brozi Posted January 25, 2009 Report Share Posted January 25, 2009 Just wondering if anyone can clarify something for me, It's about glass thickness so bear with me please! If your are using toughened glass instead of plate glass do you have to use the same thickness or because toughened glass is so much stronger(approx 5 times so I'm told) does it stand that you can use a thinner glass, eg if the calculator tells you that you need 15mm thick glass (I'm presuming thats plate/annealed glass) would 10mm thick toughened glass be acceptable? Thanks Quote Link to comment Share on other sites More sharing options...
TM Posted January 25, 2009 Report Share Posted January 25, 2009 Warren or Barrie may be able to help on this one. But yes if it is toughened then you can use thiner glass. How you work this out ??? Quote Link to comment Share on other sites More sharing options...
brozi Posted January 25, 2009 Author Report Share Posted January 25, 2009 Thanks TM, Will they read this thread or do I contact them elsewhere? Thanks for your help. Quote Link to comment Share on other sites More sharing options...
Barrie Posted January 25, 2009 Report Share Posted January 25, 2009 from a strength point of view you can use thinner glass however the glass will bend more and cause a breakdown of the seal... silicone Your advisor is correct in telling you that toughened glass is 5 time the strenght of annealed (not toughened)glass. The weak point of toughened glass is the edges. Simply put, glass is toughened by shrinking the outside surfaces and placing in inside under pressure. This creates strength which is sitting there waiting to be released when the edges get damaged. On some toughened glass you may well have noticed damage to the edge...may not be broken but it can break at any stage. Stick with the thickness recomended. Both Warrens calculator and the glass merchants calculations are similar. I tend to go overboard as I have seen far too many disasters. DONT CUT CORNERS please Quote Link to comment Share on other sites More sharing options...
livingart Posted January 25, 2009 Report Share Posted January 25, 2009 DONT CUT CORNERS please or you might CUT OTHER THINGS Quote Link to comment Share on other sites More sharing options...
brozi Posted January 25, 2009 Author Report Share Posted January 25, 2009 Thanks for the advice people much appreciated I certainly don't want a failure. Cheers Quote Link to comment Share on other sites More sharing options...
Warren Posted January 25, 2009 Report Share Posted January 25, 2009 If you're going to use toughened glass, as Barrie says, it will need to be perfect. Get the edges ground prior to it being toughened and make sure there's no damage before using it. If you want to use toughened glass, just substitute the tensile strength for toughened glass into the thickness calculator. Standard float glass has a tensile strength of 19.3 to 28.4 MPa (so use 19.2 for calcs) and toughened glass 175MPa (so use 174). Toughened glass costs about twice as much as the same thickness annealed glass. If it breaks, it will all fail by shattering completely where annealing glass often just splits and leaks. At least with annealed glass you usually have some time to rescue the tank as it leaks out... On my new tank I am going to use 15mm low-iron toughened glass. This will give a safety factor of approx 22! Quote Link to comment Share on other sites More sharing options...
Barrie Posted January 25, 2009 Report Share Posted January 25, 2009 Warren Do you think that low ion will make any noticeable difference? I did an experiment (useing eyes only) and found that out of 8 people, none could tell the difference but it was only 6mm Quote Link to comment Share on other sites More sharing options...
Warren Posted January 25, 2009 Report Share Posted January 25, 2009 At 10mm+ there is a noticeable difference and at 15mm+ a lot of difference. Many of the marine aquarium keepers won't use standard glass as it effects the viewed colour of the reef and water looks less sparkly. Low-iron glass is pretty much crystal clear - no green tinge. There's also less than 2% tensile strength difference. I think the iron just makes it easier to work with when it's being made. At approx 10% extra cost my personal preference is low-iron when used on medium sized tanks of 600 - 1400L. Quote Link to comment Share on other sites More sharing options...
Barrie Posted January 25, 2009 Report Share Posted January 25, 2009 at the retail level there is over $100 per meter difference so they must have quite afew offcuts around? Quote Link to comment Share on other sites More sharing options...
Warren Posted January 25, 2009 Report Share Posted January 25, 2009 Hmm, my local glass merchant's quote was only 10% higher for low-iron. Maybe they made a mistake. Quote Link to comment Share on other sites More sharing options...
Barrie Posted January 25, 2009 Report Share Posted January 25, 2009 I will check it out at work tomorrow and let you know as Im sure he has made a mistake Quote Link to comment Share on other sites More sharing options...
brozi Posted January 26, 2009 Author Report Share Posted January 26, 2009 Once again I have to say thanks very much and that this advice is greatly appreciated! I'll go have a yarn to our local glazier here because if I go to the toughened glass way you obviously have to ask for the edges to get ground specially going by your post Warren. I'll keep you informed as I progress. Quote Link to comment Share on other sites More sharing options...
Warren Posted January 26, 2009 Report Share Posted January 26, 2009 You don't have to grind the edges - it's just tidier and easier to see if the edge is damaged. It adds a small extra cost but makes the finish very good. It also make the silicone join very uniform and it can be a bit thinner than normal as well due to no uneven edge to worry about high points. It's also advisable to go with ground edges as the glass gets thicker, probably above 10mm as the unevenness gets worse as the glass gets thicker. This is compounded by thicker glass being used on larger tanks that are typically longer and taller, putting more stress on the edges and silicone joints. Any movement in the silicone reduces the tolerance to a high point in one panel touching another panel and causing high stress area and possiblea breakage. Ground edges go a long way to stopping or significantly reducing this problem. Thinner silicone joins flex less and are stronger. Quote Link to comment Share on other sites More sharing options...
brozi Posted January 27, 2009 Author Report Share Posted January 27, 2009 Warren I have substituted the two fiqures Re annealed/toughened and going by my calculations I've gone from needing 14mm annealed to 5.5mm toughened from which I'd look at going either 8 or 10mm. Does this sound right to you (tank height = 950mm, length 730mm) Quote Link to comment Share on other sites More sharing options...
TM Posted January 27, 2009 Report Share Posted January 27, 2009 The flex in the glass should still be the same so good bracing is really important. I made a tank a month or so back that was 900h x 600w x 290d. Was to go in a wall hence the random size. I used 12mm toughened with polished edges, at each end the was a 24mm contact/join. A strip of 12mm polished about 50mm wide top to bottom. No flex at all. With not looking at figures and going on what i have done in the past, i would look at 10mm to be the min thickness you would want even if as you said the workings say you could get away with thinner. 12mm may be better. Quote Link to comment Share on other sites More sharing options...
TM Posted January 27, 2009 Report Share Posted January 27, 2009 The flex in the glass should still be the same so good bracing is really important. I made a tank a month or so back that was 900h x 600w x 290d. Was to go in a wall hence the random size. I used 12mm toughened with polished edges, at each end the was a 24mm contact/join. A strip of 12mm polished about 50mm wide top to bottom. No flex at all. With not looking at figures and going on what i have done in the past, i would look at 10mm to be the min thickness you would want even if as you said the workings say you could get away with thinner. Quote Link to comment Share on other sites More sharing options...
Warren Posted January 28, 2009 Report Share Posted January 28, 2009 Yeah, my gut says 5.5mm is too thin as well even though the calcs say it's ok. As TM says, 12mm is a good size and would recommend this too. Quote Link to comment Share on other sites More sharing options...
Barrie Posted January 28, 2009 Report Share Posted January 28, 2009 no such glass now days as 5.5 ite either 5 or 6 (8,10,12,15 and 19) Quote Link to comment Share on other sites More sharing options...
Warren Posted January 28, 2009 Report Share Posted January 28, 2009 Yeah, I know - but the thickness calculator doesn't know the glass thicknesses available, it just tells the exact thickness required based on the safety factor. The designer will always have to chose the next size up from what is locally available. Quote Link to comment Share on other sites More sharing options...
brozi Posted January 28, 2009 Author Report Share Posted January 28, 2009 Whew its good to know I worked that calculation out all right. As with you guys my gut was telling me the 5.5mm was too thin (I was aware that glass didn't come in this thickness) and was hedging toward the 10mm myself even though it's going to be a very narrow in wall tank which is fully supported on both sides and back with full access from the top but I'll have another rethink on the 12mm. Ps TM I'm a bit confused about this 24mm join - that 50mm strip - am I right in thinking thats it's running down the side or am I completely wrong? Cheers Quote Link to comment Share on other sites More sharing options...
TM Posted January 28, 2009 Report Share Posted January 28, 2009 Ps TM I'm a bit confused about this 24mm join - that 50mm strip - am I right in thinking thats it's running down the side or am I completely wrong? Cheers Yeah so the 50mm face is glued to the end and the 12mm face is glued to the front. When you look at it from the front the width of the glass would be 24mm. I do this on each corner and the base. I also do a similar thing along the top of the centre brace of the larger tanks. As mentioned prior if there is a small amount of flex this puts alot of pressure on the joins. My tanks tend to be over built but would rather do that than have them blow. Quote Link to comment Share on other sites More sharing options...
brozi Posted January 28, 2009 Author Report Share Posted January 28, 2009 Thanks for the clarification TM. I also think erring on the side of caution to be a wise course of action. Quote Link to comment Share on other sites More sharing options...
livingart Posted January 28, 2009 Report Share Posted January 28, 2009 one who errs on the side of caution has erred in the right direction Quote Link to comment Share on other sites More sharing options...
TM Posted January 28, 2009 Report Share Posted January 28, 2009 right, so now you have the info when will the build start. Warren, are you onto yours yet? Quote Link to comment Share on other sites More sharing options...
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