Question on strength of glass for 115G - The Planted Tank Forum
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post #1 of 12 (permalink) Old 01-16-2016, 12:46 AM Thread Starter
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Question on strength of glass for 115G

Hey guys,

Last summer I picked up some glass from a guy off craigslist. Basically it is a disassembled tank with a volume of around 115 gallons. It's been sitting in my shed since. I am planning on doing some work in the garage this weekend, one part of that is building some shelving across the entire side of the garage, and Ive just incorporated a stand for what would be my tank.

Anyway I really want to get the ball rolling on this tank, and I also want it to be an entirely DIY project, with the except of a heater.

I start with a couple questions regarding building the tank itself. I have never built a tank before so I could use some pointers.

Also the glass is 1/2 thick. Do I need to brace it, and if so where are how? Consider I could care less about looks as this is going to be a garage tank, where I can collect local fish.

Thanks guys, I appreciate any advice you can provide.

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post #2 of 12 (permalink) Old 01-16-2016, 03:05 AM
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plenty of youtube vids available for building tank... all you need, is silicone, tape, and an extra set of hands for a larger tank.

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post #3 of 12 (permalink) Old 01-16-2016, 03:26 AM
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Be careful with the silicone you use. GE1 doesn't have the shear strength needed on that size tank.

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post #4 of 12 (permalink) Old 01-16-2016, 03:35 PM
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Garage projects are good as it does free our minds to use some things that don't work for pretty. I don't build from scratch on tanks but if I were in this situation, I might look at using aluminum angle around the bottom for a couple reasons. One is to hide the edge so that rougher can be okay and also to give a bit of elevation for the lower glass as I don't like it resting on the stand for the full surface. Too easy for a small lump of something to wind up pressing up? Good silicone for sure but a trim is often expected for me.
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post #5 of 12 (permalink) Old 01-16-2016, 05:45 PM
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What really matters is the height and length (other factors become important when you start getting larger).
What are the dimensions?

Depth effects the pressures that will be seen at the seams and on the glass.
Length matters due to bowing from those pressures.

As far as silicone goes, the Momentive 100 series has really high holding strength, as does SCS 1200, and another that is escaping me right now. I'll have to see if I can find that one as it is specifically manufactured for aquariums (not the stuff you get at the pet shop, that stuff is extremely weak and is probably too old to be useful). Dow also makes one that is good. People use the stuff from the big box stores, but I've looked up the data sheets and they really don't have good bonding strength or tear strength and the shear strength is abysmal. It isn't designed for structural adhesion, it is for sealing joints to make them liquid tight. That and if you get the wrong stuff you can wipe out your tank from inhibitors.
The Momentive 103 is black, 108 is clear, I believe 106 is red and there is a blue as well as white.

As far as the base goes, put a neoprene mat down, or go with a yoga mat or foam board. It will even out the pressures on the bottom glass and prevent (small) imperfections in the surface of your stand from blowing out the glass. You will need a flat level surface for your stand to completely support the bottom of the tank, you can't build it to support only the perimeter. Unless you build it with a raised bottom, in that case you would need a trim of some sort that would help support the seam along the bottom glass like the mass produced tanks do as the seam will be seeing high shear stresses, which is the weakest type of joint for silicone.
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post #6 of 12 (permalink) Old 01-16-2016, 07:05 PM
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Quote:
Originally Posted by Beer View Post
What really matters is the height and length (other factors become important when you start getting larger).
What are the dimensions?

Depth effects the pressures that will be seen at the seams and on the glass.
Length matters due to bowing from those pressures.

As far as silicone goes, the Momentive 100 series has really high holding strength, as does SCS 1200, and another that is escaping me right now. I'll have to see if I can find that one as it is specifically manufactured for aquariums (not the stuff you get at the pet shop, that stuff is extremely weak and is probably too old to be useful). Dow also makes one that is good. People use the stuff from the big box stores, but I've looked up the data sheets and they really don't have good bonding strength or tear strength and the shear strength is abysmal. It isn't designed for structural adhesion, it is for sealing joints to make them liquid tight. That and if you get the wrong stuff you can wipe out your tank from inhibitors.
The Momentive 103 is black, 108 is clear, I believe 106 is red and there is a blue as well as white.

As far as the base goes, put a neoprene mat down, or go with a yoga mat or foam board. It will even out the pressures on the bottom glass and prevent (small) imperfections in the surface of your stand from blowing out the glass. You will need a flat level surface for your stand to completely support the bottom of the tank, you can't build it to support only the perimeter. Unless you build it with a raised bottom, in that case you would need a trim of some sort that would help support the seam along the bottom glass like the mass produced tanks do as the seam will be seeing high shear stresses, which is the weakest type of joint for silicone.
Very good answer from you, sir !
I also like your tagline. What use is an answer that is only half complete. If a person doesn't have time for a full answer, why does he have time to waste on a forum to start with?
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post #7 of 12 (permalink) Old 01-16-2016, 07:27 PM
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Disney uses the DC 795 for their tanks.

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post #8 of 12 (permalink) Old 01-17-2016, 02:46 AM Thread Starter
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Quote:
Originally Posted by Beer View Post
What really matters is the height and length (other factors become important when you start getting larger).
What are the dimensions?

Depth effects the pressures that will be seen at the seams and on the glass.
Length matters due to bowing from those pressures.

As far as silicone goes, the Momentive 100 series has really high holding strength, as does SCS 1200, and another that is escaping me right now. I'll have to see if I can find that one as it is specifically manufactured for aquariums (not the stuff you get at the pet shop, that stuff is extremely weak and is probably too old to be useful). Dow also makes one that is good. People use the stuff from the big box stores, but I've looked up the data sheets and they really don't have good bonding strength or tear strength and the shear strength is abysmal. It isn't designed for structural adhesion, it is for sealing joints to make them liquid tight. That and if you get the wrong stuff you can wipe out your tank from inhibitors.
The Momentive 103 is black, 108 is clear, I believe 106 is red and there is a blue as well as white.

As far as the base goes, put a neoprene mat down, or go with a yoga mat or foam board. It will even out the pressures on the bottom glass and prevent (small) imperfections in the surface of your stand from blowing out the glass. You will need a flat level surface for your stand to completely support the bottom of the tank, you can't build it to support only the perimeter. Unless you build it with a raised bottom, in that case you would need a trim of some sort that would help support the seam along the bottom glass like the mass produced tanks do as the seam will be seeing high shear stresses, which is the weakest type of joint for silicone.
The external dimensions of the tank are: 6' Length 19" Width 22" Height
Again the panes are 1/2"

I didn't consider to use a special type of silicone for the tank. I was planning on using just some GE Silicone II. But I agree with your logic, I used that stuff for sealing showers now adhering them together.

GE SCS 1200 has a good price on amazon, I will probably go with that one. Do you think 4 tubes will do that job?

I just built the stand area today, very basic, made entirely from 2x4's. Where I was planning on putting the tank is level double 2x4 around the perimeter with 2 double cross supports. A ruff top down view below. I can easily slap down a 3/4" sheet of ply on the top of that to make a perfectly flat surface, if that's necessary.
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post #9 of 12 (permalink) Old 01-18-2016, 12:20 AM
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GE II has mildewcides in it.

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Quote me as saying I was misquoted.
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Here's to our wives and sweethearts - may they never meet.
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post #10 of 12 (permalink) Old 01-18-2016, 03:54 AM
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Marine Silicone | Sealants | Products | Bostik

This is my favourite, but I think it is a local market product.

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post #11 of 12 (permalink) Old 01-19-2016, 10:49 AM
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1/2" on that tank is crazy. It probably would still do better with a center brace, IMO. I would probably do a center brace and braces on the ends made of glass. As for the stand, I would add several braces from front to back and a sheet of plywood on top compared to the traditional rimmed tank stands you see on here. I would also add the foam board or yoga mat, trimmed and/or painted. While you are building it, I would drill it for a bean animal overflow on one of the short sides. Just my opinion again, but now would be the best time to do it.


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post #12 of 12 (permalink) Old 02-15-2017, 05:55 PM
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If it is overkill, why brace it?

By 1/2" is that slightly undersized 12mm or slightly oversized 13mm? There aren't many US glass manufacturers left, most plate glass is imported and is in metric dimensions. 12mm is appropriate for that tank with a safety factor of 4. 13mm will be slightly better. I lost my links to some really good information that had all of the engineering equations accounting for stresses, took into account weaker glass, variations due to width (it doesn't change the forces seen, but it effects the corner joints), and calculated how deflection you should end up seeing when the tank is filled. I also used to have links from professional journals and white papers from the glass industry that discussed aquarium construction. That is what I get for not backing up my links.

I'd probably go 13mm low iron as low iron is slightly weaker, but I love how clear the glass is. Not having that green tint is amazing. But that may also make the tank prohibitively more expensive.

As far as the RTV goes, what size tubes are you talking about? You should be going with the caulking gun size (I forget the volume of those) as a squeeze tube would take to long and the RTV would start forming a skin that would reduce the bond strength. Not to mention the cramps you would get in you hand and forearm by the time you had the first bead down.

Quote:
Originally Posted by Nordic View Post
Marine Silicone | Sealants | Products | Bostik

This is my favourite, but I think it is a local market product.
They don't have a MSDS or data sheet readily available. No idea what the bond, tear, or shear strength of that stuff is.

Bostik is a US based company, but it doesn't appear that they distribute the aquarium silicone in the US.

I usually feel kind of guilty using the quick reply... my replies are rarely quick.

Last edited by Darkblade48; 02-16-2017 at 10:20 AM. Reason: Please use the edit function for back to back posts to keep threads cleaner
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