Expected deflection in a 40b?

[djatl]

I just put water in my 40b frag tank (36x18 footprint), and while measuring for a mesh top, I noticed that the center bows out a little more than 1/8" at the top center compared to the ends. There's no center brace on it. Is this normal for a 40b? My 65g has the same footprint, but has a center brace, so I've never noticed any deflection. I hope I'm just being paranoid.

Thanks,
Doug

 

[CoralShop]

well, first, deflection as google defines it:
de·flec·tion

/diˈflekSHən/
Noun

<ul>
<li>The action or process of deflecting or being deflected.</li>
<li>The amount by which something is deflected.</li>
</ul>
I think you mean the glass is bowing or flexing.

Second, does it have a rim? If so, I wouldn't worry.

 

[djatl]

I was thinking of this definition, but bowing is another word to describe it:
http://en.wikipedia.org/wiki/Deflection_%28engineering%29">http://en.wikipedia.org/wiki/Deflection_%28engineering%29</a>[INDENT]In [IMG]http://en.wikipedia.org/wiki/Engineering">engineering</a>, [B]deflection[/B] is the degree to which a structural element is displaced under a [IMG]http://en.wikipedia.org/wiki/Force">load</a>. It may refer to an angle or a distance.
[/INDENT]Yes, it does have a rim. It's a used 40b, so I wanted to make sure what I was seeing wasn't unusual. Thanks for the input.

Thanks,
Doug

 

[CoralShop]

I thin it'll be fine I had a 20L do the same thing

 

[rdnelson]

djatl;832383 wrote: I was thinking of this definition, but bowing is another word to describe it:
http://en.wikipedia.org/wiki/Deflection_%28engineering%29">http://en.wikipedia.org/wiki/Deflection_%28engineering%29</a>[INDENT]In [IMG]http://en.wikipedia.org/wiki/Engineering">engineering</a>, [B]deflection[/B] is the degree to which a structural element is displaced under a [IMG]http://en.wikipedia.org/wiki/Force">load</a>. It may refer to an angle or a distance.
[/INDENT]. [/QUOTE]

That was my first thought. LOL. Most structural steel is fabricated with a camber to account for the expected deflection.

But to the original question, I had one for about 12 years that did exactly that. You should be fine.

 

[jef4y]

Dictionary.com:
de·flec·tion/d&#618;&#712;fl&#603;k&#643;&#601;n/ Show Spelled [dih-flek-shuhn] Show IPA
noun
1. the act or state of deflecting or the state of being deflected.
2. amount of deviation.
3. the deviation of the indicator of an instrument from the position taken as zero.
4. Optics. deviation ( def 5a ) .
5. Military . the angle formed by the line of sight to the target and the line of sight to the point at which a gun is aimed so as to strike the target.

Now let's look up Deflect:
de·flect/d&#618;&#712;fl&#603;kt/ Show Spelled [dih-flekt] Show IPA
verb (used with object), verb (used without object)
to bend or turn aside; turn from a true course or straight line; swerve.

Deflection is the right word here and perfectly appropriate for the application. Alternatively you can argue it with every engineer on the planet who deals with loads.

=)

====================================================

That said, glass will bow/deflect. As will Acrylic. If it's a standard tank, unmodified, I wouldn't worry about it. However, if it was a rimmed tank and you removed the rim, then I'd be a bit worried. 1/8 isn't bad. My 150 acrylic (5x2x2) has probably 1/2" or more at the center, and it IS braced across the top. It just puffs out like a beer belly.

 

[CoralShop]

I need to refresh my engineering knowledge clearly