Plywood only stand for 180 Gallon

[alton]

You can't beat baltic plywood! The first two pictures are my new 310

And if you can afford it solid oak hardwood the last picture was my 300DD

 

[Eric R.]

My biggest one is the span. I plan on running without a center support, as I see many builds holding a 180 gallon like this with 2x6 headers.

My plan is to sister 3/4" plywood with glue to accomplish the same thing. From what I'm reading elsewhere, it should be plenty strong.

Is there a reason that you don't want a center support? I'd be pretty concerned spanning that distance with just a 2x6 with that much weight, though the same amount of plywood glued together should be as strong as dimensional lumber (so doubling up two pieces of 3/4" plywood with a construction adhesive). I'd still be concerned though. With wood, actual breaking often isn't as big of a deal as deflection. With aquariums, we want to avoid this, as it puts stress on the glass, and can cause the water to additionally put uneven stresses on the glass.

I'm not an engineer, just someone who took some engineering and drafting classes in college, is decent at math and science, and has some carpentry experience. I built an all plywood stand for my 55g which is rock solid, and has a doubled plywood "header"/face frame. It's hard to get span tables and such for plywood (that I've been able to find at any rate). It's also sometimes challenging to use a span table to look at the strength of dimensional lumber, and I'm personally unsure how to translate the live load/dead load calculations they are based on to an aquarium stand design.

 

[JoshH]

My biggest one is the span. I plan on running without a center support, as I see many builds holding a 180 gallon like this with 2x6 headers.

My plan is to sister 3/4" plywood with glue to accomplish the same thing. From what I'm reading elsewhere, it should be plenty strong.

If you're set on 3/4" I would triple it up personally, but ideally I'd do 2-3 layers of 1"BB as mentioned above if it's available to you. Being that its plywood you can also make the header whatever size you want. Your not stuck by the standard 2x6/8/10 sizes. Make the header as thick as you can without compromising your access into the stand. Even making it Actually 6" its already wider than machined lumber.

 

[Eric R.]

If you're set on 3/4" I would triple it up personally, but ideally I'd do 2-3 layers of 1"BB as mentioned above if it's available to you. Being that its plywood you can also make the header whatever size you want. Your not stuck by the standard 2x6/8/10 sizes. Make the header as thick as you can without compromising your access into the stand. Even making it Actually 6" its already wider than machined lumber.

I agree. I think 3 layers of 1"BB would be nice, especially it the header piece is actually 6" wide, and properly supported for the full thickness on each end. Also making sure that the weight of the plywood transfers directly to other plywood to the floor, and doesn't depend on fasteners which could fail.

 

[tmnails]

Is there a reason that you don't want a center support? I'd be pretty concerned spanning that distance with just a 2x6 with that much weight, though the same amount of plywood glued together should be as strong as dimensional lumber (so doubling up two pieces of 3/4" plywood with a construction adhesive). I'd still be concerned though. With wood, actual breaking often isn't as big of a deal as deflection. With aquariums, we want to avoid this, as it puts stress on the glass, and can cause the water to additionally put uneven stresses on the glass.

I'm not an engineer, just someone who took some engineering and drafting classes in college, is decent at math and science, and has some carpentry experience. I built an all plywood stand for my 55g which is rock solid, and has a doubled plywood "header"/face frame. It's hard to get span tables and such for plywood (that I've been able to find at any rate). It's also sometimes challenging to use a span table to look at the strength of dimensional lumber, and I'm personally unsure how to translate the live load/dead load calculations they are based on to an aquarium stand design.

Post #11 from the thread linked below is my reference. The picture sourced in his comment is years old, I remember the man who rendered it claimed he was actually a rocket engineer, and Im inclined to believe him lol.

show me your DIY plywood stands

Hey guys! soooo i am thinking about setting up yet another tank a 40br thinking about a DIY plywood stand i have a kreg jig and glue. just need a template and/or ideas so post pic of your build or link to a thread.

www.reef2reef.com

My general reason is accessibility. My sump will be located there, and if I can build the stand without the center brace and retain the integrity I need, I'm gonna do it.

 

[BZOFIQ]

Found these few years back, kept for inspiration, in the end went with Alu profile stand.

Agree with above posters on Baltic Birch - absolutely SOLID material.

 

[Eric R.]

Post #11 from the thread linked below is my reference. The picture sourced in his comment is years old, I remember the man who rendered it claimed he was actually a rocket engineer, and Im inclined to believe him lol.

Here's the thread I believe you are referring to: http://www.reefcentral.com/forums/showthread.php?threadid=1169964

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.

So he recommends larger for tanks larger than 150. 125s and 150s usually are less wide (18" compared to 24") and weigh 300-700 lbs less full.

I do tend to overbuild things, since I'm not actually an engineer and for peace of mind (for myself and for my other housemates )

 

[tmnails]

Here's the thread I believe you are referring to: http://www.reefcentral.com/forums/showthread.php?threadid=1169964




So he recommends larger for tanks larger than 150. 125s and 150s usually are less wide (18" compared to 24") and weigh 300-700 lbs less full.

I do tend to overbuild things, since I'm not actually an engineer and for peace of mind (for myself and for my other housemates )

That is TOTALLY the thread, I couldn't find it thank you.

Interesting he recommends 2x8, even just going from a 150 to a wider 180. That's enough to convince me... 2x8 plywood it is. I'll get pictures in here when I'm done. (Have to find time to build this thing first lol)

 

[Sleepydoc]

The rocket engineer design has been around for a long time. It’s fine, but is signficantly overbuilt and wastes a fair amount of space. The other issue is that straight dimensional lumber is difficult to find, so getting the top flat can be difficult.

If you want proof that plywood can be strong, look at LVL lumber. LVL beams are routinely used to span significant distances and hold significant amounts of weight. The problem with designing/engineering an aquarium stand is no one has the necessary numbers. As someone mentioned above, the numbers for plywood are hard to come by, but I‘ve never seen *any* numbers regarding how much deflection is allowable for an aquarium, so even if you do the calculations, you still don’t know if it’s adequate.

The original ’factory’ stand for my 120 was made from particle board with a few 1x3’s thrown in. Of course it had a center brace, but when I made my own stand (out of hickory) I noticed a gap under the center of the tank when I put it on the stand. Alarmed, I got the straight edge out only to find out tat the top of the stand was flat but the bottom of the tank wasn’t! After filling it up, that 1/4~1/2mm gap is still there, so I guess all the stressing I did over the strength of the crossbeam for the stand was for naught!

Regarding your stand, having enough room to work is important, but you’ve got a 6’ tank, so you could easily have a 2.5~3’ opening which gives quite a bit of room. Something else you could do is have 3 doors and have the center brace between two of them be a false one so you’d essentially have about a 3.5’ span on one side. That should give you plenty of room while still reducing the span signficantly.

 

[Eric R.]

If you want proof that plywood can be strong, look at LVL lumber. LVL beams are routinely used to span significant distances and hold significant amounts of weight.

Plywood is quite strong compared to dimensional, especially because so much of the common dimensional lumber you find at big box stores is NOT straight. However, there is an important difference between plywood and LVL in terms of strength - the grain in veneers in LVL is all parallel, while in plywood it changes directions.

Another consideration with plywood is voids. I don't believe they are common in true baltic birch plywood, but not uncommon in lower grade veneer ply, like regular birch plywood. The maple veneer ply I used for my stand for my 55g definitely had voids, but with only a 55 I wasn't too worried, especially since I doubled up the 3/4" ply.

tmnails, be sure to get true baltic birch, you'll probably need to go to a true lumber yard to get it in a large enough sheet. The 3/4" stuff should be 13-ply, not 5.

 

[reelss]

In the end I went with 2x4s and Plywood. The stand build is in the build thread here: https://www.reef2reef.com/threads/reelsss-180-gallon-build-diy-heavy-basement-sump.668523/

 

[Sleepydoc]

Plywood is quite strong compared to dimensional, especially because so much of the common dimensional lumber you find at big box stores is NOT straight. However, there is an important difference between plywood and LVL in terms of strength - the grain in veneers in LVL is all parallel, while in plywood it changes directions.

Another consideration with plywood is voids. I don't believe they are common in true baltic birch plywood, but not uncommon in lower grade veneer ply, like regular birch plywood. The maple veneer ply I used for my stand for my 55g definitely had voids, but with only a 55 I wasn't too worried, especially since I doubled up the 3/4" ply.

tmnails, be sure to get true baltic birch, you'll probably need to go to a true lumber yard to get it in a large enough sheet. The 3/4" stuff should be 13-ply, not 5.

Yes - there are definitely differences between LVL and plywood, and not all plywood is the same, either. I probably should have be more clear in my other post. I was just trying to make the point that ‘regular’ lumber is not necessarily stronger.

When you go to buy plywood, prepare for a shock. Good baltic birch plywood is not cheap - like anything, you get what you pay for.

 

[Eric R.]

Yes - there are definitely differences between LVL and plywood, and not all plywood is the same, either. I probably should have be more clear in my other post. I was just trying to make the point that ‘regular’ lumber is not necessarily stronger.

When you go to buy plywood, prepare for a shock. Good baltic birch plywood is not cheap - like anything, you get what you pay for.

It's hard to know how much someone on a forum you've never met knows! When it comes to structural things, I'm cautious, with building or sharing info. You probably know more than I do about this at any rate! If I'm sharing things that everyone in this thread already knows, sorry! Hopefully it's helpful for those rare few that do know how to use a search function on a forum and may see this thread in the future. I know I did a lot of searching before building my first plywood stand, and I already had some experience building cabinets. I think plywood stands are great, and would love to see more people give them a try, as long as they are well designed and built.

 

[Eric R.]

Here are pics of the stand I built for a 55g. Still needs doors, a sanding, and a good finish, just being test fit here. All 3/4" maple veneer ply.

 

[BZOFIQ]

All these stands are far overbuilt - you can sleep easy. Looks at what Aqueon sells for their 125-180 tanks, heck look at the IKEA like particle board stands all modern, rimless manufacturers ship with their tanks.

 

[BZOFIQ]

Yes - there are definitely differences between LVL and plywood, and not all plywood is the same, either. I probably should have be more clear in my other post. I was just trying to make the point that ‘regular’ lumber is not necessarily stronger.

When you go to buy plywood, prepare for a shock. Good baltic birch plywood is not cheap - like anything, you get what you pay for.

When shopping for this stuff at a decent place (no not home depot or lowes) you can also ask for EuroPly. No voids there because usually edges dont get sealed or finished. I have few boards in the garage of 3/4 and 1-inch variety, will snap a picture of their edge tomorrow.

 

[tmnails]

All these stands are far overbuilt - you can sleep easy. Looks at what Aqueon sells for their 125-180 tanks, heck look at the IKEA like particle board stands all modern, rimless manufacturers ship with their tanks.

This is it right here.

As sleepydoc said, no one has verified numbers on plywood, so we're all sort of going with what we feel is strong enough.

But one metric we DO have is manufacturer built tanks from the likes of aqueon and red sea. It's seems like a safe assumption that these companies engineered their stands. If we could somehow compile dimensions for these stands at a few different common tank sizes, that would put a lot of this to rest.

I would probably take whatever red sea or aqueon uses as a minimum, make mine a touch beefier, and sleep easy Good call BZOFIQ

 

[don_chuwish]

I find good baltic birch at a local place that recycles building materials. Lots of scraps from cabinet shops end up there - half or quarter sheets usually. It's what I used for my 25G Cube Reboot stand.
But to the question about unsupported spans - the key to a strong beam is DEPTH more than thickness. A 2x8 beam is stronger than two 2x4s sistered together. I forget who I'm quoting, but I've saved this for reference:
===
What you need to do to answer your question is to look at the term, I, which is the "Moment of Inertia" of the beam, and is dependent on the SHAPE of the beam.

For a solid rectangular beam, I = (b*h*h*h)/12
or, the width of the beam times the cube of it's height over 12.

So, all things being equal, the deflection of a 2X4 and a 2X6 under a given uniformly distributed load will be proportional to the calculated values for I for the 2X4 and the 2X6. And, since the width of the beams is going to be the same (1 1/2 inches) in both cases, the ratio of the beam deflections will be the same as the ratio of the cube of their heights:

or (5 1/2)*(5 1/2)*(5 1/2) / (3 1/2)*(3 1/2)*(3 1/3) = 166.4/42.9 = 3.88

So, the 2X6 will be about 4 times as rigid as the 2X4, or, the 2X4 will deflect about 4 times as much as the 2X6.
===

 

[Eric R.]

I find good baltic birch at a local place that recycles building materials. Lots of scraps from cabinet shops end up there - half or quarter sheets usually. It's what I used for my 25G Cube Reboot stand.
But to the question about unsupported spans - the key to a strong beam is DEPTH more than thickness. A 2x8 beam is stronger than two 2x4s sistered together. I forget who I'm quoting, but I've saved this for reference:
===
What you need to do to answer your question is to look at the term, I, which is the "Moment of Inertia" of the beam, and is dependent on the SHAPE of the beam.

For a solid rectangular beam, I = (b*h*h*h)/12
or, the width of the beam times the cube of it's height over 12.

So, all things being equal, the deflection of a 2X4 and a 2X6 under a given uniformly distributed load will be proportional to the calclulated values for I for the 2X4 and the 2X6. And, since the width of the beams is going to be the same (1 1/2 inches) in both cases, the ratio of the beam deflections will be the same as the ratio of the cube of their heights:

or (5 1/2)*(5 1/2)*(5 1/2) / (3 1/2)*(3 1/2)*(3 1/3) = 166.4/42.9 = 3.88

So, the 2X6 will be about 4 times are rigid as the 2X4, or, the 2X4 will deflect about 4 times as much as the 2X6.
===

Very interesting, good to know! Though if I did my calculation right, it's only about 15% stronger to increase the height of the beam (from 5.5" to 7.25") than it is to keep the height the same and double the width. Of course, I'm sure it's actually a bit more complicated when talking about real building materials than a solid hypothetical engineered beam.

 

[JoshH]

Here are pics of the stand I built for a 55g. Still needs doors, a sanding, and a good finish, just being test fit here. All 3/4" maple veneer ply.

Looks similar to my 125 build, but mine has additional cross braces, but I have a 30" wide tank.

All these stands are far overbuilt - you can sleep easy. Looks at what Aqueon sells for their 125-180 tanks, heck look at the IKEA like particle board stands all modern, rimless manufacturers ship with their tanks.

To be fair, any Red Sea or Waterbox Aquarium over 100 Gallons uses plywood and not particle board or MDF....

This is it right here.

As sleepydoc said, no one has verified numbers on plywood, so we're all sort of going with what we feel is strong enough.

But one metric we DO have is manufacturer built tanks from the likes of aqueon and red sea. It's seems like a safe assumption that these companies engineered their stands. If we could somehow compile dimensions for these stands at a few different common tank sizes, that would put a lot of this to rest.

I would probably take whatever red sea or aqueon uses as a minimum, make mine a touch beefier, and sleep easy Good call BZOFIQ

With large tanks I wouldn't follow Red Seas stand design after there 750 XXL debacle