Engineers and experts needed:) normal vs toughened glass

[smidey]

And then there's earthquakes. An earthquake with a peak ground acceleration of 2 Gs laterally(About chch quake sized) would effectively drop the safety factor of any tank by 2. So anything under 3 would drop to under 1. Assuming nothing else broke or slipped. But that's pretty significant.

i didn't say that

[henward]

i am weighing up now.

getting an all glass build 15mm glass

3m x 1.2 x 80 with a metal stand of 40 cms from the ground, total height of 1.2 metres (eye height for lazy boy viewing)

vs a ply build of approx same size.

the cost of the stand and tank approx will be $4k for all glass option.

i wonder how much the ply option will cost?

any estimate for me, i am not the most experienced with this.

[David R]

i wonder how much the ply option will cost?

any estimate for me, i am not the most experienced with this.

Go get a price per M for H3 treated 90x45, and for the sheets of ply you need, and work out how much timber you'll need. No idea what fibreglass costs but it shouldn't be too difficult to come up with a rough estimate.

Might have to hit up your guy for a price for my steel stand as HFF can't get them any more (currently looking for a new supplier).

[henward]

Go get a price per M for H3 treated 90x45, and for the sheets of ply you need, and work out how much timber you'll need. No idea what fibreglass costs but it shouldn't be too difficult to come up with a rough estimate.

Might have to hit up your guy for a price for my steel stand as HFF can't get them any more (currently looking for a new supplier).

yeah i will do that, i have already started to estimate the costs.

and judging by the costs, both will be very similar! the only way ply tank is going to be worth while in terms of value for money is if you build HUGE.

i mean HUGE.

my original 3x1.2x1.2 idea then its worth while. But the problem there is glass, you cant get glass thcik enough!!

I have based stand cost on a shorter stand, less steel at 40cm high, total height of 120cm tank and stand total.

tank 3x1.2x80cm.

got a quote for a tank, $2800 built on site, sump built on site, though thtas irrelevant cos it wont go under the stand but saves on time and transport.

stand is approx $1200 to $1300 powdercoated.

[blueether]

just a question, does the glass have to go all the way to the bottom, you could easy have the glass start 150 - 200mm up the front panel if the bottom of the panel had no (or very little) deformation.

correct me if I'm wrong but then you only have to take into account the hight of the water 'on' the glass:

|

|

| <= Glass 800mm

|

|

||

|| <<= wood 200mm

================ <= Base

[ilwis]

just a question, does the glass have to go all the way to the bottom, you could easy have the glass start 150 - 200mm up the front panel if the bottom of the panel had no (or very little) deformation.

correct me if I'm wrong but then you only have to take into account the hight of the water 'on' the glass:

|

|

| <= Glass 800mm

|

|

||

|| <<= wood 200mm

================ <= Base

yes i wouldnt have a problem with that but who is really going to have 200mm of substrate in a tank only 800 high it will turn your tank into a long 600mm tank

or by way of your picture it wouldnt change the ammount of pressure the glass has to withstand

just as a note about safety factors, a safety factor of 2 is standard a safety factor of 3 or more is considered unnessary excess its like building a coffee table with 6 legs when its just a square table

also something to think about:

in the past i made a coffee table fish tank

basically i made the tank out of decking timber for the sides and a flat but of thin MBF as the base supported by more decking timber (the mbf was only 2mm)

i then lined the inside with that clear plastic you get for your garden 2 layers thick 1 layer for incase it perished the other to hold the water

this worked well held water for years and i sold it 2 weeks ago (ive had a long fin eel and some other small fish cant remember what they were but about $2 each)

you could consider making your tank of ply then lining it with the thicker sheet plastic then all you have to do is seal where the sheets meet and where it meets the glass the ply is holding the pressure all its doing is suplying a water seal.

to do the top edges you get a thin bit of wood but the plastic between the ply and the wood folded over a few times for strength and tack (small nail) it up with a bunch of them or just staples if your so inclined

if you think its still too risky being plastic consider this

http://www.trademe.co.nz/home-living/ou ... 239733.htm

its just a plastic and holds a heap more water than what your looking at all you need to do is get the seals correct and the silicone you would use for any other tank would be able to stick to both the plastic and the glass, so that basically eliminates the cost of the fibreglass giveing you more money for glass and fish

[Warren]

i don't know what the calcs or the reasoning behind it being 12mm are, it was made professionally so perhaps the glazier has made them this way before and there have been no issues.

when creating a calculator like that with so many different potential entries and outcomes perhaps it is over/under calculated for the "ass covering" factor of the creator, not sure but what i do know is in real life that tank is made, full and hasn't blown to bits so perhaps it is safer than the calc program tells us. thinking about how i would make that calculator, I do wonder how they have factored in the top bracing. maybe the calc formula doesn't allow for that.

there are few experiences i have had in the building industry and also experiences my old man has had in civil construction with engineers that are totally unbelievable either "under engineered" or so far "over engineered" it makes you think they are not up to the job so it will be interesting to see if anything bad happens to that tank. I don't think there will be but time will tell.

Notice the link in the image: http://www.fnzas.org.nz/?p=1732

The calculations come from my article on the FNZAS website.

If you read the article it tells you everything you need to know about how to work this out for yourself.

Toughened glass has a tensile strength of 175MPa vs worst case 19.3MPa for standard float glass.

All you need to do is change the tensile strength in the calculations and it will tell you glass thickness is required.

For a window 3000mm x 900mm you only need 7.65mm toughened glass to achieve a safety factor of 3.8. On a tank this size I wouldn't consider for a second going below 3.8 safety factor...

The deflection on the glass will be 12.79mm but it will hold. If you took the 19mm panel you were considering and toughened it you would get a safety factor of 23.42 so somewhere in between would be fine.