Plywood Tank Questions

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S

Sham

Feeder Fish
MFK Member
Dec 7, 2006
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Townsville Australia
Hi guys l'm looking at building a plywood tank using two sheets of glass for the front window.
Tank dimensions are W 80" H 35" D 24" The two sheets of glass are half inch thick is that thick enough for this size tank ?
To my way of thinking using two sheets of glass for a large area would be stronger then one large sheet am I right or dreaming on this one ?
I need to know this before I go purchasing the glass which is at a house demolition yard.

Sham
 
Guess I should have been clearer. I have used the garf site calculator for a number of weeks. The calculator on the garf site does not go over 24", I want a tank height of 35" as that is the size of the glass I have picked out for the job. Just want to know if the half inch thick is thick enough for 35" height. Searched the internet and read most of the posts about plywood tanks on this forum. Glass thickness once the tank goes over 24" seems to be a bit of a grey area. Also I want to use two pieces of glass to make the front window.

Sham
 
Ok a bit more seaching on the forum and I am of the conclusion if this was one sheet of glass it would be way to thin. So does it make a difference that I will be using 2 sheets with a join as going by glass thickness tables half inch would be safe for that depth in that length if it was two single tanks. Also since the timber frame will be covering 3 inches of glass top bottom and sides do I take the glass measurements from those support areas to workout the thickness ?

Sham
 
You use the "window" size to calculate the safety factor. But keep in mind that then you only fill the tank to the window height... filling it higher throws the safety factor out the window... so to speak.
My worry about your design is the join between the 2 windows... remember that on the left and right you'll have the sides supporting/bracing your windows frame with a right angle join... How will you create that same rigidity in the middle? IMO you'll need at least a vertical 4"x4" from top to bottom of the tank, to support your window frame in the middle of the tank.

Get Google Sketchup and draw us a picture :popcorn: the idea sounds interesting and doable.
 
I have pretty much decided to go ahead with the tank. Found two tanks similar design to what I have in mind. One had a ply front with the two glass panes and the other had a pine front.
I will be going with a 4x2 pine front frame and ply for the rest of the tank. I now believe the glass is thick enough for what I have in mind and with the strength of the timber I will be using should be safe enough. A poster called Lomax made a very similar tank which is posted on another forum. Same thickness glass as mine and near enough to the same height. The water level will not be going above the glass. Actually will be around 2" below the glass edge.
Thanks for the help

Sham
 
You did remember the responsibity you took on when you registered with this forum didn't you??


We want ot see pix of the build !!!!!! :D

Dr Joe

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I expect that double panes of glass will be a pain.
Double glass window are sealed with special designs , the space is then purged, evacuated and filled with inert gas. My experience is that if the seal fails the glass gets dirty with condendation and dust.
Avoid "old" glass, as it gets >20 yr old it gets more brittle/ lower fracture toughness.
 
A little late now to go back as I have bought the glass. I think you misunderstand what I am going to do. The glass will not be stuck on top of each other. It will be end to end so I have a larger viewing area. Doing this due to the economics of the project. Single slab of glass the size this pair make would cost me at least $700 down here in the land of Oz. I got the pair for $140 so to me making a frame suitable to to house the glass is worth the effort. Also having a joiner running vertically down the middle of the tank is not a problem for me either. I know some people wouldn't like that but I have to live with it so...........
At this stage still working out what timber to use. Should be purchasing the timber in the next few days and starting the project :D
Also looking at the epoxy resins. I can get west systems resin which I see a few builders using , can get epoxy swimming pool paint which is a nice blue colour or I can go with an epoxy that is specifically for potable water.
Any comments ?
 
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