Tank Alterations

Discussion in 'General Discussions and Advice' started by scubaninja, 3 Jun 2009.

  1. scubaninja

    scubaninja

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    Hi Hennie
    Just a couple of questions on tank strength. My tank has the dimensions of 2000X700(water height)X700. It has 10mm glass all round with euro bracing on top from side to side on the front and back(10mm glass, width 100mm) but not on either side of the tank. It then has 2 braces running from the front to the back at a third and two thirds from the left. 10mm glass with the width being 200mm each this time. What i would like to know is if its possible to have a wave maker on this tank without it collapsing or seals breaking etc. I think i remember the need for the side panes to be double the thickness but i'm not sure. I wanted to know your thoughts on this and if i could somehow work out what i need to do to make it strong enough and if it would be a viable option, as i may be moving in a while so the tank will be coming down and changes can be made when it can sit empty for a while.

    Is there any extra bracing i can do to avoid having to change the side panels altogether?
     
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  3. viper357

    viper357 Admin MASA Contributor

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    That's odd, the last time I measured it was 750 front to back :whistling:
     
  4. scubaninja

    scubaninja Thread Starter

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    yeah you measured wrong:) its 750 high and 700 wide:)
    Posted via Mobile Device
     
  5. Hill

    Hill

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    He was probably lying on his back when he measured......:1:
     
  6. shane

    shane

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    :lol:
     
  7. mayoginn

    mayoginn

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    Why not try having a metal frame around the corners of the tank, angle iron should be strong, can even paint it your favourite color :p
     
  8. scubaninja

    scubaninja Thread Starter

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    not a chance. thanks mayo but i'm gonna wait for Hennie on this
     
  9. mayoginn

    mayoginn

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    No problem, lucky Marines is my hobby and not my line of work :D
     
  10. Reef Maniac

    Reef Maniac MASA Contributor

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    Use of the glass thickness calculator shows that the safety factor of the side panes is only 1.7, which is pretty low. The calculator does not take side bracing into account, though, and with the bracing you described it is obviously strong enough for "normal" use.

    Difficult... With such a low safety factor I would not risk the added stres imposed by a wave maker without some serious bracing. The problem is, though, that the waves generated in an empty tank, and that in a tank partially filled with rock, will be totally different - and depending on the rock-scaping you could have vastly differing stress points by just changing some of the rocks. It will be very difficult to actually predict the effect of the wave surges through the tank, and even more so to predict the effect of any harmonics generated by the regular wave pattern, and which could be more severe than the actual wave.

    Personally I would not risk this, but if you really want to, you should look at doubling the Euro-bracing right around the perimeter, both top AND bottom of the tank, and if possible also re-inforce the actual silicone joints, perhaps by 50mm - 75mm wide strips of glass being siliconed over the outside of the vertical joints

    I suppose it's as Dirty Harry said: "How lucky do you feel..."

    Hennie
     
  11. scubaninja

    scubaninja Thread Starter

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    Yeah i saw that in the calculator and was a bit shocked myself when it was so low, thank goodness for the bracing:thumbup:

    Well this would be a big job to do and i wouldnt just fumble about on my own, i would enlist the help of someone who really knows how to build tanks cause i wouldnt stand within ten metres of one of my own creations:p

    Ok, so as far as bracing goes it would mean absolute havoc as there would be bits of glass absolutely everwhere, so that puts me off that idea. Now if i were to pull the tank apart, take off all the old silicon etc, and in stead put a thicker glass on the ends, say for example, 20mm panes, and re did the bracing so it was purely euro bracing all around, 100mm all around? possibly double layers? Do you think it would be sufficient? I have seen a bit of silicon flaking in the outside of one join, would this mean i should re-silicon everything anyway? The overflow is a bit pathetic aswell and this time would give me a chance to correct a lot of things in my view

    I would really love to have the side to side motion and be able to remove all but some of my pumps in the tank but if the job is more trouble than its worth i will just move on to new ideas

    thankyou for taking the time to respond to my questions?
    haha got vipers magnum in the memory already:p
     
  12. scubaninja

    scubaninja Thread Starter

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    Bump

    Hennie how much do you think bracing plays in a tanks construction? Trying to weigh my options and it seems i might have to downsize, and with what sizes i can work with if i use 10mm glass it gives me a safety factor of 3.6. How much would full eurobracing, top and bottom increase this safety rating?
     
  13. Reef Maniac

    Reef Maniac MASA Contributor

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    That would certainly help, but I'm afraid that any wave propagating down the length of a tank will exert pressure in all directions, and will thus be pushing against the glass of the long sides as well - think of it as a "bulge" moving through the water. The glass with the longest span (i.e. the front and back panes) will have the largest deflection, and it is this excess deflection that can cause the glass to crack.

    The Euro-bracing acts as a beam, thus resisting deflection. Although I don't have any hard facts, I believe that one can drop one size (i.e. 12mm to 10mm) glass thickness if the bracing is done properly, on both the top AND bottom (on the inside) of the tank. To be done "properly", one would need the bracing to be wide enough to be able to work as a beam, and thick enough to be able to withstand deflection of it's own.

    I would never personally recommend skimping on glass thickness, or relying on the bracing to keep the tank safe, but IF I had to do this I would make the bracing at least 100mm wide, and 12mm thick (or perhaps 2 x 10mm panes siliconed together...).

    The silicone joints are, of course, just as important as the glass, and must be done correctly, especially in a tank exposed to constant surges. Silicone needs a minimum amount of "body" (thickness) between the glass panes to achieve full strength. From what I've read, the general recommendation is to have a layer of silicone (after it has set) of at least the thickness of a match stick between any two pieces of glass. This should go a long way in absorbing the force of the water, as the glass panes would "flex" at the silicone joints, rather than in the glass itself.

    Having said all this, I would still urge you to rather build a new tank using at least 12mm glass AND proper Euro-bracing for your "surge" tank - if nothing else, you will sleep much better at nights :whistling:

    Hennie
     
  14. riyadhessa

    riyadhessa

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    So to just butt in...
    So Hennie what thickness glass would you recommend for 2meter long-900wide-750height...
     
  15. Reef Maniac

    Reef Maniac MASA Contributor

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    As per the glass thickness calculator:

    Assuming the water level to be at 720mm: Side panes = 16mm, bottom pane = 20mm.

    You can keep the bottom pane at 16mm IF the tank will be standing on a rigid (concrete) slab, which will support the bottom glass over it's full area.

    Hennie
     
  16. riyadhessa

    riyadhessa

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    Thanks for your swift reply
     
  17. scubaninja

    scubaninja Thread Starter

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    Ya sleeping soundly at night would be a great help:whistling: Do you mean that i must go 12mm on the tank where the safety factor is 3.6? I was planning on doing a little 4 ft on the side but if i need to downsize on the move and sell the 2m then i would want to do the tank properly so i rethought that initial idea. The tank would be 1200X600X600 and with the 10mm glass it has the safety factor of 3.8 if the water height is 550 or so. What do you expect the price difference between using 10mm and 12mm would be? will it be a large jump? If i am to do this tank i will do it properly and would preferably opt to go for the 12mm giving me a safety factor of 5.2 without bracing where it may then take me longer to get the tank up an running instead of my tank exploding when i tried to save some bucks. As far as the surge goes, i understand that the wave willl vary greatly even by moving a couple of rocks, but do you think it the wave could be a strong enough flow for SPS? Its my understanding that waves in a larger tank may move faster hence being a 'greater' flow suitable for SPS but would i be able to achieve the same in a smaller tank keeping in mind that my tank would hopefully be strong enough? Would the stress on the glass be worse if there is no rocks or more? so if i were to build the tank and then test it outside where it braking will not cause damage to the house or anything? I say that for peace of mind really, cause if a surge with no rocks is stronger and the tank can withstand it perfectly fine then it would be peace of mind for when it has rocks in it etc.
     
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