years. I think the idea behind caulking the corners it to allow a small degree of movement between the two panels without a crack transferring through the epoxy. But, that is just a guess.
I could see that if you glass the corners. But with the fillets of epoxy the joints will be very stable, it pretty well removes all the force concentrations from the corner and allow the long panels to take it up. I have not built a ply tank myself but I have done a lot of work on my wood boat and epoxy fiberglass, especially biaxial cloth is disgustingly strong. Plus being a composite you can do some interesting things like mix in something like graphite to make a sliding part or add some carbon fiber for crazy stiffness. That book I linked has a lot of great info on building with epoxy and as long as it is bog standard laminating epoxy it all acts pretty much the same. From the ebay random chinese stuff to marine grade. You can even post cure cheap epoxy and bring up its strength.
 

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I could see that if you glass the corners. But with the fillets of epoxy the joints will be very stable, it pretty well removes all the force concentrations from the corner and allow the long panels to take it up. I have not built a ply tank myself but I have done a lot of work on my wood boat and epoxy fiberglass, especially biaxial cloth is disgustingly strong. Plus being a composite you can do some interesting things like mix in something like graphite to make a sliding part or add some carbon fiber for crazy stiffness. That book I linked has a lot of great info on building with epoxy and as long as it is bog standard laminating epoxy it all acts pretty much the same. From the ebay random chinese stuff to marine grade. You can even post cure cheap epoxy and bring up its strength.
That's some interesting stuff. I will check out the link.
 

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I think the idea behind caulking the corners it to allow a small degree of movement between the two panels without a crack transferring through the epoxy. But, that is just a guess.
Hmm. I kind of doubt it for a couple reasons. You're right about cracks - most epoxies are very brittle. I've never worked with Pond Armor but I think it is a bit flexible. Many epoxies - like West 105 - are runny like water. I suspect the caulk may be just to keep the damn epoxy inside the raw hull.

I don't caulk with the 2 epoxies I've used. It's not like my carpentry is that great - it isn't. But I get pretty tight and stiff with the glue and screw. And I've only used two products in my builds (so far) - a putty (Polygem's 107 Lite) and a high-viscosity brushable (Smooth-on's Habitat Cast n Coat). Neither is inclined to just run away from you, down any little tiny crack or hole. I've heard the West 105 is kind of a bitch that way, it'll all drain out of just a pinhole, it's so stinkin runny. So Im told anyway, I've never used it.

Incidentally neither of the epoxies I have used accepts silicone adhesion worth a shit in their cured, raw state. Either one can do OK if it's been coated with a good dusting of dry pigment, or has been painted with acrylic craft paint. Both of those coloring methods need to happen while the epoxy is still tacky, not fully cured. That's (hopefully!) obvious with the dry tint, but it's also an issue with paint. At least in high-humidity situations that get shot pretty often with streams of water from a hand-sprayer. I might give the Pond Armor a try, if it really does accept silicone adhesive in its raw, uncoated state.

Anyway - some thoughts. Free, and perhaps no bargain at the price. Ha ha.
 

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Oh - on the fillets. Definitely on something like an aquarium! Or even a palu. But for a viv with maybe an inch of water in a false bottom - nah. I wouldn't bother. Just build a stiff hull so you don't crack your seal job when moving it around, and you're most likely fine. The fillets are to bomb-proof it under high weight and considerable pressure. I've never used them in my plywood vivs. Some of which are pretty old now, and have been moved around any number of times, including in a moving truck, as well as up and down stairs, and from shelf to shelf in the herp room. No leaks. But the hulls are stiff, glued and screwed.
 
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