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"Harry Krause" wrote in message
news:1101825017.A8YvNxGot0vzl0lmZX6wyQ@teranews...
dixon wrote:
I wanted to build a 1000 plus gallon aquarium in the new house I was
having
built. I wasn't sure how thick to make the front glass. The rest of the
tank
would be fiberglass covered steel. The dimensions I arrived at were 8
ft.
across, 6 ft. front to back and 38 in. tall. This would be 1137 gallons.
A
friend had a tank that was 38 in. tall but only 18 in. front to back. It
was
also 8 ft. long. (284 gallons). The glass in his tank was 3/4 in thick.
My
tank would be identical except the front to back dim. would be 72 in.
At first I was concerned that there would more pressure on the front
glass.
After much research I became confident there would be no difference
regardless of front to back depth. For simplicity lets call depth the
front
to back dim. and height the top to bottom dim. I found charts that told
the
pressure at every height of water in inch increments. To figure the
total
"push" on the front glass, you just need to find the pressure at the
halfway
point(19 inches in this case) and multiply by the total sq. in. of the
glass
(3,648). I believe
at 19" the pressure was about .686 or so psi. It figured out to be
around
2,500 lbs. of force on the glass. It would be about 9,480 lbs of water.
As
I
was filling the tank, a straight edge laid against the front glass
showed
the glass bowing outward very noticeably even at 1/4 full. I nervously
filled it full. Now it was very bowed even to the naked eye. The 2,500
lbs
was definitely there on the glass. Now, try to visualize the front glass
as
a giant rectangle piston with 2,500 lbs of force on the inside. If you
put a
4"x4" in the center of the glass that ran across the room to an opposite
wall and put a bathroom scale (quite a scale!) against the wall or
better
yet, an "I" beam, the scale after filling, would read a total of 2500
lbs.
Or 25 men each pushing on the outside at 100 lbs would cancel the
pressure
on the glass. Now, here's where the troubling part comes in. Lets say
the
back of the tank, instead of being 72" away from the front is moved
forward
until it is just 1/8 of an inch away from the front glass. Now there is
less
than two gallons of water in the tank. I have trouble seeing the glass
(3/4
in. thick) bowing from 2,500 lbs of "push" from less than two gallons of
water(16 lbs). I suppose we could even shrink the 1/8 in. to a few
thousandths and put a thimble of water in. Would there still be 2,500
lbs
of outward force from a gram or two of water? Would the heavy duty scale
across the room be forced all the way to the two thousand, five hundred
pound mark?

Dixon




If you really want some help with this, I suggest that rather than
depend upon wild-assed, theoretical guesses from the readers of this
newsgroup, you consult with some of the real experts who build
commercial display aquariums. That's some floorload by the way...hope
that tank is sitting on a concrete floor.

Thanks for the advice Harry. Actually the tank has been full for 14 yrs.
now. When building the house I poured a thick slab on the ground and built
up a cement block tower to the height I wanted. The weight of the tank and
water place no load whatsoever on any part of the house.

Dixon