rimless tank, how much grief would it be?

Discussion in 'General Planted Tank Discussions' started by sks, 28 Jan 2008.

  1. sks

    sks Guest

    Given the attention that rimless/braceless tanks have, just how much grief would it be to build your own? I've talking about something in the order of 6' x 2' x 2' or more.

    1) do you need special glass, or does the glass just have to be extra thick (like twice the thickness?)
    2) how hard is it to make sure you DON'T have excessive silicone around the edges, because that makes the tank look shoddy. I use to make acrylic tanks myself, but stopped since specialist companies are so much better at it, and it's always best to steer clear of dangerous bonding chemicals

    I had a word with my acrylic tank maker today and he tells me the best he can do is American top aquariums, where you basically have a lid as the brace, he doesn't want to do braceless.

    With glass, I'm more worried about moving/transporting the tank since that can be a dangerous affair (one of the reasons I opt for acrylic). But unlike acrylic a glass aquarium can be built on site, so I'm just wondering what's involved and how easy it is to get the kind of finish on the joints that the ADA tanks have.
     
  2. Joecoral

    Joecoral Member

    Messages:
    694
    Location:
    Neath, South Wales
    personally, i'd be worried about the stability of a braceless 6' glass tank...
    im sure someone more knowledgeable will confirm tho
     
  3. ceg4048

    ceg4048 Expert/Global Moderator Staff Member

    Messages:
    8,937
    Location:
    Chicago, USA
    Rimless/braceless 6 foot tanks are no problem if the materials are of high quality but as a DIY project you'd have to be experienced... :wideyed:

    Also you have to plan the canopy properly because there is a lot of bowing at the center of the fore and aft panels.

    Cheers,
     
  4. sks

    sks Guest

    the ADA 6'x2'x2' braceless is 15mm glass. Tom Barr's 6'x2'x2' sapphire glass tank is 19mm. Both use silicone, so the only thing on issue is how clean/tight can I get the seams. I don't think there is anything special about how the tanks are made and there are calculations for sizing the thickness of glass for the rimless tank. I'm sure I CAN DIY it, but I don't know if I can get the perfect seams that ADA tanks has, and that's all really.

    When I use to make acrylic trickle filter components I's use sellotape to mask off the excess cement, when the cement dried you peel it off and removed the sellotape. I don't think I can do this with silicone sealant since it would probably attack the tape being so acidic.

    A 4'x1.5'x1.5' rimless would be no problem out of 10mm glass. The ADA version is 8mm by the way.

    Clive, what do you mean by "canopy"?
     
  5. Garuf

    Garuf Member

    Messages:
    4,959
    Location:
    Leeds.
    I recommend you go with 19mm glass like Mr Barr, he regularly states here there and everywhere that ADA's tanks are made from glass too thin for purpose.
     
  6. sks

    sks Guest

    Tom did not recommend 19mm glass, his tank was made for him by a company he liked, and they probably came up with that thickness.

    If 15mm works for ADA (and these tanks are made in Germany for them, so it's the builder's discretion and not ADA's how thick they want them), then that should be fine. I get the feeling that the ADA tanks use a lower safety margin (which is why thickness came out to 15mm).

    19mm glass is surprisingly heavy, and not something you want to mess about with. I can't build an acrylic tank on site because the chemicals are not available and they are dangerous (just as well the public don't get their hands on it).
     
  7. Garuf

    Garuf Member

    Messages:
    4,959
    Location:
    Leeds.
    That maybe so and I shan't dispute it but I seem to remember Tom saying ada's tanks use glass that's too thin.


    What ever the case I'd love to see how this tank pans out.
     
  8. George Farmer

    George Farmer Founder Staff Member

    Messages:
    7,089
    Location:
    Cambridgeshire
    Tom's latest braceless180cm is 16mm. Doesn't bow at all.
     
  9. sks

    sks Guest

    Not surprise George. If it did bow it would be in serious trouble. :wideyed: Glass tanks are not meant to bow at all since it cannot stand that much bending stress. Thickness is down to how much of a safety factor you allow.

    Since ADA can do it in 15mm, then I can assume it's safe for me to. Although being DIY I might opt for 20mm to allow for slight incompetence on my part since I'm not a professional tank builder and don't have specialised equipment (and I'm sure the German manufacturer of ADA's tank are not in a hurry to give out their bonding techniques to the public!!).

    As a matter of fact I called up a glass supplier and they quoted £180 per metre square in 15mm and £188 per metre square in 20mm. This means a 6'x2'x2' works out to be about £850 for the 20mm glass, which is not too bad considering the ADA tank is about £1300 (which is actually more than my 6' acrylic with american top!!!)
     
  10. ceg4048

    ceg4048 Expert/Global Moderator Staff Member

    Messages:
    8,937
    Location:
    Chicago, USA
    Hi,
    All glass tanks, at least the older designs, bow to some degree on all surfaces. This is a natural consequence of the pressure and the (limited) flexibility of glass. It is for this reason that it is often necessary to place a flexible material under a tank if the tank sits on a flat unyielding surface. If the bottom surface is not allowed to bow, the stresses that cause the bowing will crack the glass.

    Thicker glass simply reduces the amount of bowing. My tank is a rather old design and uses only 12mm glass. There is significant bowing at the top center, perhaps 1cm on each of the long panels, but there is sufficient "slop" and flexibility in the canopy to absorb the displacement. I guess 15mm and thicker reduces this to negligible amounts based on what you guys are saying. 8)

    Cheers,
     
  11. Ray

    Ray Member

    Messages:
    474
    Location:
    Switzerland
    Was your quote float glass or optical quality? If you use float glass watch out for the blue colouration - I believe that the thicker your glass the more noticeable this is. At 20mm it would be twice as noticeable as at 10mm and maybe quite a shock if you are used to acrylic which is superbly clear - a good reason to use consider optical glass?

    If your materials are £850 how much extra would assembly be? I suspect as a % of total cost not so much. I'd be inclined to pay someone to make the tank and indeed deliver and lift onto the stand. With 650L water involved I'd be too nervous about DIY...!
     
  12. sks

    sks Guest

    Clive,

    Of course I know there is bowing. I was speaking from the general public's point of view. All tanks bow to a certain extent but I seriously doubt anyone would care if it's 0.38mm at the centre!! And that's where they factor the safety factor into the calculation. Glass does let you have a bit of "give", but not a lot, and certainly not as much as acrylic. Are you sure you have 1 cm bowing? How long and deep is your tank, because it depends on the ratio, but 1 cm I would not be comfortable with.

    DIYing a 6'x2'x2' tank out of 20mm glass will be a easy, and as long as I get the joints water tight and close, it would be safe since it would be an over specified tank in terms of safety. The only trouble I have with that is getting someone/some people to help me get the glass panes in place, and how to deal with the bonding process so I don't have excessive silicone all over the edges and in tank joints, and that would be the tricky part. I cannot - and will not - have someone make it for me and have to have it delivered into the house, that would literally be a very scary indeed considering the weight we are talking about. Hence building on site is what I'm after.

    Considering all the grief that might be involved I think I better stick to acrylic although I will never get the completely open top that I want, and I suppose the closest I can hope for is a European style top.
     
  13. ceg4048

    ceg4048 Expert/Global Moderator Staff Member

    Messages:
    8,937
    Location:
    Chicago, USA
    Hi,
    Yes, if the glass is thinner than the current convention, like mine is you do care about the give and slop in the canopy. My tank is 6 x 2 x 2 with 12mm glass and at the top center of the front and back panes the displacement is approximately 1 cm. The distortion is clearly visible looking down the end. I calculated the relative distortion by measuring span at top center empty and re-measuring it when full. The difference is roughly 2cm so I assume each panel has equal distortion = 1 cm per panel. The flexibility of glass is truly amazing. While the distortion is visually scary I've learned to be comfortable with it for just shy of a decade.

    Setup day las August:
    [​IMG]

    6 months on:
    [​IMG]

    Isn't science amazing? :eek:

    The tank is really heavy. If you are going to use 20mm glass you had better get Mr. Olympia to help you manhandle those panes. Stock up on ibuprofen as well...

    Cheers,
     
  14. Lisa_Perry75

    Lisa_Perry75 Member

    Messages:
    778
    Location:
    Southampton
    Did you know glass is a super cooled liquid? I was chatting to my fiance who is studying product design with modern materials BSc and apparently most glass is heat treated, which should prevent some glass going. But the elastic limit of glass is low, so I would be concerned about the tank bowing lots in the middle like cegs. He obviously has it right on the limit! Personally I just wouldn't want to risk it.
     
  15. George Farmer

    George Farmer Founder Staff Member

    Messages:
    7,089
    Location:
    Cambridgeshire
    Nice tank, Clive! Bowing or no bowing. :)
     
  16. sks

    sks Guest

    Clive,

    Well, you never know if you don't ask. So each pane is having a 1/90 = slightly more than 1 percent deflection lengthwise, not too bad, although I don't know what the limit is. I doubt they still make tanks like yours now, probably scare people somewhat. You can measure the deflection using a taut string run from the corners end to end. If it was out of acrylic it would bow a whole lot more.

    By the way, nobody uses toughened glass for tanks, reason being that toughened glass falls to tiny pieces when shattered, and that has a dangerous consequence on who it hits.

    So now I know you can get away with 12mm (although I will not try it), I need someone with a 6'x2'x'2 in 15mm to measure his deflection. Or maybe I could go down to Amano's gallery and do it. :D , I'm sure he won't mind. :D
     

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