[Wanze]

I am hoping to get some help with my current DIY project. I am not construction a fish tank, but my project does need to be water tight, so I figured you guys might be able to help. I read on your forums about several plywood fish tanks, and the idea behind those designs is very similiar to my present need.

So, I am building something new this spring. We went to Erie PA with my son recently and he had a blast playing with something that I refer to as a water table. The thing was made by Tom Egan and can be found at this web site to give you an idea of what I am contruction.

http://www.tomegan.net/

Anyway, I did up some plans, and have attached to this email a picture of the table. Here is the issue, I need to make this thing waterproof. Its constructed of 3/8 plywood. In the picture, you can see that ther is a top level (which I made transparent), and this is where the water runs. When it gets to the bottom of the table, it falls through a drain into the bottom level which is where it collects to recirculate back up to the top holding area. I need to make all the plywood waterproof and have come up with serval options including Marine Epoxy Resin (with or without Fiberglass cloth), Marine Epoxy Pain, Liquid Neoprene, Sani-Tred. All of solutions are not cheep though, and with each additional coat of material, the cost goes up a lot. I'm not sure how many coats I would need and which if the products I can get away with.

The pit at the bottow where the water is stored and then recirculated back up measures 1'6" x 2'8" x 10" deep. The joints in this "pit" will have to hold the greatest about of pressure. Any thoughts?

Thanks so much!

 

[kingdave]

Many D.I.Y. tanks are constructed of a 2x4 or 2x6 frame with plywood walls. A layer of "Hardie Panel" fiber cement board is then put over the plywood and then sealed with multiple coats of Drylok basement waterproofer. The seams are then sealed with silicone. All of the materials are available at your local big box home center and at a far more reasonable price than the other alternatives you mentioned.

Try doing a search for "Drylok" on this forum and I'm sure you can find a thread that details a build such as the one I have mentioned.

 

[Wanze]

I looked at dryloc, but it dries "rough" which could be an issue when used in this application. I suppose I could use dryloc on all but the top main board (the one that's transparent in the picture). That board will have 1 3/4" pegs mounted on the top in a grid pattern. If the whole board was covered in dryloc, it would be really hard to afix the pegs perpendicular to the board.

 

[kingdave]

I looked at dryloc, but it dries "rough" which could be an issue when used in this application. I suppose I could use dryloc on all but the top main board (the one that's transparent in the picture). That board will have 1 3/4" pegs mounted on the top in a grid pattern. If the whole board was covered in dryloc, it would be really hard to afix the pegs perpendicular to the board.

What about laying in a plexiglass panel (with the pegs mounted on it) over the main board and letting gravity hold it in place? That way, the pegs could be mounted without making holes in the waterproof board and the plexiglass would provide the smooth surface that you require.

 

[Wanze]

Actually, that's a great idea. I was really trying to get around needing to buy a BIG sheet of acrylic, but I think that in the end, coughing up $25 for a shett of acrylic is going to be cheaper than doing the whole thing in an expensive resin.

If I recall my materials corrently, acrylic can be glues to acrylic with a glue like plumers use for PVC.

Actually, I re-ready your past and realized that you refer to this hardy board stuff. I thought the Dryloc was placed right on the plywood???

 

[kingdave]

In the tank builds I've seen on this site (which were for LARGE tanks) the Hardie Panels were used to add rigidity. I also am under the impression that the Drylok is meant to adhere to masonry rather than wood. Hardie Panels are a fiber-cement material.

By the way. I think the whole concept is neat. My son is a bit too small right now, but eventually I think it would be neat to see him play with this kind of setup. I remember creating streams and dams, etc. in the mud in the back yard when it rained and floating little "boats" through them when I was a child

 

[Wanze]

So I started construction today. I got all of the wood frame done and put in most of the plywood. This is where the questions begin. I noticed that in spite of meticulous measuring, there are a few places where the plywood edges meet where I can see a tiny crack of light coming through. The largest gap can't be more than 1/16 of an inch (probably less) but the edges are not as tight as I would have liked. I can try and recut the pieces and see if I can get them closer, but I think I will just end up driving myself crazy. If I use West System to seal the tank, with glass cloth along all the seems, will that be enough to "seal" that small gap? Should I seal it now, and if so, with what, before I epoxy and glass cloth the tank? Thanks.

 

[Mcdaphnia]

So I started construction today. I got all of the wood frame done and put in most of the plywood. This is where the questions begin. I noticed that in spite of meticulous measuring, there are a few places where the plywood edges meet where I can see a tiny crack of light coming through. The largest gap can't be more than 1/16 of an inch (probably less) but the edges are not as tight as I would have liked. I can try and recut the pieces and see if I can get them closer, but I think I will just end up driving myself crazy. If I use West System to seal the tank, with glass cloth along all the seems, will that be enough to "seal" that small gap? Should I seal it now, and if so, with what, before I epoxy and glass cloth the tank? Thanks.

You can seal the gap with dock adhesive, sort of a special kind of liquid nails. run a bead inside and force it through, leaving a small amount beveled inside the container. Bondo or wood fillers also work. Because of the emptying and activity around this use, two part epoxy is one of the likeliest waterproofing agent to hold up well. Pond and swimming pool products would be the others. Such as this brand: http://www.sanitred.com/waterproofing-b ... dfountain/ Drylok and fiberglass are too sensitive to flexing and wear.

 

[kingdave]

I would think that wood filler would be fine to fill those gaps since the West Systems product will be the waterproof barrier in the long run.

 

[Wanze]

Thanks so much everyone. An engineer friend of mine, who builds boats for a living, recommended a product called 3M 5200. Its essentially a super sealer that is waterproof both above and below the water line. Its likely overkill, but West System's epoxy bonds well to it, which makes it perfect for this application.

I had the unfortunate realization today that my project is 36" tall (its width is ~39"). My front door is only 35 3/4 inches. My patio sliding glass door apparently does not come out (the slider does, but not the stationary pane). Therefore, I had to so some modifications right when I saw just about done fabrication!!! ARGH!!! I essentially had to cut the bottom 5 inches off the whole thing. Luckily, I saw able to use a wood guide and a circular saw to get all that straightened out. I saw really afraid of cuting the things, as my experience with a circular saw is very limited, but I took my time, measured 18 times, and cut once. The cut was **** near perfect considering I had to cut all the way around the thing, staying at exactly the same height to keep it level.

Things are always harder than they appear.