Questions about plywood only stand

[schulzjp]

Hi,

 

I'm planning on getting back into the hobby with a 20H display with a 15 gallon sump. I really want to build the stand with plywood only without a 2x4 frame to limit the bulk of the stand. The reason for this is is the display tank and sump have the same footprint. Every stand I have built before had the edges of the tank line up exactly with the edge of the stand so that the weight will be distributed directly to the frame; however, in order to have a sump and display tank with the same footprint, I'm planning on having the tank rest on a 3/4"+ sheet of plywood which lies flat across the top. This means the tank will be smaller than the frame and not be applying its weight directly down onto the frame (if that makes sense). I'm assuming that can hold since many floors are 16" spacing and that handles some good weight, and I'm only planning on a 14" spacing front to back. My concern is of the plywood bowing and the tank falling through. I'm guessing I can cut some slots in the drywall so I can make something like 1x2 or 1x4 joists under the plywood top. Please let me know your thoughts.

[RubberFrog]

You'll be fine. 3/4" plywood will show zero deflection for the tank, even up to 3" from the edge.

[wvreef]

when you make the sides of the stand out of plywood, go and make a frame out of 2x4 for the top and screw them to the plywood and glue them as well, then put your plywood top on and no need to worry abour plywood bowing as the weight is now distrubted to the plywood sides hope this helps

[trockafella]

I have an iron stand that has a built in area for the same size tank underneath. I had wood cut and used magnets to attach the wood to the metal stand. The iron stands are relatively cheap and seem to be very sturdy. Its also nice bc I can pull off 3 sides.

[dave w]

The tank weight will be no problem. 20 gallons only weighs 160 pounds which is less than a person standing on the floor, and tanks are usually against a wall. 3/4" plywood will take at least several inches of cantilever without bowing. The most important thing about your stand is to cross brace it. You don't want someone giving the tank a good bump and seeing it collapse. Plywood on the back is perfect, so is a board or piece of plywood made to form an X or a K from one top corner to a bottom corner. The diagonal gives it the strength. Try to do this on the sides also, although solid plywood doesn't need this type of bracing. Hope that helps.