Calling all engineers!!

Sisterlimonpot · 04/12/2018, 07:46 PM

I'm well along with a build for my 300g in-wall tank. I'm about to start building the stand (out of wood) and need some engineering guidance.

My tank is 96" long 30" deep and 24" tall. the front of the tank will be sitting on 2x6 rails with 2x4 uprights every 16".

Plenty of support up front, here's where I need the help of the engineers, for the back of the tank I want to have it completely open, which means the top rails are going to have to be pretty beefy. What do I need to carry the weight of the 300g and have very little (or within acceptable limits) deflection on that top beam?

Thanks for reading.

LT72884 · 04/12/2018, 08:29 PM

Dang, 300g is alot of water weight. You might need more than just 2x4s up front to support that kind of weight.

Sent from my SM-S920L using Tapatalk

FullBoreReefer · 04/12/2018, 08:33 PM

Is the tank gonna hang back into that doorway?

Sisterlimonpot · 04/12/2018, 09:52 PM

Quote:

Originally Posted by FullBoreReefer

Is the tank gonna hang back into that doorway?

No, It will be flush with the jamb.

Sisterlimonpot · 04/12/2018, 09:59 PM

this is where I'm at now, the stand will bolt right up to the wall into the 2x6s, which means the stand that I will build will only need to be 25.25" wide (the wall is 4.75" wide)

sus · 04/12/2018, 10:40 PM

Quote:

Originally Posted by LT72884

Dang, 300g is alot of water weight. You might need more than just 2x4s up front to support that kind of weight.

Sent from my SM-S920L using Tapatalk

I wouldn’t be worried about the front. 2x4’s at 16” oc is plenty strong. Think about load bearing walls which take much more weight than a fish tank. Each 2x4 here is only taking like 200-250 lbs.

It’s gonna be tough to span 8’ in the back with little to no deflection using timber. Can you live with one midspan post?

ClownNut · 04/13/2018, 06:28 AM

Quote:

Originally Posted by LT72884

Dang, 300g is alot of water weight. You might need more than just 2x4s up front to support that kind of weight.

Sent from my SM-S920L using Tapatalk

no you dont. each 2x4 will take 600+ lbs to buckle it.
he got 8 across the front. only half of that should able to hold up the whole tank as long as within reasonable height.
as for the back. 2x8 across the 8" span should able to hold it up no problem.

sus · 04/13/2018, 06:54 AM

Quote:

Originally Posted by ClownNut

no you dont. each 2x4 will take 600+ lbs to buckle it.

he got 8 across the front. only half of that should able to hold up the whole tank as long as within reasonable height.

as for the back. 2x8 across the 8" span should able to hold it up no problem.

You’re saying a single 2x8 is ok to span the 8’ across the back? What are you basing this on? Did you check the deflection, moment, shear, etc... or are you just assuming it would work?

FullBoreReefer · 04/13/2018, 07:01 AM

What about a coated steel I-beam, or square tube? Then you could rest it on a 4x4 on each corner maybe?

...I am no engineer, just thinking out loud for alternate options

ClownNut · 04/13/2018, 07:31 AM

Quote:

Originally Posted by sus

You’re saying a single 2x8 is ok to span the 8’ across the back? What are you basing this on? Did you check the deflection, moment, shear, etc... or are you just assuming it would work?

i used the whole water weight. as distributed load (5185n/m) on the 2X8 across 8'

i got 5E-4m deflection. i will call that 0.

sus · 04/13/2018, 07:51 AM

Quote:

Originally Posted by ClownNut

no you dont. each 2x4 will take 600+ lbs to buckle it.

he got 8 across the front. only half of that should able to hold up the whole tank as long as within reasonable height.

as for the back. 2x8 across the 8" span should able to hold it up no problem.

Just to follow up now that I’m at work and can run some calcs.
- assuming tank weighs 500 lbs empty
- you’re looking at a distributed load on that back beam of ~188plf
- using a single 2x8 spruce pine fir would yield .25” of deflection.
- it is also overloaded in bending moment.
- if you used double 2x8’s you could half the deflection (assuming you’d glue/screw them together well)
- not sure about you, but I’m not comfortable with 1/8” deflection on a glass tank. I’d want 0” period (had a tank crack recently)

This is over simplified analysis and assumes you’re putting load directly on the timber. Where really, in order for the timber to deflect, the glass has to deflect. I just wouldn’t want to put that kind of stress on the glass/joints personally. If it were me, I’d either build it all out of steel, or find a way to add midspan support.

This is just my opinion. I’m by no means a timber design expert but I do come across it somewhat frequently as a Civil PE

sus · 04/13/2018, 08:20 AM

Quote:

Originally Posted by ClownNut

i used the whole water weight. as distributed load (5185n/m) on the 2X8 across 8'

i got 5E-4m deflection. i will call that 0.

Can you share your calculations?

Applying a 2.6kn/m load (half will go to the front) to a 2.44 m long steel W8x10 will still yield a .5mm deflection. So something you are doing is just not right if you are coming up with 0...

ClownNut · 04/13/2018, 08:33 AM

Quote:

Originally Posted by sus

Can you share your calculations?

Applying a 2.6kn/m load (half will go to the front) to a 2.44 m long steel W8x10 will still yield a .5mm deflection. So something you are doing is just not right if you are coming up with 0...

i recheck my math, i got -.01m = 1cm deflection. too early in the morning to do math. lol i rounded up on most number. 1/3 an inch deflection.
PM you too, i want to see how do you comes up to your number.

Sisterlimonpot · 04/13/2018, 09:44 AM

Quote:

Originally Posted by sus

Just to follow up now that I’m at work and can run some calcs.
- assuming tank weighs 500 lbs empty
- you’re looking at a distributed load on that back beam of ~188plf
- using a single 2x8 spruce pine fir would yield .25” of deflection.
- it is also overloaded in bending moment.
- if you used double 2x8’s you could half the deflection (assuming you’d glue/screw them together well)
- not sure about you, but I’m not comfortable with 1/8” deflection on a glass tank. I’d want 0” period (had a tank crack recently)

This is over simplified analysis and assumes you’re putting load directly on the timber. Where really, in order for the timber to deflect, the glass has to deflect. I just wouldn’t want to put that kind of stress on the glass/joints personally. If it were me, I’d either build it all out of steel, or find a way to add midspan support.

This is just my opinion. I’m by no means a timber design expert but I do come across it somewhat frequently as a Civil PE

Not that I've ruled out the possibility of steel, it just means I have to find someone that can build it for me. I'm the kind of guy that wants to do everything myself...

What would you think if I ordered a 5"x8"x96" glue laminate? That should be able to hold up 2 or 3 of my tanks???? Just guessing of course.

sus · 04/13/2018, 09:58 AM

Quote:

Originally Posted by Sisterlimonpot

Not that I've ruled out the possibility of steel, it just means I have to find someone that can build it for me. I'm the kind of guy that wants to do everything myself...

What would you think if I ordered a 5"x8"x96" glue laminate? That should be able to hold up 2 or 3 of my tanks???? Just guessing of course.

I don’t have much experience with glue lams. I’m sure whoever you ordered one from could tell you the bending capacity though.

Sisterlimonpot · 04/13/2018, 11:45 AM

Sus and clown nut, thank you for your expertise,

Quote:

Originally Posted by sus

I don’t have much experience with glue lams. I’m sure whoever you ordered one from could tell you the bending capacity though.

When it comes to bending capacity, educate me on what I need to know. At 96" will they just give me deflection at a certain a weight? or is there going to be a number associated with agiven type of laminate?

And to make sure we are on the same page, (correct any of this that you see wrong) 300g of saltwater is roughly 2600 lbs and i'd agree with you that 500 lbs is a liberal estimate for the tank. total of 3100 lbs, half the weight held up by the front which means i'm concerned with a load of 1550 lbs that this beam has to hold (at a minimum).

sus · 04/13/2018, 11:53 AM

Quote:

Originally Posted by Sisterlimonpot

Sus and clown nut, thank you for your expertise,

When it comes to bending capacity, educate me on what I need to know. At 96" will they just give me deflection at a certain a weight? or is there going to be a number associated with agiven type of laminate?

And to make sure we are on the same page, (correct any of this that you see wrong) 300g of saltwater is roughly 2600 lbs and i'd agree with you that 500 lbs is a liberal estimate for the tank. total of 3100 lbs, half the weight held up by the front which means i'm concerned with a load of 1550 lbs that this beam has to hold (at a minimum).

If they could tell you the deflection based on the load of 194plf (1550 lbs/ 8ft) that would be great. I’m guessing though they will just give you a moment capacity. If you are able to get that, along with shear capacity, EI value, and allowable end reaction (with bearing length) then you can calculate the deflection and verify if it works or not.

sus · 04/13/2018, 11:56 AM

And to answer your second question, yes you are seeing that right. 2600 is probably a bit conservative but better to be on the conservative side

sus · 04/13/2018, 12:22 PM

If you could find a beam with an EI value in the 270x10^6 that would equate to roughly a 1/16” deflection.

This value is similar to that of a double 2x10 spruce pine fir.

AnnaCassandra · 04/13/2018, 01:12 PM

If you wanted to use a steel beam to save on the size of wooden beam, could you not bolt it to the wooden stand? and otherwise construct it out of wood?

Sisterlimonpot · 04/13/2018, 02:07 PM

Quote:

Originally Posted by AnnaCassandra

If you wanted to use a steel beam to save on the size of wooden beam, could you not bolt it to the wooden stand? and otherwise construct it out of wood?

Excellent question.... Anyone care to take it

??

ClownNut · 04/13/2018, 02:14 PM

also keep in mind, because the pine is not isotropic. i dont know how much of the result can be trusted.

sus · 04/13/2018, 02:20 PM

Quote:

Originally Posted by ClownNut

also keep in mind, because the pine is not isotropic. i dont know how much of the result can be trusted.

Huh? Not sure what you’re getting at

sus · 04/13/2018, 02:23 PM

Quote:

Originally Posted by Sisterlimonpot

Excellent question.... Anyone care to take it

??

For sure you could. Not sure what your using for your verticals. may be tricky to come up with a good connection between the two depending on which beam.

Lsufan · 04/13/2018, 10:49 PM

How much head room are u looking for? It looks like u built the wall around 42” tall, so if u use a double 2 X 10 it will leave u with about 32” to 32.5” of head room. If u want more then that then u may need to go with steel. U could also come in about 2’ from one end with a support, then u would only have a 6’ span & a double 2 X 8 would work & give u a little more head room.

I’m no engineer & I didn’t calculate to see if a double 2X10 would work, I was just using it as a example as far as how much head room u would have. I know I wouldn’t use anything less then that to span the entire 8’.

04/12/2018, 07:46 PM	#1
Sisterlimonpot R.C. Fraternity President Join Date: Dec 2008 Location: Litchfeild Park AZ Posts: 11,490 Blog Entries: 2	Calling all engineers!! I'm well along with a build for my 300g in-wall tank. I'm about to start building the stand (out of wood) and need some engineering guidance. My tank is 96" long 30" deep and 24" tall. the front of the tank will be sitting on 2x6 rails with 2x4 uprights every 16". Plenty of support up front, here's where I need the help of the engineers, for the back of the tank I want to have it completely open, which means the top rails are going to have to be pretty beefy. What do I need to carry the weight of the 300g and have very little (or within acceptable limits) deflection on that top beam? Thanks for reading. __________________ Jimmy MASVC President Dishes are done man! Current Tank Info: 300 in progress

04/12/2018, 08:33 PM	#3
FullBoreReefer Registered Member Join Date: Jul 2010 Location: Wooster, OH Posts: 1,862	Is the tank gonna hang back into that doorway? __________________ 60x36x24 mixed reef. 40b sump. Regal 250int Varios. 4xHydra26HDs+t5s. 4xMp40wes. Apex2016.

04/12/2018, 09:59 PM	#5
Sisterlimonpot R.C. Fraternity President Join Date: Dec 2008 Location: Litchfeild Park AZ Posts: 11,490 Blog Entries: 2	this is where I'm at now, the stand will bolt right up to the wall into the 2x6s, which means the stand that I will build will only need to be 25.25" wide (the wall is 4.75" wide) __________________ Jimmy MASVC President Dishes are done man! Current Tank Info: 300 in progress

04/13/2018, 07:01 AM	#9
FullBoreReefer Registered Member Join Date: Jul 2010 Location: Wooster, OH Posts: 1,862	What about a coated steel I-beam, or square tube? Then you could rest it on a 4x4 on each corner maybe? ...I am no engineer, just thinking out loud for alternate options __________________ 60x36x24 mixed reef. 40b sump. Regal 250int Varios. 4xHydra26HDs+t5s. 4xMp40wes. Apex2016.

04/13/2018, 02:14 PM	#22
ClownNut Registered Member Join Date: Sep 2004 Location: Minnesota Posts: 1,859	also keep in mind, because the pine is not isotropic. i dont know how much of the result can be trusted. __________________ Dont let me know where u lived if u have a nice pair of clownfish in ur tank!^_^ Clown kidnaper^_^ Current Tank Info: 300DD, SM200/RD3,ATI 60-8X80+4X75, 2 Sea Sweep & 4X6105 & 6208

04/12/2018, 08:29 PM	#2
LT72884 Registered Member Join Date: Feb 2018 Posts: 13	Dang, 300g is alot of water weight. You might need more than just 2x4s up front to support that kind of weight. Sent from my SM-S920L using Tapatalk

04/13/2018, 11:56 AM	#18
sus Premium Member Join Date: Nov 2007 Location: Arvada Colorado Posts: 606	And to answer your second question, yes you are seeing that right. 2600 is probably a bit conservative but better to be on the conservative side

04/13/2018, 12:22 PM	#19
sus Premium Member Join Date: Nov 2007 Location: Arvada Colorado Posts: 606	If you could find a beam with an EI value in the 270x10^6 that would equate to roughly a 1/16” deflection. This value is similar to that of a double 2x10 spruce pine fir.

04/13/2018, 01:12 PM	#20
AnnaCassandra Registered Member Join Date: Dec 2015 Location: Edmonton, Alberta Posts: 100	If you wanted to use a steel beam to save on the size of wooden beam, could you not bolt it to the wooden stand? and otherwise construct it out of wood?

04/13/2018, 10:49 PM	#25
Lsufan Registered Member Join Date: Nov 2013 Location: Baton Rouge Posts: 1,410	How much head room are u looking for? It looks like u built the wall around 42” tall, so if u use a double 2 X 10 it will leave u with about 32” to 32.5” of head room. If u want more then that then u may need to go with steel. U could also come in about 2’ from one end with a support, then u would only have a 6’ span & a double 2 X 8 would work & give u a little more head room. I’m no engineer & I didn’t calculate to see if a double 2X10 would work, I was just using it as a example as far as how much head room u would have. I know I wouldn’t use anything less then that to span the entire 8’.