Glass/Starphire questions

[Wasserpest]

I am checking around for a glass panel for a plywood tank that I am going to start building next year. Interesting... the prices quoted for that panel go from $250 to $700, it's crazy what you can save just by calling a bunch of different glass stores.

Anyway, two questions for those that have done something like this:

1) Is a polished edge necessary? They tell me that the tempering process will lead to edges that are not sharp, but some recommend polishing edges anyway, which adds around 15-17% to the price. Since it goes inside a plywood tank, I don't care about beveled edges, but not cutting my hand when scraping algae is always a nice detail.

2) The size of the panel is probably going to be 65x28. Do you think that a 1/2 in sheet would be safe, if it goes into a non-flexing plywood frame? I'd rather not go thicker, for weight, price, and distortion reasons. The tables I looked at don't specify whether the glass is tempered, and in my experience tempering adds a lot of strength to glass. Is it risky?

[helgymatt]

what is a plywood tank?

[moogoo]

^ a tank made of plywood with a single panel that is glass.

[helgymatt]

sorry to hijack this, but how does it hold water then? Some kind of sealant (roofing stuff...)?

[Wasserpest]

Here is some reading for ya: http://www.plantedtank.net/forums/di...onversion.html

Yes, it is sealed with Epoxy.

Now back to my glass questions.

[chuukus]

I would stay away from tempered glass I have heard so many bad things about it. I have seen a few plywood tanks made with 1/2" up to 400 gallons but im not sure how tall they were. Now if you made it 24" tall I would say for sure 1/2" is thick enough.

My plywood tank is 24"x96" with 1/2" starfire I havent filled the tank all the way yet but I have no worries about failure. I had the edges polished and beveled it didnt cost much I think you would be much happier with polished beveled edges then without.

It seems like I seen a diy plywood tank 580 gallons 96" long 48" deep 30" tall with 1/2 float glass IMO thats pushing your luck but it held water. So I would think 1/2" would be fine for your tank as long as the tank is built solid and doesnt flex. I will see if I can find the web page of the 580 gallon build for you to check out. There was some good documentation on that specific tank that might be of some help to you.

[Wasserpest]

Thanks chuukus... what bad things have you heard about tempered glass? I believe if you have a tempered and a non-tempered sheet of the same thickness, the tempered one is much stronger. Isn't that a good thing?

It's about $50 to have the edges polished... but I am not convinced that is necessary for a tempered piece, which has no sharp edges to begin with.

[Hoppy]

Tempered glass is much stronger than regular glass. I can't see how it would be dangerous to use it for the viewing panel in a plywood tank. Of course, you will want the plywood frame that holds it to be very stiff too, like reinforced with a steel angle. If it does break, it won't just crack and leak out the water. It will shatter into a thousand small pieces and the water will all leave in a second - a demonstration of a "flash flood".

[Craigthor]

Originally Posted by helgymatt

sorry to hijack this, but how does it hold water then? Some kind of sealant (roofing stuff...)?

Many Epoxy's are available. The most commonly used one is Sweet Water Epoxy, pricy but heards it works great. I was considering one at one point.

Originally Posted by Wasserpest

Thanks chuukus... what bad things have you heard about tempered glass? I believe if you have a tempered and a non-tempered sheet of the same thickness, the tempered one is much stronger. Isn't that a good thing?

It's about $50 to have the edges polished... but I am not convinced that is necessary for a tempered piece, which has no sharp edges to begin with.

Why Tempered? Hoppy brings up a good point that if it fails it will be a flash flood. Also I think 1/2" is only recommended up to 24" tall. There are alot of good calculators out. Google the GARF plywood tank one. It is a great site and has some good info and calculations along with cut sheets if you enter the dimensions of your tank.

Also check out hte DIY section over at Monsterfishkeepers.com for some great info. Those guys have built some huge tanks 15000g+ JohnPTC over there has some great knowledge along with others.

Craig

[rbarn]

Its the height of the water that determines pressure and glass thickness
not the total volume.

You could put a lake behind a 24" pane of glass, as long as water is only
24" deep, pressure does not change.

1/2" glass should be fine for a 24" deep tank.
MY 28" tall tank factory made tank only uses 1/2"

[jinx©]

Honestly I would think 1/2" would work in your case because of the framing method involved. I'm assuming you're basically cutting a window into plywood, like your original ply-tank, so the glass is actually supported quite a bit more than a typical rimmed tank build IMO.

The polished edges would be nice, but I think a piece of emery cloth could knock down any sharp edges well enough for your application considering the edges won't even be seen.

Tempered glass would stronger, but Hoppy has a valid point about on the differences in an event of a crack etc.

[Wasserpest]

Thanks for all the replies, very much appreciated!

Originally Posted by Hoppy

Tempered glass is much stronger than regular glass. I can't see how it would be dangerous to use it for the viewing panel in a plywood tank. Of course, you will want the plywood frame that holds it to be very stiff too, like reinforced with a steel angle. If it does break, it won't just crack and leak out the water. It will shatter into a thousand small pieces and the water will all leave in a second - a demonstration of a "flash flood".

My thoughts exactly. If I had the choice between a weak and a strong glass... well... the CHANCE that the strong glass shatters is much less.

Originally Posted by Craigthor

Many Epoxy's are available. The most commonly used one is Sweet Water Epoxy, pricy but heards it works great. I was considering one at one point.

I think the most commonly used is West Epoxy. Sometimes covered with Sweet Water Epoxy paint. Some folks use a non-epoxy coating and cover that with Sweet Water paint. Many choices.

Originally Posted by Craigthor

Why Tempered? Hoppy brings up a good point that if it fails it will be a flash flood. Also I think 1/2" is only recommended up to 24" tall. There are alot of good calculators out. Google the GARF plywood tank one. It is a great site and has some good info and calculations along with cut sheets if you enter the dimensions of your tank.

Well, tempered because of the increased strength mainly. Now regarding the flash flood. Imagine you stand in front of your tank, scrub that tough diatom algae, and the front panel breaks. Would you rather have it break into 1000 pieces ("security glass"), or have a few pointed pieces poke holes into you? Okay, most likely there will be just a crack, and in the ideal case you will have time to get the hose and drain the tank, still...

Originally Posted by Craigthor

Also check out hte DIY section over at Monsterfishkeepers.com for some great info. Those guys have built some huge tanks 15000g+ JohnPTC over there has some great knowledge along with others.

Craig

I checked many many plywood builds before I started mine, and you are right, there are some neat ones out there, and some showing what not to do. The most inspiring one for me was definitely this one: http://www.reefcentral.com/forums/sh...readid=1026436

Originally Posted by rbarn

Its the height of the water that determines pressure and glass thickness
not the total volume.

You could put a lake behind a 24" pane of glass, as long as water is only
24" deep, pressure does not change.

1/2" glass should be fine for a 24" deep tank.
MY 28" tall tank factory made tank only uses 1/2"

I disagree with you a bit, I think there IS a change of pressure as tanks get wider. Imagine a tank that is only 1 inch wide, you could build that very tall with very thin glass. As you add more depth (not height), the pressure increases. Of course there is not much change going from say 28" depth to 32" depth. But I think there is some noticeable change when you go from 12" (typical 55gal) to say 24", and the calculators I have seen do not take that into account.

Originally Posted by jinx©

Honestly I would think 1/2" would work in your case because of the framing method involved. I'm assuming you're basically cutting a window into plywood, like your original ply-tank, so the glass is actually supported quite a bit more than a typical rimmed tank build IMO.

The polished edges would be nice, but I think a piece of emery cloth could knock down any sharp edges well enough for your application considering the edges won't even be seen.

Tempered glass would stronger, but Hoppy has a valid point about on the differences in an event of a crack etc.

Thanks for confirming what I was thinking... again, stronger glass = will not crack, so perhaps no issue. When I took the hammer to my 55 gal tank, I was amazed how strong the tempered bottom really was, compared to the non-tempered sides.

[Hoppy]

The water pressure depends only on the height of the tank, and even then, the pressure is maximum only at the bottom of the tank. But, the length of the glass panel is very significant. The longer it is, the more it tries to bend from the water pressure. That's why long tanks have the center brace across the top. But, if you stiffen the plywood frame, preferably with steel angles or channels, the glass won't be subjected to the bending.

[lumpyfunk]

Wasserpest,

That garage tank didnt take long to get you going on the indoor one! Is this one going to be 71 inches by any chance?

I cant wait to follow the build thread you do for this one!

[Wasserpest]

Yep, 71 inchers, how do you know???

Before I really get started on this one, I have to take down the 100gal tank that sits there right now, remove the carpet, add tile... The latter two things are going to happen in November/December in almost the entire house, so you'll have to wait for a new plywood build thread until sometimes, hopefully early, next year...

But that won't keep me from drawing plans, asking question, and collecting parts early on.