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Discussion Starter · #1 · (Edited)
After months of researching, planning, designing and redesigning I'm finally ready to start this project. I initially planned to go with a custom built acrylic paludarium, but after seeking out some quotes I decided that the price was higher than I was comfortable with. So instead I've decided to do a DIY plywood/glass tank, and in the process ended up scaling up the dimensions a bit.

The dimensions of the tank are going to be 60.5"L X 28"W X 41.5" tall (~300gal). Water depth will be around 15", so overall water volume will be about 100gal.

The tank will be viewable from the front and right side. The casing is going to built from 3/4" birch plywood and the interior will be waterproofed with Pond Armor. The right side window is going to be a single piece of 3/8" glass. The bottom part of the front is going to have a 15" tall piece 1/2" glass and is going to have a braceless top edge. I'm going to add sliding door track onto the top edge of the bottom piece and have 2 pieces of 1/8" glass as sliding doors so that the upper part of the tank will be accessible from the front.

I"m going to install a skimless overflow system that will maintain a constant water depth and filtration will be a 40gal sump under the paludarium. The sump will return water through a manifold that will divide the flow between spraybars at the bottom and surface of the water section, and along the top of the back and left side feeding a clay dripwall for the upper portion. I'm going to be carving styrofoam branches that will be partly submerged and partly emersed and planted with epiphytes. I haven't decided whether I'm going to have any true land area, besides small pockets of substrate nestled into the clefts between branches, so the viv will be planted primarily with epiphytes.

I'll update as progress is made.
 

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Discussion Starter · #6 ·
Thanks for the encouraging replies guys.

I managed to get a good start over the weekend. Got all the plywood sheets cut and have started working on the stand. I managed to get all the pieces I needed from 4 (4'X8') sheets of 3/4" birch ply and 1 sheet of 1/2" ply (for the floor of the stand and some additional support pieces). All the vertical joints are mitered which will hopefully give me a clean, seamless look when it's done. I didn't have the tools to make the mitered cuts and cutouts in the panels myself, so I got some help from a guy I found through craiglist who did a great job on the cuts. If anyone in the Triangle area is looking for some help getting some wood cut up let me know and I'll pass along his info.

In addition to the plywood, I was initially going to use 2X4s as an interior support frame for the stand, but didn't like the quality of the wood I found at HD/Lowes (too warped). So instead I'm doubling up 1X4 strips of pine and plywood into multiple overlapping lap joints. This is giving me strong square joints.

Here's a pic of the approximate cutting plan I used to get the pieces I needed:
 

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Discussion Starter · #7 ·
what kind of clay will you be using for the drip wall?
I was planning on using sodium bentonite/kitty litter mixed with some organic material like peat moss, coco fiber and tree fern panel. I'm a long ways away from that stage and will probably be soliciting advice from the pros on here when I get there.
 

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Discussion Starter · #10 ·
Sorry for not updating. Progress has been a little slow. I'm almost done with the stand. I'll try to get some pics up when I get home from work. I ran into a few problems that complicated things a bit and have neccessited some sub-optimal fixes. Here's a few things I've learnt that would probably have already been obvious to a more experienced carpenter.

Were I to do this again I would NOT use miter joints on long structural joints. It's just too tricky to get everything to fit together perfectly and look good. I think a better method that would have given me a similar look and stronger joints would have been to just use butt joints on the plywood pieces and then covered them up with miter-edged trim pieces.

Don't assume that wood is the thickness that it's listed as. It turns out that my 3/4" plywood from Home Depot wasn't quite 3/4". It was more like 11/16". Unfortunately, when I made my calculations I figured that the inside edge of a mitered piece would be 3/4" less than the outside edge. Due to this oversight, the inside edge of a piece with two mitered corners is actually about 1/8" larger than I anticipated which means that my joints don't fit together as well as I hoped. I had to make some modifications to my initial design to work around this.

Epoxy glue cures very quickly. Most of my joints are glued with either Gorilla glue or Titebond III, but in the case of those poorly fitting joints with a 1/8" gap I decided to use epoxy for it's gap filling ability. Unfortunately, I made the mistake of thinking that epoxy glue would behave like epoxy resin (which it doesn't). I applied a heavy layer of the glue to both surfaces, assuming that excess glue would be squeezed out when I clamped the joint leaving me with a nice tight joint. Instead, by the time I'd applied the glue to all the surfaces and pressed them together the glue had already hardened enough that it didn't compress or squeeze out at all and instead left me with an even bigger gap! There's enough epoxy contact that I'm sure the joint is plenty strong but is cosmetically flawed and not quite flush with the other pieces.

Hopefully my mistakes will help out others working on similar projects.
 

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Discussion Starter · #12 ·
Ok, time for some long overdue updates to this thread. Progress has been very slow and I wanted to have something to show before updating.

It all started out with a pile of wood and inadequate workspace (thanks to my wife for tolerating the mess!)



Here's the start of the stand. I added some 1X4 pieces as additional support to the sides. The plywood casing itself serves as a structural component.



One of the top/bottom pieces of the front showing the 1/8" misfit due to the plywood not being quite 3/4" thick (see my previous post).



One of the legs - 1X4s doubled up with similarly dimensioned plywood strips



Skip ahead a few steps and the thing is mostly assembled



Closeup of how the sides fit together with the front/back. In addition to the glue the pieces are held together with pocket hole screws



Crappy looking gap due to my mistake with the epoxy glue hardening too quickly (again, see previous post).



I ended up using a syringe to fill the gap with West System 105/206 epoxy and then covering over that with wood filler. This means the entire gap is bridged by epoxy which should hopefully leave me with a strong joint and I don't think it looks too bad.



I stained the outside of the stand with a coat of "golden pecan" and finished it with 3 coats of satin polyurethane. The inside got 2 coats of Kilz followed by 2 coats of white latex paint.



Here it is with the doors balanced in place (still need to add some edge banding and mount the hinges). I'm going for a sleek ADA style look.

 

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Discussion Starter · #14 · (Edited)
Ok, here the progress with the tank itself.

As I mentioned earlier, I do not recommend using a mitered corner design like this. The joint lacks structural strength and it's very hard to get everything to line up. That being said, I decided to make the best of what I had and modified the edges to create sort of a haunched miter. This would offer a better supported joint with a much larger gluing surface. Here's the plan for how I hoped the edges would fit together.



I began by epoxying and screwing some 3/4" strips of plywood to the edges of all the pieces. When I first started out I was using just regular West System 105/206 (one coat to saturate the wood and a second coat for excess glue). As the build progressed I started to thicken the second coat with Cabosil and I highly recommend doing this. The thickened epoxy doesn't squeeze out as much and lets you load the joint with more glue.



Next I applied a coating of epoxy to all the joints (first a regular coat to saturate the wood, followed by a second layer of epoxy thickened with Cabosil) and screwed them together with 1.25" and 2" wood screws as shown in the diagram above.



Here's a closeup of the joints to show how they fit together. There's a screw every 2" but they're spaced in an alternating pattern. I used clamps to hold the sides together while driving in the screws. As expected, the mitered part of the joints didn't fit together quite as perfectly as I'd hoped leaving a bit of a gap on the back edges where I couldn't produce much clamping pressure. I solved this by injecting epoxy resin into all the gaps to produce a solid, epoxy-filled joint.



For bracing around the top edge I installed some strips of 3/4" plywood. The back and left side are just 3". The front and right side are 4" wide and I used a coping saw to make cutouts for future fan access.



I attached the strips with Titebond III and pocket hole screws. This is really strong - I did a set of dips supporting myself just on the bracing and it didn't budge (though I admittedly don't weight very much)! Eventually I'm going to add an additional 3" center brace running from front to back.



Here's the tank flipped over and the bottom bracing installed. Here I used 1X3 poplar strips, epoxied and pocket hole screwed like the top. The difference here is that the strips were attached 3/4" away from the edge, so that once the 3/4" plywood bottom panel is installed it will be flush with the bottom edge of the sides. You can see the bottom panel leaning against the wall in the background, pocket holes drilled and ready to be installed.



Here's the bottom installed



The bottom is glued to the sides and to the lower bracing with thickened epoxy. It is also screwed into the bottom bracing with screws every 2" and also screwed to the sides with pocket holes (staggered relative to the pocket holes in the bottom bracing).

You might recall I mentioned near the start how I discovered that "3/4" ply isn't actually 3/4" (more like 11/16"). Because the sides are joined with miters and my bottom piece is inset into the sides, this meant that the bottom was 1/8" too small. To deal with this I cut some 1/8" slivers from some scrap poplar and epoxied them into the gap. The pocket holes are actually driven through some of these poplar shims. I think this has addressed the problem quite well.



I filled all remaining screw holes and gaps in the bottom with wood putty, sanded and them painted with 3 coats of Drylok. Here's how it looks:



For those of you know don't know, Drylok isn't smooth like paint. It's filled with bits of sand. This means the resulting finish is quite rough and can't really be sanded for a smooth finish. Here's a closeup:

 

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Nice build. I'm anxious to see the outcome.

If I might add that a simple 2x2 frame the exact size of the interior, screwed from the inside, would have tightened that bad boy up some.

You got it covered though...just tossing out thoughts.

Keep the pics coming!

Edit: Oh Shit! My fault I didnt see this last post, looks like what you did to some extent...
 

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Discussion Starter · #18 ·
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