Compare Bending Resistance of Dimension Lumber used as Joist

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PAUL GRAHAM said:
One thing I would be inclined to do, but not shown here, would be to double the front panel thickness, as the cutout is very large. A second similar piece 47.5 inches wide could be laminated on for a 1.5 inch total thickness.
Cutouts should not have square corners, they should be rounded. Maybe use a hole-saw, 3" diameter or larger.

The large front cutout will release material that can be used in other places. For example, the inner lamination of the front could use several pieces, that straddle the corners.

Narrow strips of ply are not as strong as solid timber. The thin bottom strip may not be needed, or it might be replaced by a length of solid wood.
 
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Thanks Baluncore.

The thin bottom strip of the front panel overlays the edge of the 1.5 inch floor and is screwed and glued to solid timber. This brings the floor out flush to the face of the front panel.

The top edge of the front panel could be reinforced with a 2 x 4 lintel on the inside, with steel angles tying the ends to the front verticals. I will do this.

I can certainly make the cutout corners rounded as you suggest.
 
Thanks to all you guys for your input on my project. This started out one way and went somewhere else. It's a better solution than the original, so I'm grateful for your interest. When visitors come to admire my fish, I'll point out the aquarium stand designed by a committee of physicists.
 
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Has anyone ever seen an aquarium stand sag? Don't the glass panels of the aquarium form beams?
 
Herman Trivilino said:
Has anyone ever seen an aquarium stand sag? Don't the glass panels of the aquarium form beams?
I have seen the glass floor broken as a result of sag due to insufficient support.
The sides are beams, but the glass floor sags and presses against the supporting plate. That is why a foam layer is placed under the aquarium, to remove point contacts that might initiate failure. There is no vertical force component applied by water to the wall, just the weight of the wall glass.
 
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Baluncore said:
The sides are beams, but the glass floor sags and presses against the supporting plate. That is why a foam layer is placed under the aquarium, to remove point contacts that might initiate failure.

Good point. Never heard of the foam but it seems a good idea.

So the most support is needed not along the vertical edges but in the center?
 
Today's glass aquariums are built on two styles, rimmed, or framed, and rimless. A rimmed aquarium possesses a plastic one-piece molded frame at the top and bottom that fits around the perimeter of the glass and binds the perpendicular joints tightly. In larger sizes there are cross-braces, at least one mid-tank, that reinforce the stiffness of the frame and space the two parallel long sides to the specified dimension. Also after a certain tank size, the bottom pane is tempered. The glass thickness increases in large tanks because the walls will deflect. While the frames bind the assembly and hold the sealed edges immobile, the weight of the water will try to bend the large spans outward.

The plastic rims are beefy and there are material dimensions to consider. These are between 1/8 and 1/4 inch thickness and 1/2 to 1 inch width depending on tank size. A framed tank set on a level surface platform is elevated by that thickness. That is, the weight of the tank is transferred to the surface through the frame only, and the bottom pane of glass does not contact the surface. Thus the platform's supporting area must underlay the frame throughout its entire perimeter and it is irrelevant whether the platform has a contiguous surface. Commercially made aquarium stands for framed tanks typically do not have fully contiguous surface platforms but are totally open. In the case of a contiguous top, it is possible that a large tank's bottom glass could, by happenstance, contact the neoprene leveling mat, but this is not intended in the tank's structural design by necessity.

Therefore, the support is solely under the vertical edges and there is no support in the center. What is important is that the vertical edge support must be uniform throughout the perimeter as though the platform were a contiguous, perfectly level surface. If the platform is not level to all edges, the seals will be stressed, whether the top of the stand is open or contiguous.

I have only ever used framed tanks. A rimless tank does contact the platform surface fully because there is no bottom build-out elevating the tank, as it has no frame. Rimless tank construction is innovative technology. I don't have experience with these, but I would not trust them without a fully contiguous supporting surface.
 
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