Engineers and experts needed:) normal vs toughened glass

[henward]

OK,

say a tank requires 25mm glass, if i use 19mm 'toughened' glass, will that handle the pressure?

or is toughened only the surface and scratches or is it actually harder, stronger and tougher and able to handle more pressure?

[hovmoller]

Perhaps :smot: but:

Even if it is stronger what would be the point?

Surely toughened would be quite expensive as you would need to order new glass made to size

[David R]

You'd have to order "new" glass with it being that thick as it can't be cut using the usual 'score and snap' method, needs to have the edges machined etc. And there aren't likely to be any offcuts big enough for the kind of tank Henward is likely to be planning using 25mm glass....

[ilwis]

OK,

say a tank requires 25mm glass, if i use 19mm 'toughened' glass, will that handle the pressure?

or is toughened only the surface and scratches or is it actually harder, stronger and tougher and able to handle more pressure?

not recomended

from what i understand you need to use pane glass (window glass)

toughened glass when it breaks shatteres and therefore if you "bump" the tank you get ALL your water on the floor in a rush wheres window glass will crack and give you a slow leak (better to save the fish than picking them out of glass infested water on the floor)

also toughened glass is "stiffened" so is less resilent to strain (pressure)

there are other reasons but i cant remember them off the top of my head

also 25 mm glass! OMG how big is the tank! for that much water i would stay away from toughened glass because the flexibility required by the pressure will pop the toughened glass like a balloon over the standard plate glass better to look into perspex for that size tank you can get up to 98% clarity with perspex wheres glass is lower i think 80% off the top of my head

[ilwis]

also might want to check this out

http://www.theaquatools.com/building-your-aquarium

[calculator]

Glass is toughened by cooling the outside faster then the inside, which due to the way glass is formed causes there to be stored stress in the glass. When breaking the glass this stored stress has to be over come before you break the glass, giving it extra 'toughness'. (Glass can also be 'over toughened' where the stored stress is to high, and can the be cause to shatter by little things like change in temperature, but that is irrelevant to your question).

To answer your question It might be enough, but it depends on how much it has been toughened, and how much redundancy you want in the strength of the glass.

Also sort of unrelated toughened glass shatters differently to untoughened, as it will hatter into small pieces instead of the cracks you see when untoughened glass breaks.

[henward]

I have already encountered a problem.

19mm glass is thickest you can get in nz!

so.... my 25mm is really, impossible.

i was thinking 2.4m x 1.2 x 1.2

ply diy build.

but i think david is right, might have to cut it down to 90cm high. the rest of the dimensions can stay the same, even 3 metres is fine in length.

that can have 19mm glass safely.

i considered acrylic, but i would need roughly double the thickness of acrylic as to glass... (25mm glass, 40mm acrylic) and acrylic scratches easily with plecos.

i asked the acrylic guys if i can use anything, they sid a 3M coating used for security is good, but not sur eif that can be submerged.

I think i will have to redo my sizes.

[henward]

depends on the size of the house i get and the lay out.

but that calculator says

3m by 1.2m wide by 90cm high

2.5 safety factor at 19mm glass.

What do you think?

2.5 safety factor is good right?

if i rewduce the height to 85cm, then the safety is 3.

is that much different.

I weant the ACTUAL water height to be either 85 cms or 90.

does that calculator take into account the height of water lost due to the glass or is it actual height of water?

cos you always lose a few cms with glass thickness and stuff.

OR should i let that few cm get lost so gives me extra safety?

[Ira]

i asked the acrylic guys if i can use anything, they sid a 3M coating used for security is good, but not sur eif that can be submerged.

I think i will have to redo my sizes.

If you're worried about scratching on the inside why not put a thin, non load bearing pane of glass on the inside against the acrylic?

[henward]

If you're worried about scratching on the inside why not put a thin, non load bearing pane of glass on the inside against the acrylic?

considered that.

but to glue that on - you would need perfectly clear glue, no bubbles... whcih is almost impossible

if you lightly silicone the sides, you would get air in the middle

that would condense the air in there... it would need to be an absolute vacuum.

so... stuck again!

but, in saying that, i think going for the 3m x 1.2 x 90cm is the best optin, its still very high, 3000 litres.... i would just need to put it on a very short 'stand' to make it eye level for when you sit on a lazy boy... (i have 2 set to go in front of the tank)

thats why i wanted 1.2 high.

but 90 is fine, i just have to make up the 30 cms up and build from that.

but the safety factor?

any comment?

2.5 to 3?

[Ira]

I'd say 2.5 should be heaps. More than most tanks anyway. And a tank that size even if someone comes walking up and starts banging on it and hitting it intentionally that's going to be a relatively small force.

[henward]

I'd say 2.5 should be heaps. More than most tanks anyway. And a tank that size even if someone comes walking up and starts banging on it and hitting it intentionally that's going to be a relatively small force.

thought so

i mean the structure is ply. only the fornt is glass.

cos its ply, the glass wont be completely exposed from the edge, there will be a 'rim' at the front so the front wont be 3m x 90cm in terms of exposed glass.

though i will prob just get glass that size and put ot on the entire front of the structure.

[ilwis]

i think ira's idea of the thin not loadbearing pane is worth looking into its only to stop the main pannel from getting scratched so it doesnt need vacume it doesnt even need to be sealed if its just sitting in the water and heald bith a blob of silicone (or im expecting you want to use rubber glue) a blob on that in the top cornors of the glass so water can run all around it you wont have any of those problems mentioned before what might be better tho is if you make a track with the glass to slide in eaisly you can then clean in behind it it would make it allowable to use 3mm glass to protect it

also from what i understand the safty factor means if you have a safty factor of 2.5 the tank can handle 2.5x the ammount of pressure the glass is rated to handle (to allow for defects in the glass) there already is a safety factor the manafucturs place on the glass but tank builders add in this extra safety factor

[David R]

If you're worried about scratching on the inside why not put a thin, non load bearing pane of glass on the inside against the acrylic?

Acrylic will flex more than glass, so you would have to use very thick acrylic to avoid having any deflection otherwise the glass would end up taking the weight, or have the glass sitting off the acrylic which could lead to problems with cleaning. Is be reluctant to have a piece of thin glass in a tank with a 50cm aro too.

Henward, one of the big advantages with a timber framed tank is that the wood is completely supporting the glass, and the silicone is just there to seal it, not structural. I think 19mm would be fine for a 900 mm high timber framed tank, and can think of at least one example that has been running for years.

[ilwis]

Henward, one of the big advantages with a timber framed tank is that the wood is completely supporting the glass, and the silicone is just there to seal it, not structural. I think 19mm would be fine for a 900 mm high timber framed tank, and can think of at least one example that has been running for years.

i agree with ira if you frame the glass with wood and put a heavy wood framing the top of the glass like remu (i know you prob wont use rumu it was just a heavy wood i thought of right away) the wood will hold the deflection down and it wont be structural so i dont see any reason why it wont work

also if your worries you can always but use angle iron for framing and then split the glass down the middle weild 2 bits of angle iron together like a T and fit the glass to give it that extra brace in the middle it would prob surport a safety factor of 4 then, but that is just my own speculation

i guess you could use wood for the centre brace but if you were going to do that you would have to route the t shape you cant just nale or screw 2 bits of wood together.. too much pressure (tank that size even with heavy ply for other sides need to think carefully about your joins)

[henward]

yeah, if acrylic flexes, before you know it the glass on it will break.

so no go there.

I think i have to rationalise my expectation and go for a 90cm high tank.

19mm is fine.

3000 litres is still a good aro comm size.

there are many plans on mfk, its basically a tub you are building and sealing the inside with resin or expoxy pond sealer stuff.

now, where to buy that... is another question lol

[livingart]

resin is available on TM all the time

you will need at least 4 litres and woven matting as well

[ilwis]

yeah, if acrylic flexes, before you know it the glass on it will break.

so no go there.

I think i have to rationalise my expectation and go for a 90cm high tank.

19mm is fine.

3000 litres is still a good aro comm size.

there are many plans on mfk, its basically a tub you are building and sealing the inside with resin or expoxy pond sealer stuff.

now, where to buy that... is another question lol

you can get the liquid rubber from mitre 10 mega its $180 for a large tin its in the paint section tho they dont call it liquid rubber in nz i think its gasonal or some weird name begging with G its totally water proof and inert. also a good place to look for resin eg fibreglass is boating places have some fearly cheap if your in the north shore there is a boat place by the roundabout by supercheap albany i got some from there when i had to fix a pool it was much cheaper than anywhere else but that was 5 years ago and i dont know if its inert or not

i havent looked into pond sealer... im kinda intrigued with what there is

[livingart]

this is the stuff i used on 3,000ltr

http://www.trademe.co.nz/motors/boats-m ... 815843.htm

[henward]

Do you have to use the woven stuff

or is it like a paint you put on?

It would be much easier to get something you just pour or paint on a fiew layers as opposed to a fibre glass type thing that you have to put woven stuff on to.

[livingart]

no you don't but it adds strength to it

i used 15mm ply then 1 coatof resin allowed to soak in, then mesh and 2 more coats

any rocks can chip coat if handled roughly

[David R]

Do you have to use the woven stuff

or is it like a paint you put on?

It would be much easier to get something you just pour or paint on a fiew layers as opposed to a fibre glass type thing that you have to put woven stuff on to.

It depends if you want it just for the waterproofing or also for structural strength. Personally I think a good application of fibreglass is a better option than the liquid rubber type products, and as I understand the silicone seals better to fibreglass too.

You're a bad influence, I thought I had made up my mind about doing an all glass tank!!

[henward]

It depends if you want it just for the waterproofing or also for structural strength. Personally I think a good application of fibreglass is a better option than the liquid rubber type products, and as I understand the silicone seals better to fibreglass too.

You're a bad influence, I thought I had made up my mind about doing an all glass tank!!

haha

well, actually, i think it will be reall fun to build one!

i am not a handy man but father in law is quite into this.

so reckon it would be a cool project.

I am considering a inbuilt filtration system, hidden at the back or side.

OR a rack for the sump on the side... See how it goes. so its tidy.

If the house allows for sump to be outside, id do that. way easier.

but depends on the house i suppose.

but the ply tank is appealing, at that size, it may be more cost effective.

[henward]

I am thinking how i would do an overflow on tis ply tank?

do a standard over flow as if it was glass?

OR a hole on the wall, with a drain? but suction on that will be quite massive ? danger to fish?

[ilwis]

I am thinking how i would do an overflow on tis ply tank?

do a standard over flow as if it was glass?

OR a hole on the wall, with a drain? but suction on that will be quite massive ? danger to fish?

have you considered having a long pvc pipe the length of the tank with alot of holes in it to distrubite the suction over the tank?

also if you made the tank what would stop you from using the plywood to make the sump also? it would help better than the glass to keep the heat in the tank especally if its outside?

also something of note as a cheaper way of the sump why dont people just use a plastic tub? its not like your ment to see the sump anyway