Question for a Structural Engineer regarding stand

[Tuffloud1]

I’m building a 260 gallon into my wall.

Tank dimension is 72 x 28

The back side of the 6 ft side will have no center bracing.

Which should I use for peace of mind?

2x6

Doubled up 2x6

Doubled up 2x6 with 1/2 plywood sandwiched in the middle

2x8

Also, for the legs on the 4 corners, will 2x4s doubled up work or do I need 2x6s doubled up?

 

[Flippers4pups]

This was taken from "Rocket engineer's" thread, credit to him:

"The basic principle of the design is two box frames connected by four legs. The upper one supports the tank and transfers the load to the legs. The legs are made of several pieces of 2X4 to assist in construction and sheething the stand in plywood for strength and cosmetics. The bottom frame transmits the load of the tank into the floor.


Design notes:
*The plan for this stand consists of 21 pieces. Like color pieces are the same length and of the same board size.
*The box frames are screwed together first, then the legs are built off the bottom frame, the top frame is then placed on top and secured to the legs.
*The green pieces are screw strips. These provide limited load strength but serve to make assembly easier and help keep the stand square.
*The blue piece between the upper rails (red) works to keep the upper rails from twisting.

Ok, now to the cut list:
First off: The calculations below are based off of a stand that is "W" inches wide X "D" inches front-to-back X "H" inches high.

(2) Red - Upper Rails: Length = W
These will be sized according to length: 2X4 for 48" or less for smaller tanks (Rule of thumb is 75g-90g); 2X6 up to 72" with 125g-150g being acceptable; For longer spans and larger tanks 2X8s are recommended.

(2) Yellow - Upper Ends: Length = D-3"
Theses will be made of the same material as the upper rails.

(4) Green - Screw Strips: Length = H-2"
These 2X4s are shorter then the tank is tall.

(8) Purple - Uprights: Length varies:
- 2X4 Upper Rails: Length = H -7"
- 2X6 Upper Rails: Length = H-9"
- 2X8 Upper Rails: Length = H-10.75"
These 2X4s support the weight of the tank. The ones on the short sides of the stand provide a flat surface for attaching a plywood facing and while they do provide some strength, they are optional.

(2) Orange - Bottom Rails: Length = W
These 2X4s act to spread the weight of the tank over a larger area.

(3) Blue - Bottom Ends: Length = D-3"

Covering the sides of the stand with plywood will help to stiffen the stand against twisting and shifting. Doors can be mounted to the legs as desired.

So there it is. 21 pieces in 6 lenghts equals a tank stand that should fit the bill for most people. There are other plans out there but this is a simple design using simple tools and common wood sizes. It may not suit everyone's application but it should fit the bill for most common size tanks."

 

[Tuffloud1]

This was taken from "Rocket engineer's" thread, credit to him:



"The basic principle of the design is two box frames connected by four legs. The upper one supports the tank and transfers the load to the legs. The legs are made of several pieces of 2X4 to assist in construction and sheething the stand in plywood for strength and cosmetics. The bottom frame transmits the load of the tank into the floor.


Design notes:
*The plan for this stand consists of 21 pieces. Like color pieces are the same length and of the same board size.
*The box frames are screwed together first, then the legs are built off the bottom frame, the top frame is then placed on top and secured to the legs.
*The green pieces are screw strips. These provide limited load strength but serve to make assembly easier and help keep the stand square.
*The blue piece between the upper rails (red) works to keep the upper rails from twisting.

Ok, now to the cut list:
First off: The calculations below are based off of a stand that is "W" inches wide X "D" inches front-to-back X "H" inches high.

(2) Red - Upper Rails: Length = W
These will be sized according to length: 2X4 for 48" or less for smaller tanks (Rule of thumb is 75g-90g); 2X6 up to 72" with 125g-150g being acceptable; For longer spans and larger tanks 2X8s are recommended.

(2) Yellow - Upper Ends: Length = D-3"
Theses will be made of the same material as the upper rails.

(4) Green - Screw Strips: Length = H-2"
These 2X4s are shorter then the tank is tall.

(8) Purple - Uprights: Length varies:
- 2X4 Upper Rails: Length = H -7"
- 2X6 Upper Rails: Length = H-9"
- 2X8 Upper Rails: Length = H-10.75"
These 2X4s support the weight of the tank. The ones on the short sides of the stand provide a flat surface for attaching a plywood facing and while they do provide some strength, they are optional.

(2) Orange - Bottom Rails: Length = W
These 2X4s act to spread the weight of the tank over a larger area.

(3) Blue - Bottom Ends: Length = D-3"

Covering the sides of the stand with plywood will help to stiffen the stand against twisting and shifting. Doors can be mounted to the legs as desired.

So there it is. 21 pieces in 6 lenghts equals a tank stand that should fit the bill for most people. There are other plans out there but this is a simple design using simple tools and common wood sizes. It may not suit everyone's application but it should fit the bill for most common size tanks."

“(Rule of thumb is 75g-90g); 2X6 up to 72" with 125g-150g being acceptable; For longer spans and larger tanks 2X8s are recommended.”

What if my span is 72” but I’m over the 125g-150g? I will be at 260g. Does this mean go 2x8 even though I’m not longer than 72” but heavier than 150g?

 

[Flippers4pups]

I would use the 2x8's.

 

[Tuffloud1]

I would use the 2x8's.

Thanks, that was my thought as well.

Do I really need kiln dried?

What are your thoughts on using a table saw to take off 1/4 inch to make sure the tops are totally straight? I heard someone do this but I’m trying to understand how you would accomplish this if the other side of the board isn’t perfect, since it would be running against the block/guide...,

Also, I’m assuming the crown should be up?

 

[Flippers4pups]

Thanks, that was my thought as well.

Do I really need kiln dried?

What are your thoughts on using a table saw to take off 1/4 inch to make sure the tops are totally straight? I heard someone do this but I’m trying to understand how you would accomplish this if the other side of the board isn’t perfect, since it would be running against the block/guide...,

Also, I’m assuming the crown should be up?

Kiln dried yes. No treated lumber! Don’t think it’s necessary to cut the tops off.

I would look for the straightest pieces possible. No crowns, just straight and flat. You’ll have to dig through the piles to find them.

 

[Tuffloud1]

Kiln dried yes. No treated lumber! Don’t think it’s necessary to cut the tops off.

I would look for the straightest pieces possible. No crowns, just straight and flat. You’ll have to dig through the piles to find them.

As far as “kiln dried”, is this considered “white wood” from Home Depot? Does Lowe’s or Depot have kiln dried?

 

[Flippers4pups]

As far as “kiln dried”, is this considered “white wood” from Home Depot? Does Lowe’s or Depot have kiln dried?

Most of their lumber is.

 

[dbjonesjr]

Make sure you don't cheap out on the lumber. Get nice and straight premium pieces (at least for the top) so you don't have to rebuild your stand when you find out your tank doesn't sit flush along the wood.

 

[SeaJay]

I’d get an engineered beam and sleep sound at night knowing it’s perfectly straight, strong enough and not going to sag. It’s dirt cheap insurance considering the overall cost of your build.

 

[dbjonesjr]

I’d get an engineered beam and sleep sound at night knowing it’s perfectly straight, strong enough and not going to sag.

Another great option.

 

[Flippers4pups]

I’d get an engineered beam and sleep sound at night knowing it’s perfectly straight, strong enough and not going to sag. It’s dirt cheap insurance considering the overall cost of your build.

If your going that far, steel stand is the best option.

 

[Tuffloud1]

Why would a regular 2x8 not be enough to where I wouldn’t sleep at night?

At 72 inches, it would have 1/16 of an inch or less deflection. Why would this be an issue as long as it’s reasonably straight?

 

[Flippers4pups]

Why would a regular 2x8 not be enough to where I wouldn’t sleep at night?

At 72 inches, it would have 1/16 of an inch or less deflection. Why would this be an issue as long as it’s reasonably straight?

2x8’s would be more than enough.

 

[Tuffloud1]

Why would a regular 2x8 not be enough to where I wouldn’t sleep at night?

At 72 inches, it would have 1/16 of an inch or less deflection. Why would this be an issue?

Most of their lumber is.

At Home Depot now, also went to Lowe’s. Only kiln dried they carry are 2x4s...

 

[Tuffloud1]

I was able to find top grade dry Doug Fir at Meek’s. Stuff is completely free of knots and perfectly straight. Ridiculously expensive at $8.45 a foot.

 

[SeaJay]

I was able to find top grade dry Doug Fir at Meek’s. Stuff is completely free of knots and perfectly straight. Ridiculously expensive at $8.45 a foot.

Looks like a nice piece of wood. I’d say that’s a rather reasonable price for what you’re getting. I think you’ll be happy with the result.

 

[Tuffloud1]

What size/type of plywood do you guys recommend for the top platform?

 

[Dkeller_nc]

Ideally, you'd want 7/8" Baltic Birch veneer-core plywood, but it may simply not be possible to obtain in a 4x8' sheet, which is what you'll need for a contiguous top. Baltic Birch is generally free of most defects such as knots, but it can be hard to source. Failing that, I'd strongly recommend getting veneer-core plywood - I'd be concerned that MDF core would creep under the weight of the tank.

By the way - you didn't mention whether this was a rimmed or rimless tank. I suspect rocket engineer's stand was designed for a rimmed tank; a rimless may require some cross-bracing in at least two places across the top to support the center of a rimless tank.

 

[Tuffloud1]

Ideally, you'd want 7/8" Baltic Birch veneer-core plywood, but it may simply not be possible to obtain in a 4x8' sheet, which is what you'll need for a contiguous top. Baltic Birch is generally free of most defects such as knots, but it can be hard to source. Failing that, I'd strongly recommend getting veneer-core plywood - I'd be concerned that MDF core would creep under the weight of the tank.

By the way - you didn't mention whether this was a rimmed or rimless tank. I suspect rocket engineer's stand was designed for a rimmed tank; a rimless may require some cross-bracing in at least two places across the top to support the center of a rimless tank.

It’s rimmed.