supporting 20G long by long sides alone

[Flying Squirrel]

Question: Is it safe to mount an aquarium (20 gallons, long) so that it
rests on rails along the long sides, but not the short sides? From
eyeballing it it looks this should be safe, but a word or two of authority
would be reassuring.

[Toni]

"Flying Squirrel" > wrote in message
...
> Question: Is it safe to mount an aquarium (20 gallons, long) so that it
> rests on rails along the long sides, but not the short sides? From
> eyeballing it it looks this should be safe, but a word or two of authority
> would be reassuring.
>
>


FWIW my 55 gallon sump is supported that way- leak free for 6+ months now.
I don't know that it is recommended- just my experience.


--
Toni
http://www.cearbhaill.com/discus.htm

[Harry Muscle]

"Flying Squirrel" > wrote in message
...
> Question: Is it safe to mount an aquarium (20 gallons, long) so tha
> sts on rails along the long sides, but not the short sides? From
> eyeballing it it looks this should be safe, but a word or two of authority
> would be reassuring.
>
>

If you want to have piece of mind, then no it's not safe, you're increasing
your chance of a leak (there's a reason why there are four sides that
usually get supported). If you don't mind a sudden leak down the road, then
chances are it will work for some time, how long, no one knows.

Harry

[NetMax]

"Flying Squirrel" > wrote in message
...
> Question: Is it safe to mount an aquarium (20 gallons, long) so that it
> rests on rails along the long sides, but not the short sides? From
> eyeballing it it looks this should be safe, but a word or two of
authority
> would be reassuring.

From my experience, no problem. For smaller tanks, I sometimes have them
held up by only a rail a few inches in from the short sides! The only
concern is that the stand is flat, so no twist stress is added. There
have been metal stands manufactured which had the end rails lower than
the sides, so the ends didn't support the tank at all.

Personally, I think you could hold up many types of tanks by a wood block
in each corner. The tank's base is held by the long sides, and the
amount of pressure needed to vertically break a pane of glass in a
vertical position should require many more times the amount of weight in
the tank. The only concern is again, that the 4 corner blocks equally
contact the glass so no twist is introduced.

When you put an empty tank on a stand, slide something thin under the
corners to check to see if there is a gap. That gap will usually
disappear when the tank is filled, but the size of the gap indicates how
much your silicone needs to stretch to compensate. The more it is
stretched, the less protection is remaining. Tanks don't usually come
apart (only mine do that ;~). They develop a leak from an existing hole
in the silicone, or from being stretched, the develop a leak.
Infrequently, some tanks will not flex to fill a gap, and you can always
slide paper under one corner. Not sure how safe this is (better or worst
than having the silicone flexing?), but it usually only happens with
small tanks.

Other considerations, stand type affects stability (during parties,
earthquakes, kids climbing etc), and tank quality (thickness of glass)
affects it's ability to absorb stand imperfections. For most
applications, check and fill gap with suitable material as applicable,
fill tank, jump up & down to check sway, secure stand as applicable.
Based on size, weight and orientation to floor, check floor. Based on
floor material, check stand's 'footprint' for floor damage.
--
www.NetMax.tk

[sophie]

In message >, NetMax
> writes

<snip>

> Based on
>floor material, check stand's 'footprint' for floor damage.

I have wondered about this, largely in connections with my bath, which
when full of water and me and the occasional small child insisting on
getting in, must weigh more than a 60ish (US) gallon tank full of water,
and assumed that the way it's spread (c.f. stiletto heels) is the
problem. I'd thought that if the stand has 4 "feet" rather than a base
I'd put a piece of (for example) exterior ply underneath do stop it
digging holes in the floorboards. Does this make any sense at all?

--
sophie

[CanadianCray]

For a 20gal tank no problem......

--
Craig Williams
_________________________________

www.Canadiancray.tk
"Flying Squirrel" > wrote in message
...
> Question: Is it safe to mount an aquarium (20 gallons, long) so that it
> rests on rails along the long sides, but not the short sides? From
> eyeballing it it looks this should be safe, but a word or two of authority
> would be reassuring.
>
>

[The Outcaste]

On Tue, 8 Jun 2004 10:47:31 -0400, "NetMax"
> bubbled forth the following:

>Personally, I think you could hold up many types of tanks by a wood block
>in each corner. The tank's base is held by the long sides, and the
>amount of pressure needed to vertically break a pane of glass in a
>vertical position should require many more times the amount of weight in
>the tank. The only concern is again, that the 4 corner blocks equally
>contact the glass so no twist is introduced.
While I've done this with small tanks (5 and 10 gal), I'd be a bit
leery with anything much larger.

There's one website (can't find the link now) where they recommend
that the 4 sides of the aquarium extend below the bottom panel. This
is so you don't have to build a frame to hold the bottom panel up off
of a solid topped stand. In this case the bottom panel is only held by
the silicone, with not even the support of wood blocks under each
corner. However, I'm not so sure I'd want to put that much faith in
the strength of the silicone. The bottom joint will be under more
stress this way, not only the water pressure pushing the side panel
out, but the weight of the water and decorations pushing the bottom
panel down.

Most DIY sites show that the side panels should be resting on the
bottom panel. All manufactured glass tanks I've seen are built this
way. The forces on the bottom joint are mainly shear (water pressure
pushing the side panel out), with some compression from the weight of
the vertical panes. When you only support the 4 corners, you are
asking the silicone to hold the bottom pane up to the vertical panes,
which places the joint in both tension and shear, and silicone is
stronger under shear than tension IIRC. While it may hold for years,
you may be stressing the silicone to the breaking point. I have this
mental picture of very small earthquake, or just a 2 pound rock
slipping from your hand a few inches above the substrate being the
proverbial last straw. causing the joint to fail all at once, opening
up like a zipper, causing the bottom pane to break into many pieces.

Plus I'm sure this would void any warranty on the tank.

I have no scientific or experiential data to say it won't work, but
that mental picture makes me rather be safe than sorry, though as
always, ymmv

Jerry

[NetMax]

"The Outcaste" > wrote in message
...
> On Tue, 8 Jun 2004 10:47:31 -0400, "NetMax"
> > bubbled forth the following:
>
> >Personally, I think you could hold up many types of tanks by a wood
block
> >in each corner. The tank's base is held by the long sides, and the
> >amount of pressure needed to vertically break a pane of glass in a
> >vertical position should require many more times the amount of weight
in
> >the tank. The only concern is again, that the 4 corner blocks equally
> >contact the glass so no twist is introduced.
> While I've done this with small tanks (5 and 10 gal), I'd be a bit
> leery with anything much larger.
>
> There's one website (can't find the link now) where they recommend
> that the 4 sides of the aquarium extend below the bottom panel. This
> is so you don't have to build a frame to hold the bottom panel up off
> of a solid topped stand. In this case the bottom panel is only held by
> the silicone, with not even the support of wood blocks under each
> corner. However, I'm not so sure I'd want to put that much faith in
> the strength of the silicone. The bottom joint will be under more
> stress this way, not only the water pressure pushing the side panel
> out, but the weight of the water and decorations pushing the bottom
> panel down.
>
> Most DIY sites show that the side panels should be resting on the
> bottom panel. All manufactured glass tanks I've seen are built this
> way. The forces on the bottom joint are mainly shear (water pressure
> pushing the side panel out), with some compression from the weight of
> the vertical panes. When you only support the 4 corners, you are
> asking the silicone to hold the bottom pane up to the vertical panes,
> which places the joint in both tension and shear, and silicone is
> stronger under shear than tension IIRC. While it may hold for years,
> you may be stressing the silicone to the breaking point. I have this
> mental picture of very small earthquake, or just a 2 pound rock
> slipping from your hand a few inches above the substrate being the
> proverbial last straw. causing the joint to fail all at once, opening
> up like a zipper, causing the bottom pane to break into many pieces.
>
> Plus I'm sure this would void any warranty on the tank.
>
> I have no scientific or experiential data to say it won't work, but
> that mental picture makes me rather be safe than sorry, though as
> always, ymmv
>
> Jerry

What country are you in? From Europe & Asia, I tend to see more flat
bottom tanks (glass sides sit on bottom pane as you described), but the
bottom trim raises the bottom so it doesn't touch the stand. From North
American manufacturers, it mostly seems to be the opposite, where the
tank sits on the glass sides, with the bottom siliconed inside and above
the stand. I'm not familiar with the pros & cons, but it would surely
affect the jigging needed to build them. When I look at functional
design advantages and at manufacturing advantages, I see merit in both
designs, at least similar enough that there isn't an obvious better
design.

In case you are wondering where the edge bottom has a structural
advantage over the pane bottom, if we assume that the silcone bead
exceeds the worst case weight condtion in the edge bottom design, then
there is a superior bond between the bottom and the side panes with this
configuration. To explain in text is a bit labourous, but I'll do my
best. With a pane bottom design you mentioned, there are 2 silicone
beads. Bead 1 is between the glass surfaces and bead 2 is a chamfered
bead running inside the tank (on top). With the edge bottom design,
there are 3 silicone beads, between the glass surfaces, and a chamfered
bead on each side of the bottom pane. An argument could be made that the
strongest vector of concern is pushing outward on the side panes at the
very bottom, so 3 beads are slightly stronger than 2 (even if all 3 are
in line with the side vector, while the 2 bead design has 1 bead
perpendicular to the side vector).

If I sound like I know more than I do, then you are right ;~). I'm not a
mechanical engineer, but it's puzzled me how 2 different designs have
continued to co-exist. I don't think the average buyer notices one from
the other, so it would seem to be driven by internal forces rather than
consumers.
--
www.NetMax.tk

[The Outcaste]

mid posted

On Tue, 8 Jun 2004 16:38:11 -0400, "NetMax"
> bubbled forth the following:

>"The Outcaste" > wrote in message
...
>> On Tue, 8 Jun 2004 10:47:31 -0400, "NetMax"
>> > bubbled forth the following:
>>
>> >Personally, I think you could hold up many types of tanks by a wood
>block
>> >in each corner. The tank's base is held by the long sides, and the
>> >amount of pressure needed to vertically break a pane of glass in a
>> >vertical position should require many more times the amount of weight
>in
>> >the tank. The only concern is again, that the 4 corner blocks equally
>> >contact the glass so no twist is introduced.
>> While I've done this with small tanks (5 and 10 gal), I'd be a bit
>> leery with anything much larger.
>>
>> There's one website (can't find the link now) where they recommend
>> that the 4 sides of the aquarium extend below the bottom panel. This
>> is so you don't have to build a frame to hold the bottom panel up off
>> of a solid topped stand. In this case the bottom panel is only held by
>> the silicone, with not even the support of wood blocks under each
>> corner. However, I'm not so sure I'd want to put that much faith in
>> the strength of the silicone. The bottom joint will be under more
>> stress this way, not only the water pressure pushing the side panel
>> out, but the weight of the water and decorations pushing the bottom
>> panel down.
>>
>> Most DIY sites show that the side panels should be resting on the
>> bottom panel. All manufactured glass tanks I've seen are built this
>> way. The forces on the bottom joint are mainly shear (water pressure
>> pushing the side panel out), with some compression from the weight of
>> the vertical panes. When you only support the 4 corners, you are
>> asking the silicone to hold the bottom pane up to the vertical panes,
>> which places the joint in both tension and shear, and silicone is
>> stronger under shear than tension IIRC. While it may hold for years,
>> you may be stressing the silicone to the breaking point. I have this
>> mental picture of very small earthquake, or just a 2 pound rock
>> slipping from your hand a few inches above the substrate being the
>> proverbial last straw. causing the joint to fail all at once, opening
>> up like a zipper, causing the bottom pane to break into many pieces.
>>
>> Plus I'm sure this would void any warranty on the tank.
>>
>> I have no scientific or experiential data to say it won't work, but
>> that mental picture makes me rather be safe than sorry, though as
>> always, ymmv
>>
>> Jerry
>
>What country are you in?

US, Portland, OR, 2878.4 miles from your store.

> From Europe & Asia, I tend to see more flat
>bottom tanks (glass sides sit on bottom pane as you described), but the
>bottom trim raises the bottom so it doesn't touch the stand. From North
>American manufacturers, it mostly seems to be the opposite, where the
>tank sits on the glass sides, with the bottom siliconed inside and above
>the stand. I'm not familiar with the pros & cons, but it would surely
>affect the jigging needed to build them. When I look at functional
>design advantages and at manufacturing advantages, I see merit in both
>designs, at least similar enough that there isn't an obvious better
>design.
>
Just double checked my 2 10 gal tanks. With the plastic bottom frame,
it's hard to tell, but there is enough of a gap on one to see that at
least the front pane sits on top of the bottom pane. I managed to
slide one corner off of the end table check from the bottom and the
bottom pane rests right on the plastic frame -- there is no room for a
3rd bead of silicone, though the frame its self would add some
structural support to the bottom pane. They were manufactured by
Island Aquarium, Fontana, CA

My impression of the larger tanks I've looked at in the LFS is that
the sides sit on the bottom, but with the bottom frame it's hard to
tell, so I could well be wrong.
>
>In case you are wondering where the edge bottom has a structural
>advantage over the pane bottom, if we assume that the silcone bead
>exceeds the worst case weight condtion in the edge bottom design, then
>there is a superior bond between the bottom and the side panes with this
>configuration. To explain in text is a bit labourous, but I'll do my
>best. With a pane bottom design you mentioned, there are 2 silicone
>beads. Bead 1 is between the glass surfaces and bead 2 is a chamfered
>bead running inside the tank (on top). With the edge bottom design,
>there are 3 silicone beads, between the glass surfaces, and a chamfered
>bead on each side of the bottom pane. An argument could be made that the
>strongest vector of concern is pushing outward on the side panes at the
>very bottom, so 3 beads are slightly stronger than 2 (even if all 3 are
>in line with the side vector, while the 2 bead design has 1 bead
>perpendicular to the side vector).
>
The 3rd bead on the bottom side could well give a structural
advantage.
>
>If I sound like I know more than I do, then you are right ;~). I'm not a
>mechanical engineer, but it's puzzled me how 2 different designs have
>continued to co-exist. I don't think the average buyer notices one from
>the other, so it would seem to be driven by internal forces rather than
>consumers.
>
I did finally track down the web site that mentions the edge bottom
method, it's http://www.garf.org/tank/buildtank.asp
Here is their only reason for this type of construction:
"It is important that the weight of the aquarium is supported by the
front, back and sides. There should never be any support under the
bottom glass as this could fracture it."

They don't go into much detail on applying the silicone, basically
apply to edges and stick together. If it leaks, then run a bead along
the inside, nothing about adding a bead on the bottom of the bottom
pane

Conversely, after checking several other DIY sites, they all say the
front, back and sides must sit on the bottom pane, but never say *Why*
this is so.

I did some digging on the GE Silicone web site and found the following
info for their Construction SCS1201 silicone I found under
construction/glazing/aquarium
http://www.gesilicones.com/silicones/americas/business/industries/construction/glazing/aquarium/

It shows the tensile strength is 470 psi, and the peel strength is 40
lb/in. From what I can find on how peel strength is determined, this
is what I have been calling shear stress, or the downward force on the
bottom plate of the edge bottom style tank.

Now keep in mind that my back ground is electronic engineering, not
mechanical, so I may be way off on these numbers. The peel strength of
40 lb/in means 40 lb force per inch of bond line at 180 ° angle. I
don't know if this requires the bond line to be 1 in width for each in
of length (ie, 1 sq in) but the tests are done with a 1 sq in patch. I
doubt if the strength is linear with the width of the bond, but if we
assume it is, a 1/4" bond would give 10 lb/in, so:

Take a 48"x18" piece of 1/4" glass. It's perimeter is 132 inches. At
10lbs/in, it can support 1320 lbs. The depth of water to equal 1320
pounds (158 gal) would be 42 inches. With a 1/4" base I wouldn't go
more than 12"-14" deep, so there appears to be a safety factor of at
least 3 (42/14). And this doesn't include the additional strength of
the 2nd and 3rd bead. As far as the outward force, 1/4*48 gives 12 sq
in of bond*470 psi= 5640 pounds -- that would take 676 gallons with
all the weight acting solely on the one edge. So looks like the peel
strength is the limiting factor.

So if my assumptions and calculations are correct, while the bottom
plate construction may be stronger, in practical application the
silicone is strong enough that it doesn't make any difference which
way you assemble it.

Comments and corrections of my assumptions are welcome.

Jerry

[Marcel Beaudoin]

sophie > wrote in
:

> I have wondered about this, largely in connections with my bath, which
> when full of water and me and the occasional small child insisting on
> getting in, must weigh more than a 60ish (US) gallon tank full of
> water, and assumed that the way it's spread (c.f. stiletto heels) is
> the problem. I'd thought that if the stand has 4 "feet" rather than a
> base I'd put a piece of (for example) exterior ply underneath do stop
> it digging holes in the floorboards. Does this make any sense at all?

Yup. That is why they try to discourage stilletto heals on airplanes. As
you decrease the area of something which is standing on something else,
the pressure increases. Try it with a pencil. Press the eraser against
your hand and then switch it over and do the same with the sharpened
end...

Marcel

[sophie]

In message >, Marcel
Beaudoin > writes
>sophie > wrote in
:
>
>> I have wondered about this, largely in connections with my bath, which
>> when full of water and me and the occasional small child insisting on
>> getting in, must weigh more than a 60ish (US) gallon tank full of
>> water, and assumed that the way it's spread (c.f. stiletto heels) is
>> the problem. I'd thought that if the stand has 4 "feet" rather than a
>> base I'd put a piece of (for example) exterior ply underneath do stop
>> it digging holes in the floorboards. Does this make any sense at all?
>
>Yup. That is why they try to discourage stilletto heals on airplanes. As
>you decrease the area of something which is standing on something else,
>the pressure increases. Try it with a pencil. Press the eraser against
>your hand and then switch it over and do the same with the sharpened
>end...

I understand about pressure and the area to which a force is applied, I
was wondering more about the strength of my floorboards!
--
sophie

[Marcel Beaudoin]

sophie > wrote in
:

> I'd thought that if the stand has 4 "feet" rather than a
>>> base I'd put a piece of (for example) exterior ply underneath do
>>> stop it digging holes in the floorboards. Does this make any sense
>>> at all?
>>
>>Yup. That is why they try to discourage stilletto heals on airplanes.
>>As you decrease the area of something which is standing on something
>>else, the pressure increases. Try it with a pencil. Press the eraser
>>against your hand and then switch it over and do the same with the
>>sharpened end...
>
> I understand about pressure and the area to which a force is applied,
> I was wondering more about the strength of my floorboards!

Ahhh. Oops. But yeah, that should work. You wouldn't even need to put a
whole piece of ply underneath. A piece a couple of inches square would do
the job.

Marcel

[sophie]

In message >, Marcel
Beaudoin > writes
>sophie > wrote in
:
>
>> I'd thought that if the stand has 4 "feet" rather than a
>>>> base I'd put a piece of (for example) exterior ply underneath do
>>>> stop it digging holes in the floorboards. Does this make any sense
>>>> at all?
>>>
>>>Yup. That is why they try to discourage stilletto heals on airplanes.
>>>As you decrease the area of something which is standing on something
>>>else, the pressure increases. Try it with a pencil. Press the eraser
>>>against your hand and then switch it over and do the same with the
>>>sharpened end...
>>
>> I understand about pressure and the area to which a force is applied,
>> I was wondering more about the strength of my floorboards!
>
>Ahhh. Oops. But yeah, that should work. You wouldn't even need to put a
>whole piece of ply underneath. A piece a couple of inches square would do
>the job.

thanks, Marcel, that would certainly be less unattractive!
--
sophie

[Dave]

"The Outcaste" > wrote in message
...
> mid posted
>
> On Tue, 8 Jun 2004 16:38:11 -0400, "NetMax"
> > bubbled forth the following:
>
> >"The Outcaste" > wrote in message
> ...
> >> On Tue, 8 Jun 2004 10:47:31 -0400, "NetMax"
> >> > bubbled forth the following:
> >>
> >> >Personally, I think you could hold up many types of tanks by a wood
> >block
> >> >in each corner. The tank's base is held by the long sides, and the
> >> >amount of pressure needed to vertically break a pane of glass in a
> >> >vertical position should require many more times the amount of weight
> >in
> >> >the tank. The only concern is again, that the 4 corner blocks equally
> >> >contact the glass so no twist is introduced.
> >> While I've done this with small tanks (5 and 10 gal), I'd be a bit
> >> leery with anything much larger.
> >>
> >> There's one website (can't find the link now) where they recommend
> >> that the 4 sides of the aquarium extend below the bottom panel. This
> >> is so you don't have to build a frame to hold the bottom panel up off
> >> of a solid topped stand. In this case the bottom panel is only held by
> >> the silicone, with not even the support of wood blocks under each
> >> corner. However, I'm not so sure I'd want to put that much faith in
> >> the strength of the silicone. The bottom joint will be under more
> >> stress this way, not only the water pressure pushing the side panel
> >> out, but the weight of the water and decorations pushing the bottom
> >> panel down.
> >>
> >> Most DIY sites show that the side panels should be resting on the
> >> bottom panel. All manufactured glass tanks I've seen are built this
> >> way. The forces on the bottom joint are mainly shear (water pressure
> >> pushing the side panel out), with some compression from the weight of
> >> the vertical panes. When you only support the 4 corners, you are
> >> asking the silicone to hold the bottom pane up to the vertical panes,
> >> which places the joint in both tension and shear, and silicone is
> >> stronger under shear than tension IIRC. While it may hold for years,
> >> you may be stressing the silicone to the breaking point. I have this
> >> mental picture of very small earthquake, or just a 2 pound rock
> >> slipping from your hand a few inches above the substrate being the
> >> proverbial last straw. causing the joint to fail all at once, opening
> >> up like a zipper, causing the bottom pane to break into many pieces.
> >>
> >> Plus I'm sure this would void any warranty on the tank.
> >>
> >> I have no scientific or experiential data to say it won't work, but
> >> that mental picture makes me rather be safe than sorry, though as
> >> always, ymmv
> >>
> >> Jerry
> >
> >What country are you in?
>
> US, Portland, OR, 2878.4 miles from your store.
>
> > From Europe & Asia, I tend to see more flat
> >bottom tanks (glass sides sit on bottom pane as you described), but the
> >bottom trim raises the bottom so it doesn't touch the stand. From North
> >American manufacturers, it mostly seems to be the opposite, where the
> >tank sits on the glass sides, with the bottom siliconed inside and above
> >the stand. I'm not familiar with the pros & cons, but it would surely
> >affect the jigging needed to build them. When I look at functional
> >design advantages and at manufacturing advantages, I see merit in both
> >designs, at least similar enough that there isn't an obvious better
> >design.
> >
> Just double checked my 2 10 gal tanks. With the plastic bottom frame,
> it's hard to tell, but there is enough of a gap on one to see that at
> least the front pane sits on top of the bottom pane. I managed to
> slide one corner off of the end table check from the bottom and the
> bottom pane rests right on the plastic frame -- there is no room for a
> 3rd bead of silicone, though the frame its self would add some
> structural support to the bottom pane. They were manufactured by
> Island Aquarium, Fontana, CA
>
> My impression of the larger tanks I've looked at in the LFS is that
> the sides sit on the bottom, but with the bottom frame it's hard to
> tell, so I could well be wrong.
> >
> >In case you are wondering where the edge bottom has a structural
> >advantage over the pane bottom, if we assume that the silcone bead
> >exceeds the worst case weight condtion in the edge bottom design, then
> >there is a superior bond between the bottom and the side panes with this
> >configuration. To explain in text is a bit labourous, but I'll do my
> >best. With a pane bottom design you mentioned, there are 2 silicone
> >beads. Bead 1 is between the glass surfaces and bead 2 is a chamfered
> >bead running inside the tank (on top). With the edge bottom design,
> >there are 3 silicone beads, between the glass surfaces, and a chamfered
> >bead on each side of the bottom pane. An argument could be made that the
> >strongest vector of concern is pushing outward on the side panes at the
> >very bottom, so 3 beads are slightly stronger than 2 (even if all 3 are
> >in line with the side vector, while the 2 bead design has 1 bead
> >perpendicular to the side vector).
> >
> The 3rd bead on the bottom side could well give a structural
> advantage.
> >
> >If I sound like I know more than I do, then you are right ;~). I'm not a
> >mechanical engineer, but it's puzzled me how 2 different designs have
> >continued to co-exist. I don't think the average buyer notices one from
> >the other, so it would seem to be driven by internal forces rather than
> >consumers.
> >
> I did finally track down the web site that mentions the edge bottom
> method, it's http://www.garf.org/tank/buildtank.asp
> Here is their only reason for this type of construction:
> "It is important that the weight of the aquarium is supported by the
> front, back and sides. There should never be any support under the
> bottom glass as this could fracture it."
>
> They don't go into much detail on applying the silicone, basically
> apply to edges and stick together. If it leaks, then run a bead along
> the inside, nothing about adding a bead on the bottom of the bottom
> pane
>
> Conversely, after checking several other DIY sites, they all say the
> front, back and sides must sit on the bottom pane, but never say *Why*
> this is so.
>
> I did some digging on the GE Silicone web site and found the following
> info for their Construction SCS1201 silicone I found under
> construction/glazing/aquarium
>
http://www.gesilicones.com/silicones/americas/business/industries/construction/glazing/aquarium/
>
> It shows the tensile strength is 470 psi, and the peel strength is 40
> lb/in. From what I can find on how peel strength is determined, this
> is what I have been calling shear stress, or the downward force on the
> bottom plate of the edge bottom style tank.
>
> Now keep in mind that my back ground is electronic engineering, not
> mechanical, so I may be way off on these numbers. The peel strength of
> 40 lb/in means 40 lb force per inch of bond line at 180 ° angle. I
> don't know if this requires the bond line to be 1 in width for each in
> of length (ie, 1 sq in) but the tests are done with a 1 sq in patch. I
> doubt if the strength is linear with the width of the bond, but if we
> assume it is, a 1/4" bond would give 10 lb/in, so:
>
> Take a 48"x18" piece of 1/4" glass. It's perimeter is 132 inches. At
> 10lbs/in, it can support 1320 lbs. The depth of water to equal 1320
> pounds (158 gal) would be 42 inches. With a 1/4" base I wouldn't go
> more than 12"-14" deep, so there appears to be a safety factor of at
> least 3 (42/14). And this doesn't include the additional strength of
> the 2nd and 3rd bead. As far as the outward force, 1/4*48 gives 12 sq
> in of bond*470 psi= 5640 pounds -- that would take 676 gallons with
> all the weight acting solely on the one edge. So looks like the peel
> strength is the limiting factor.
>
> So if my assumptions and calculations are correct, while the bottom
> plate construction may be stronger, in practical application the
> silicone is strong enough that it doesn't make any difference which
> way you assemble it.
>
> Comments and corrections of my assumptions are welcome.
>
> Jerry
>

Nice calculations.... I believe the prime bonding strength to be the edge to
edge
contact area, with a very thin layer of silicone sandwiched by the glass.
This
area takes the bulk sheer. I am led to believe the chamfered beads placed
inside/
outside supply only water proofing where the prime contact bond is
perforated.

The two construction types each have their own advantages/disadvantages.
The
bottom supported type has to be supported equally otherwise undue stresses
are
applied. The force of the water at the bottom of the tank pushes outwards,
therefore
the stress here is outwards, walls pushed off base = peel/sheer.

The side wall supported tank is different as this can be supported anywhere
so long as the supports are flat. The disadvantage here is when an edge is
chipped/
micro fractured and is only supported by the corners. Think the stiletto
effect of women's
shoes. The tensile strength of glass along its edge is stronger. The SAME
force of the
water at the bottom of the tank pushes downwards, therefore
the stress here is downwards, base pushed off/down walls = peel/sheer.

The two stress vectors are of equal magnitude, just looking at it from
different angles. IMHO the
best design is just up to personal preference.

Dave.

[NetMax]

"Dave" > wrote in message
news:5gtyc.307$n35.99@newsfe2-win...
>
> "The Outcaste" > wrote in message
> ...
> > mid posted
> >
> > On Tue, 8 Jun 2004 16:38:11 -0400, "NetMax"
> > > bubbled forth the following:
> >
> > >"The Outcaste" > wrote in message
> > ...
> > >> On Tue, 8 Jun 2004 10:47:31 -0400, "NetMax"
> > >> > bubbled forth the following:
> > >>
> > >> >Personally, I think you could hold up many types of tanks by a
wood
> > >block
> > >> >in each corner. The tank's base is held by the long sides, and
the
> > >> >amount of pressure needed to vertically break a pane of glass in
a
> > >> >vertical position should require many more times the amount of
weight
> > >in
> > >> >the tank. The only concern is again, that the 4 corner blocks
equally
> > >> >contact the glass so no twist is introduced.
> > >> While I've done this with small tanks (5 and 10 gal), I'd be a bit
> > >> leery with anything much larger.
> > >>
> > >> There's one website (can't find the link now) where they recommend
> > >> that the 4 sides of the aquarium extend below the bottom panel.
This
> > >> is so you don't have to build a frame to hold the bottom panel up
off
> > >> of a solid topped stand. In this case the bottom panel is only
held by
> > >> the silicone, with not even the support of wood blocks under each
> > >> corner. However, I'm not so sure I'd want to put that much faith
in
> > >> the strength of the silicone. The bottom joint will be under more
> > >> stress this way, not only the water pressure pushing the side
panel
> > >> out, but the weight of the water and decorations pushing the
bottom
> > >> panel down.
> > >>
> > >> Most DIY sites show that the side panels should be resting on the
> > >> bottom panel. All manufactured glass tanks I've seen are built
this
> > >> way. The forces on the bottom joint are mainly shear (water
pressure
> > >> pushing the side panel out), with some compression from the weight
of
> > >> the vertical panes. When you only support the 4 corners, you are
> > >> asking the silicone to hold the bottom pane up to the vertical
panes,
> > >> which places the joint in both tension and shear, and silicone is
> > >> stronger under shear than tension IIRC. While it may hold for
years,
> > >> you may be stressing the silicone to the breaking point. I have
this
> > >> mental picture of very small earthquake, or just a 2 pound rock
> > >> slipping from your hand a few inches above the substrate being the
> > >> proverbial last straw. causing the joint to fail all at once,
opening
> > >> up like a zipper, causing the bottom pane to break into many
pieces.
> > >>
> > >> Plus I'm sure this would void any warranty on the tank.
> > >>
> > >> I have no scientific or experiential data to say it won't work,
but
> > >> that mental picture makes me rather be safe than sorry, though as
> > >> always, ymmv
> > >>
> > >> Jerry
> > >
> > >What country are you in?
> >
> > US, Portland, OR, 2878.4 miles from your store.
> >
> > > From Europe & Asia, I tend to see more flat
> > >bottom tanks (glass sides sit on bottom pane as you described), but
the
> > >bottom trim raises the bottom so it doesn't touch the stand. From
North
> > >American manufacturers, it mostly seems to be the opposite, where
the
> > >tank sits on the glass sides, with the bottom siliconed inside and
above
> > >the stand. I'm not familiar with the pros & cons, but it would
surely
> > >affect the jigging needed to build them. When I look at functional
> > >design advantages and at manufacturing advantages, I see merit in
both
> > >designs, at least similar enough that there isn't an obvious better
> > >design.
> > >
> > Just double checked my 2 10 gal tanks. With the plastic bottom frame,
> > it's hard to tell, but there is enough of a gap on one to see that at
> > least the front pane sits on top of the bottom pane. I managed to
> > slide one corner off of the end table check from the bottom and the
> > bottom pane rests right on the plastic frame -- there is no room for
a
> > 3rd bead of silicone, though the frame its self would add some
> > structural support to the bottom pane. They were manufactured by
> > Island Aquarium, Fontana, CA
> >
> > My impression of the larger tanks I've looked at in the LFS is that
> > the sides sit on the bottom, but with the bottom frame it's hard to
> > tell, so I could well be wrong.
> > >
> > >In case you are wondering where the edge bottom has a structural
> > >advantage over the pane bottom, if we assume that the silcone bead
> > >exceeds the worst case weight condtion in the edge bottom design,
then
> > >there is a superior bond between the bottom and the side panes with
this
> > >configuration. To explain in text is a bit labourous, but I'll do
my
> > >best. With a pane bottom design you mentioned, there are 2 silicone
> > >beads. Bead 1 is between the glass surfaces and bead 2 is a
chamfered
> > >bead running inside the tank (on top). With the edge bottom design,
> > >there are 3 silicone beads, between the glass surfaces, and a
chamfered
> > >bead on each side of the bottom pane. An argument could be made
that the
> > >strongest vector of concern is pushing outward on the side panes at
the
> > >very bottom, so 3 beads are slightly stronger than 2 (even if all 3
are
> > >in line with the side vector, while the 2 bead design has 1 bead
> > >perpendicular to the side vector).
> > >
> > The 3rd bead on the bottom side could well give a structural
> > advantage.
> > >
> > >If I sound like I know more than I do, then you are right ;~). I'm
not a
> > >mechanical engineer, but it's puzzled me how 2 different designs
have
> > >continued to co-exist. I don't think the average buyer notices one
from
> > >the other, so it would seem to be driven by internal forces rather
than
> > >consumers.
> > >
> > I did finally track down the web site that mentions the edge bottom
> > method, it's http://www.garf.org/tank/buildtank.asp
> > Here is their only reason for this type of construction:
> > "It is important that the weight of the aquarium is supported by the
> > front, back and sides. There should never be any support under the
> > bottom glass as this could fracture it."
> >
> > They don't go into much detail on applying the silicone, basically
> > apply to edges and stick together. If it leaks, then run a bead along
> > the inside, nothing about adding a bead on the bottom of the bottom
> > pane
> >
> > Conversely, after checking several other DIY sites, they all say the
> > front, back and sides must sit on the bottom pane, but never say
*Why*
> > this is so.
> >
> > I did some digging on the GE Silicone web site and found the
following
> > info for their Construction SCS1201 silicone I found under
> > construction/glazing/aquarium
> >
>
http://www.gesilicones.com/silicones/americas/business/industries/construction/glazing/aquarium/
> >
> > It shows the tensile strength is 470 psi, and the peel strength is 40
> > lb/in. From what I can find on how peel strength is determined, this
> > is what I have been calling shear stress, or the downward force on
the
> > bottom plate of the edge bottom style tank.
> >
> > Now keep in mind that my back ground is electronic engineering, not
> > mechanical, so I may be way off on these numbers. The peel strength
of
> > 40 lb/in means 40 lb force per inch of bond line at 180 ° angle. I
> > don't know if this requires the bond line to be 1 in width for each
in
> > of length (ie, 1 sq in) but the tests are done with a 1 sq in patch.
I
> > doubt if the strength is linear with the width of the bond, but if we
> > assume it is, a 1/4" bond would give 10 lb/in, so:
> >
> > Take a 48"x18" piece of 1/4" glass. It's perimeter is 132 inches. At
> > 10lbs/in, it can support 1320 lbs. The depth of water to equal 1320
> > pounds (158 gal) would be 42 inches. With a 1/4" base I wouldn't go
> > more than 12"-14" deep, so there appears to be a safety factor of at
> > least 3 (42/14). And this doesn't include the additional strength of
> > the 2nd and 3rd bead. As far as the outward force, 1/4*48 gives 12
sq
> > in of bond*470 psi= 5640 pounds -- that would take 676 gallons with
> > all the weight acting solely on the one edge. So looks like the peel
> > strength is the limiting factor.
> >
> > So if my assumptions and calculations are correct, while the bottom
> > plate construction may be stronger, in practical application the
> > silicone is strong enough that it doesn't make any difference which
> > way you assemble it.
> >
> > Comments and corrections of my assumptions are welcome.
> >
> > Jerry
> >
>
> Nice calculations.... I believe the prime bonding strength to be the
edge to
> edge
> contact area, with a very thin layer of silicone sandwiched by the
glass.
> This
> area takes the bulk sheer. I am led to believe the chamfered beads
placed
> inside/
> outside supply only water proofing where the prime contact bond is
> perforated.
>
> The two construction types each have their own
advantages/disadvantages.
> The
> bottom supported type has to be supported equally otherwise undue
stresses
> are
> applied. The force of the water at the bottom of the tank pushes
outwards,
> therefore
> the stress here is outwards, walls pushed off base = peel/sheer.
>
> The side wall supported tank is different as this can be supported
anywhere
> so long as the supports are flat. The disadvantage here is when an edge
is
> chipped/
> micro fractured and is only supported by the corners. Think the
stiletto
> effect of women's
> shoes. The tensile strength of glass along its edge is stronger. The
SAME
> force of the
> water at the bottom of the tank pushes downwards, therefore
> the stress here is downwards, base pushed off/down walls = peel/sheer.
>
> The two stress vectors are of equal magnitude, just looking at it from
> different angles. IMHO the
> best design is just up to personal preference.
>
> Dave.

Jerry, yes, good stuff on the calculations. Unfortunately, my background
is also electrical engineering and not mechanical. While all my tanks at
home have a raised bottom, I'm going to look more closely at the newer
ones at work. You are right about the plastic trim interfering with
being able to see their construction. I could be wrong about the
European vs North American trend as they could have started changing over
and I haven't been watching for it. It's when I carry tanks around the
fish room that I notice the gap, and I *think* the manufacturers I carry
are mostly raised bottom, but I'm going to start paying more attention to
it.

Dave, on your comments about which beads have the most structural
function, this has been my understanding as well. The inside bead is a
secondary element for the structure's integrity, proving an additional
layer of safety for waterproofing and helping prevent the main seal from
damage due to the occupants. I'd also read that the physical limit of
silicone occurs at around 48" of depth, so tanks are usually not
constructed taller than 36" to maintain a safety margin (but I think I
read it on a web site, so who know?). I suppose keeping a stainless
steel frame around the base or the top would address this. Before my
120g split open, I was thinking of putting a pipe clamp on the end about
halfway up (I could see a lot of bubbles in the silicone). Of course,
the silicone gave out before I added the pipe clamp *argh*.
--
www.NetMax.tk

[AAA]

"Dave" > wrote in message
news:5gtyc.307$n35.99@newsfe2-win...
>
> > >> Most DIY sites show that the side panels should be resting on the
> > >> bottom panel. All manufactured glass tanks I've seen are built
this
> > >> way. The forces on the bottom joint are mainly shear (water
pressure
> > >> pushing the side panel out), with some compression from the
weight of
> > >> the vertical panes. When you only support the 4 corners, you are
> > >> asking the silicone to hold the bottom pane up to the vertical
panes,
> > >> which places the joint in both tension and shear, and silicone is
> > >> stronger under shear than tension IIRC. While it may hold for
years,
> > >> you may be stressing the silicone to the breaking point. I have
this
> > >> mental picture of very small earthquake, or just a 2 pound rock
> > >> slipping from your hand a few inches above the substrate being
the
> > >> proverbial last straw. causing the joint to fail all at once,
opening
> > >> up like a zipper, causing the bottom pane to break into many
pieces.

Now that would be cool to watch. Cleaning your 55g fish tank and
dropping a small rock or something and "whosh", the whole tank falls
into the base. Ever happen to anyone? I'd be LMAO for a year or so.
Sounds like a good stunt for one of those TV shows. Fish maintanice guy
shows up and starts to work, and "whosh"! LOL