Solid wood vs plywood.

[Fishess]

Let's say i wanna build open frame stand for my aquarium.
I have option of using the following for each corner leg. Which leg would be better/stronger? (Tank size is ~35 gallon tall.)

2x4" solid pine log/planks.
VS
1.5x5" plywood strips at corners connected with screws/bracket, making "L" shape leg. (4 sheets having middle cut out like "window", then screwed together like a box.)

Leg length would be ~40"

I think simple 2x4" would be stronger?

 

[KrisReef]

Let's say i wanna build open frame stand for my aquarium.
I have option of using the following for each corner leg. Which leg would be better/stronger? (Tank size is ~35 gallon tall.)

2x4" solid pine log/planks.
VS
1.5x5" plywood strips at corners connected with screws/bracket, making "L" shape leg. (4 sheets having middle cut out like "window", then screwed together like a box.)

Leg length would be ~40"

I think simple 2x4" would be stronger?

I agree that natural wood is going to be more durable than laminate, although I think that laminate is stronger than wood before it encounters moisture over time?

 

[malacoda]

If you're making a box out of plywood sheets, and use both glue and pocket screws to join them, then you don't need the 'legs'. The plywood is plenty strong. And it leaves more room inside the cabinet.

The plywood stand I made for my 20g:

The plywood stand that is currently holding my 120g:

The plywood box is sitting on 4" x 4" blocks that are 4" tall.

The 'legs' on it ... and all the other trim pieces ... are simply 1/4" thick oak boards from HD glued to the front of the plywood to make it look pretty.

And the 1" thick 'framing boards' on the inside were merely to help align the panels and give a little more meat to screw into.

 

[malacoda]

I agree that natural wood is going to be more durable than laminate, although I think that laminate is stronger than wood before it encounters moisture over time?

The plywood will be plenty strong ... even stronger than 2 x 4 in the vertical direction. Dimensional lumber is less stable: more prone to shrinking/expanding/twisting with seasons/age. And both will deteriorate from contact with water if a finish isn't applied.

With a finish, either will work, but plywood will leave more space inside the cabinet for equipment.

2x4s can be a little easier to work with. They are also overkill ... by a mile ... for a 35g.

Most people tend to reach for 2x4s because they're more familiar ... and they don't fully understand or appreciate the strength and stability of plywood when it is used properly.

Think of it this way — brands like Red Sea, Waterbox, etc. don't even use plywood. They essentially use MDF-type composites that are painted with a durable finish and held together with put-together-furniture connectors (cams and screws). Plywood is stronger than MDF-type composite by a mile.

 

[Fishess]

It's not a CABINNET... I need sides to be open much as possible. (Pass-through.)
Also would prefer front somewhat open. More or less a TABLE type of stand.

Let's compare it more easily. 2x4" simple wood planks, or 2x4" plywood. Which would be stronger then? If i'm using plywood. I will be cutting middle out of the wall. Leaving behind only the 2x4" LEGS.

4 plywood sheets/walls having a big windows cut out in middle. Then glued/screwed together in box shape. All 4 sides will have BIG window in middle. Legs will be around 5" wide after cutting the windows.

 

[YOYOYOReefer]

My Stand uses 2 layers of 3/inch. footprint is 28 x96
its wide upon. The legs are 5 or 6 inch birch plywood strips doubled up in each corner like vertical L bracket. Legs and top ade all doble thickness plywood. I have a center brace in the back and have one for the front but it’s easily removable. Love having the big opening

my 300 gallons are on same stands but used 3 layers of 3/4 inch birch

 

[RocketEngineer]

1) Wood and plywood are both anisotropic materials which means “strength” is directional.
2) You have not defined what you mean by “stronger” so there is no means of evaluating it.
3) Based on dimensions, you’re comparing a 1.5X3.5 inch rectangle vs a 1.5X5 inch rectangle therefore giving one a significant dimensional advantage even before material strength is factored in.
4) There are more factors involved that are not being considered such as column stability/buckling, dimensional stability, and water resistance. Some of these can be mitigated with other methods but they should be factors in making a decision.

To answer the question: Because plywood is weakest in cross-plane compression while lumber is strongest in grain parallel compression, in a true strength test of these two, the 2X4 would have higher compression strength at failure.

As a side note: four 2X4s are enough to support thousands of pounds. That stand isn’t even close to needing that much support.

 

[Fishess]

1) Wood and plywood are both anisotropic materials which means “strength” is directional.
2) You have not defined what you mean by “stronger” so there is no means of evaluating it.
3) Based on dimensions, you’re comparing a 1.5X3.5 inch rectangle vs a 1.5X5 inch rectangle therefore giving one a significant dimensional advantage even before material strength is factored in.
4) There are more factors involved that are not being considered such as column stability/buckling, dimensional stability, and water resistance. Some of these can be mitigated with other methods but they should be factors in making a decision.

To answer the question: Because plywood is weakest in cross-plane compression while lumber is strongest in grain parallel compression, in a true strength test of these two, the 2X4 would have higher compression strength at failure.

As a side note: four 2X4s are enough to support thousands of pounds. That stand isn’t even close to needing that much support.

Do plywood actually have direction??? They are glued together by many smaller sheets. One that way another that way..
And those big long planks made out of wood - i don't see them be cut sideways... Tress aren't that wide.

By stronger i meant which would be better of.. What you mentioned - Stability, buckling etc... I thought most would know what i meant by stronger. (Hello this is fish/aquarium forum.)

No i was comparing 2x4" solid wood legs > to 1.5x5" plywood legs. Check my previous post - the stands that i plan to build will look like that. Dimensions: 28x20x44" (LxWxH) Box made out of plywood, with big windows cut in middle. (More or less 1.5x5" side strips..) Or 4 solid wood legs with frame on top of it. Bottom would be connected with big "L brackets to one 1.5" plywood sheet.

 

[RocketEngineer]

Plywood is typically produced by pealing the fibers off the outside of a tree trunk in a spiral to create a continuous sheet that’s as wide as the tree is long. Think how wrapping paper comes off the tube, that’s how the wood fibers are taken off the trunk segments. They then typically take multiple of these sheets and align the fibers at 90 degrees from one layer to the next. The result is a material that doesn’t change shape as much (because fibers are now running two directions instead of one) at the cost of strength along those fibers. Plywood doesn’t like being squished from the edges inward because only half the fibers are oriented in that direction (the others are the 90 degree ones. Because of this (and other factors) plywood is inferior in compression to the same thickness solid cut board.

 

[RocketEngineer]

Lumber no longer matches the short hand sizes and hasn’t for decades. If you purchase a “2X4” at any modern lumber store, the finish dimensions will be 1.5 inches by 3.5 inches. 2X6 is 5.5 instead of 6, a 2X8 is 7.25, and so on.

 

[RocketEngineer]

If you make the box out of 4 full panels with cutouts instead of cutting it into strips, plywood would be the better option because the corners would be one continuous piece vs having joints. Cutting the plywood into strips and reassembling it negates any of the benefits from using plywood. At that point, solid lumber would be the better option.

 

[jda]

If you cut up the ply into strips, then it will be weak - glue and hardware will not be as good as if you use a hardwood. I would avoid pine if you are going to build with 4/4 material - too soft for me... use a hardwood.

Go to the hardwood store and get some cheap hardwood which will be stronger at the glue and hardware joints. Making all 4 sides out of panels with the middle removed is good too, but most don't have tools to do this very well, but even a straight edge, circular saw and a hand saw can do this.

Hardware into ply is always like putting hardware into the end grain - just not great. End gluing ply does nothing for me.

 

[Enderg60]

my old 300 was on a plywood stand. It was just two layers of 3/4" with the joints reversed on one layer. Worked great for 12 years before I took it down.

Plywood is stronger when used correctly.

 

[cnseekatz]

Can I be the ****** who suggests square steel?