Hello there,

I have just been given a tank 200cm long, 60cm high, 40cm wide and is made fo 8mm plate glass. I understand for a tank this size 8mm is not safe. However if I were to fill it upto about 35cm or 40cm then will it be safe? Is it the same as having a tank 35cm or 40cm high? If I fixed a couple of braces on top, how high can it be filled safely?

Thank you.

if you run your braces correctlly you should not have any problems at all,

ie run bracing 50mm strips around the inside top of tank and then your cross braces,three across at 500mm spacing should do it nicely,if your not sure,just go and look at some tanks in the shops and you will be able to see for your self how to do yours.

hope this helps you out

I'd go for 75mm wide strips, we are talking about a lot of force here. Have done the calcs on 8mm glass assuming bracing as suggested above (but 75mm wide all round instead).

You will have a safety margin of only 150% on the front and back glass. It is risky having a tank this big and long made only from 8mm glass. There are many tanks like it around with no problems at all however. You will probably get away with it since most others seems to.

You will have to make a very good stand for it though and make sure the top surface is very level (less than 1mm curvature in any direction) or you will risk creating a stress in the glass that will use up that 50% headroom you have.

If you only fill the tank to 550mm it will increase the safety to around 200% and 500mm to 265%. It's not the same as having a shorter tank but the forces on the glass will be lowered by enough to give a very good safety margin. The glass thickness has a cube-law relationship to depth so it only takes a small drop in the water level to significantly improve the safety margin in the glass.

hey warren

did you culculate as 8mm float glass or as 8mm plate as there is a big difference between the two types of glass

not being picky just curious thats all

Plate glass is float glass as far as I know...

lol no they are different

Plate Glass

Used in the past to produce higher quality glass, this technology was completely outperformed by the float glass process

Float Glass

A term for perfectly flat, clear glass (basic product). The term "float" glass derives from the production method, introduced in the UK by Sir Alastair Pilkington in the late 1950's, by which 90% of today's flat glass is manufactured.

ok here's the site for ya

http://www.glassonweb.com

so any way thats why i was wondering which you used to calculate as 8mm plate is very strong,i.e. no wobbles in it unlike float glass

Ok, just a bit of research:

Plate glass is approximately 4% stronger in ultimate tensile strength than float glass. Couldn't find the difference in the process to make it but who cares.

The term 'quality' seems only to refer to the flattness...

The problem with plate glass is it is not anealed like float glass is and it has more air bubbles in it. It's primary purpose is for mirrors as it is flatter than float glass although the human eye can see little difference straight-on. It has a much higher level of internal stress than float glass and is less suitable for structural purposes. The internal stress makes the plate glass less strong overall.

Am am actually wandering if the tank is made of plate glass at all or if it was just a term used by Tetraman, like plates of glass or panes of glass...