View Full Version : wood tank size of glass??
dpunk007
10/01/2009, 04:34 PM
hello all,
Im building a wood tank and wondering on the thickness of the glass I should use for the front panel??
the glass would be 141"long and 42" tall..
from the top of the waterline and the bottom of the lowest veiwing point would be 40"..
Any help would be greatly appreciated
uncleof6
10/01/2009, 05:28 PM
hello all,
Im building a wood tank and wondering on the thickness of the glass I should use for the front panel??
the glass would be 141"long and 42" tall..
from the top of the waterline and the bottom of the lowest veiwing point would be 40"..
Any help would be greatly appreciated
After messing with a few different front to back widths for tanks... basing it solely on the length and height of the viewing panel, it looks like 1" glass will deflect ~.5mm with a safety factor of 3.8. Considering it is rather well supported, 7/8" - 3/4" may be fine. But that is a lot of pressure here... so use your best judgment.
Regards,
Jim
dpunk007
10/01/2009, 05:35 PM
It will have a 6" support all the way around the front. plus over lap 2" for sealing area. and I will add 2 cross braces on the top of the tank to help. so really it will only have 3 4ft spans.
dpunk007
10/01/2009, 05:36 PM
I was hoping to get away with 3/4"
uncleof6
10/01/2009, 06:04 PM
I was hoping to get away with 3/4"
As I said, you may get away with 3/4". But it will deflect 1.5mm. 3mm is the point you really need to be biting fingernails, grabbing the bucket worried.... I am not concerned about the tank holding together. It is the glass itself. It is a judgment call. The front glass panel is well supported on the edges. This is figuring on the viewing area only. Figuring for the entire glass panel, the glass would be thicker than 1". And remember I am using figures for a rimmed tank, not a rimless. Also know, that when the glass bows, so will the front support around the glass. So good move on the front to back braces on the top. What I am saying is the calcs take into account the support you will have. The calcs are saying over 1" thick by a couple mm. (27.71mm to be precise.)
So for the entire glass panel (actually a safer calc): 157' x 56" = 45.30mm (1 3/4" glass) and deflection will be .58mm.......this is a rather big tank.... and you don't want to think about how thick the glass would need to be if it was to be rimless.............:eek2:
Yeah I know that don't help much....
Jim
dpunk007
10/01/2009, 06:42 PM
thanks for the info, I will be very helpful
deuce2002
10/01/2009, 06:45 PM
yeah what that guy said lol
dpunk007
10/01/2009, 08:26 PM
Jim,
do you know the safety factor with the 3/4"?
iLLwiLL
10/01/2009, 08:40 PM
As I said, you may get away with 3/4". But it will deflect 1.5mm. 3mm is the point you really need to be biting fingernails, grabbing the bucket worried....
better be a biiiiig bucket if a 1000+ gallon leak springs :D
~Will.
uncleof6
10/01/2009, 09:09 PM
Jim,
do you know the safety factor with the 3/4"?
.46 for the whole panel. 7.81mm deflection. Done.
for 1":
1.19 for the whole panel deflection 3.30mm Done.
The more I think on this, the more inclined I am to go with the whole panel calcs. The reason is, I don't think the plywood will be strong enough on its own to hold the glass against the pressure. You want as little possible deflection as you can get.
All things considered, I would make the tank 140 x XX x 46, but that just might be me, I build glass tanks.
Jim
hey uncleof6 what would you think with a steel cage outside the tank instead of wood for the support. 70x48x48 if it was 1x3 solid Aluminum or 2x2 1/2 inch. what about if you had the glass hardened?
dpunk007
10/02/2009, 04:15 PM
I to was thinking about temperd glass. but if it failed it would shatter leaving over a 1000 gals of water and a lot of fish on the ground. no time to even say OH SH**
uncleof6
10/02/2009, 08:41 PM
hey uncleof6 what would you think with a steel cage outside the tank instead of wood for the support. 70x48x48 if it was 1x3 solid Aluminum or 2x2 1/2 inch. what about if you had the glass hardened?
It is better to use thicker float glass (annealed) rather than tempered, for the exact reason stated above. Tempered is stiffer, but more brittle. Don't take as much to break it if ya knock it with yer head.......with float glass you will probably say ouch instead of OH S***.
As for your dimensions, with rim: 29.95mm. (1 1/8") glass. There are some that say that the length is not significant, however that is not quite accurate.
Regards,
Jim
dpunk007
10/02/2009, 09:36 PM
just measured the viewing area (window)
so this is exact
37.75"x132"
add the 2" overlap would be
41.75" x 136" (size of glass sheet)
and the waterline will be 1in over the viewing window so that would be 38.75" deep.
So is 3/4 out of the question? not trying to be cheap just would be hard to get glass that thick and then manage to handle it with out killing myself.
found a tank in the large reef tank section that is 15foot x 5.5 foot x 35.4 inches.
3/4 all sides 1" on bottom?
uncleof6
10/03/2009, 01:13 AM
just measured the viewing area (window)
so this is exact
37.75"x132"
add the 2" overlap would be
41.75" x 136" (size of glass sheet)
and the waterline will be 1in over the viewing window so that would be 38.75" deep.
So is 3/4 out of the question? not trying to be cheap just would be hard to get glass that thick and then manage to handle it with out killing myself.
found a tank in the large reef tank section that is 15foot x 5.5 foot x 35.4 inches.
3/4 all sides 1" on bottom?
The large reef tank section tank calls for 23.07mm sides, and a 30.41 bottom glass
Yours is still calling for 29.95mm glass. These figures are for a safe tank-- And that is provided the support for it is adequate. I am not saying: hey if you don't use 1" glass, (actually just a little more) your front panel is going to blow out. I am just relating what a safety factor of 3.8 (considered the minimum) calls for. I use a safety factor of 7.6 for rimless tanks, so I am not over fudging the numbers.
I hear you about the weight, I can't lift these glass panels I find myself faced with, and expect to walk away either. That really is the only advantage I see to using acrylic (that is an opinion.)
Regards,
Jim
dpunk007
10/03/2009, 06:30 AM
wouldn't mind using acrylic but every one says it is impossible to get a good seal. does the thickness requirements change between glass and acrylic?
salty joe
10/03/2009, 07:22 AM
[QUOTE=uncleof6;15786833]As I said, you may get away with 3/4". But it will deflect 1.5mm.
If the glass was supported on all four sides and all four sides were rock solid with virtually no deflection, would this 3/4" glass bow out in the center by 1.5mm? If so, would this movement by the glass tend to cause seal failure since the supporting sides remain motionless?
Can you brifly explain the safety factor?
chriscobb
10/09/2009, 09:55 PM
With building a plywood tank you don't want the glass panel resting on any wood.....it should be free floating per say, and a very good place to get info is fingerlakesreef....they have a dedicated section just for plywood tanks...
As far as using acrylic instead of glass. That is definitely an option.....You can get a perfectly good seal with acrylic. The adhesive you would need to use with the acrylic and plywood build would be Dow Corning 795. I'm going to use acrylic for my "woody" build.
uncleof6
10/09/2009, 10:58 PM
[QUOTE=uncleof6;15786833]As I said, you may get away with 3/4". But it will deflect 1.5mm.
If the glass was supported on all four sides and all four sides were rock solid with virtually no deflection, would this 3/4" glass bow out in the center by 1.5mm? If so, would this movement by the glass tend to cause seal failure since the supporting sides remain motionless?
Can you brifly explain the safety factor?
Deflection of the glass can cause seal failure. I do not design, or build, plywood tanks. I am looking strictly at the glass itself. Glass is not elastic per se, so it would not bulge as acrylic would in some circumstances (and does-- I have seen many pot bellied acrylic tanks)
I am not going to spend hours going through the information that chriscob pointed towards, however the idea of "floating" I would assume to mean that the glass is held in place by silicone on both sides, and in this case the glass would deflect independently from the wood, to a point.
The safety factor is a ratio between the breaking stress of a structure or member, to the estimated load (or stress) on the structure or member in actual use. It is used in all good engineering design, and is not optional. It takes into account variations in material properties, fabrication and construction tolerances and such. It eliminates the OH Sh** I should have used thicker glass factor.
In the context of glass aquariums it is used to determine the allowable bending stress on the glass panel with the formula: Tensile Strength of glass/Safety Factor.
Regards,
Jim
chriscobb
10/10/2009, 10:36 AM
If you reference AcroSteve's build and look and search over on Fingerlakesreef dot com you'll fully understand why with experience with these type of tank builds why you don't want the glass resting or nestled in some sort of frame....With the plywood build a silicone bead is laid and the glass or acrylic is laid and when the tank is filled with water the outward pressure of the water on the glass or acrylic is creating the seal....
dpunk007
10/10/2009, 02:38 PM
thanks for the info guys,
Chris were do you get Dow Corning 795? looks like I will have to go with acrylic. Glass this thick is 150$ per sq ft.
uncleof6
10/10/2009, 03:36 PM
just measured the viewing area (window)
so this is exact
37.75"x132"
add the 2" overlap would be
41.75" x 136" (size of glass sheet)
and the waterline will be 1in over the viewing window so that would be 38.75" deep.
So is 3/4 out of the question? not trying to be cheap just would be hard to get glass that thick and then manage to handle it with out killing myself.
found a tank in the large reef tank section that is 15foot x 5.5 foot x 35.4 inches.
3/4 all sides 1" on bottom?
The behavior of an all glass tank panel, cannot be used to predict the behavior of a glass panel, when the water level is above the top edge of the panel, and below it.
In an all glass tank, the pressure at the water level of the panel is zero, and increases proportional to depth, with a maximum at the bottom of the panel equal to the pressure on the bottom of the tank. At any given point in the water column, pressure will be equal in all directions. So at the middle of the water column, the pressure will be half the pressure at the bottom of the tank.
So starting 1" below the water level at any given point on the glass panel , (vertically speaking) the pressure will be greater, than it would be in an all glass tank. of the same dimension as the viewing panel, with the water level 1" below the top edge of the glass. There will also be water pressure on the area surrounding the glass panel against the fiberglass/plywood, which will probably deflect also.
Put on top of this, the two dissimilar materials in use, and the deflection being different for each material, and the model becomes useless really.
The model I use does not account for this, so it is an estimate-- even more so in these cases.
The safest thing to do is look at plywood tanks of similar size, that have been up and running long term, and look at the glass thickness, and the construction techniques used.
I am getting batty or sumptin, I already answered this, however this is a better answer for ya anyway.
Regards,
Jim
chriscobb
10/10/2009, 05:09 PM
I have to do alittle digging around in my paperwork, but I know I have the number saved on my cell phone....It's a place in North Carolina that I found carries it, and the price isn't bad....let me do alittle digging and I'll get you the info...
chriscobb
10/10/2009, 05:17 PM
Conceal is the name of the company based in North Carolina...their number is 610-532-5391. It is a construction grade adhesive, and is safe for the use....Acrylic(James) also gave me the tip on the adhesive as well.....I got the number from my acrylic supplier...
dpunk007
10/10/2009, 09:42 PM
thanks again
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