Need help with Acrylic thickness / Viewing window

[Allseer12]

Hello everyone, been a long time viewer of these forums but have never posted until today.

To make a very long story short, I need some help. I'm in my pre-planning stages. I'm building a new house that'll be incorporating an indoor pond into the foundation.

Inside diameter of the tank is
12ft long
6ft wide
9ft tall with fill line right at 8ft

Viewing window will be a 4x8, concrete / steel reinforced on all sides placed 1 foot off the bottom of the tank.

Any insight to this calculation on acrylic thickness only will be greatly appreciated. Thank you!!

 

[M1A1]

Anything over 4-5 feet in water depth starts getting into museum exhibit levels of material thickness if you want to do it 'right' and not see any bowing at all. You're talking 8 feet water depth with the window 1 foot off the bottom of the tank so the bottom of the window sees 7 feet of water pressure - that's the critical dimension for calculations along with the size of the window itself. At that depth and with a safety factor of 4 then the recommended minimum acrylic thickness is 3.5 inches. Reducing the safety factor will reduce the minimum thickness but the window will bow outwards more and will put more stress on the steel reinforcement collar/frame.

 

[Allseer12]

Thank you so much for that! Been searching everywhere for a calculator on that pressure/ acrylic formula but can't seam to find one and every engineer i can fit the answer is over booked to even talk in my area lol. If you can help me with one more formula I'd be eternally grateful. What would I need for 4.5ft of head pressure if I did 2= 4x8 sheets for the viewing window supported in the center with steel and concrete? Basically 16ft of viewing window length wise. Again, thank you for your time!

 

[M1A1]

If I assume the center support column acts exactly like the rest of the window support area so it's basically 2 windows then acrylic thickness is 2.25 to 2.5 inches. If it was one continuous piece of acrylic (4x16ft) at 4.5ft water depth then the thickness is in the 2.5 to 3 inch range with normal safety factory (4).

 

[Backfromthedead]

I think 2.5" acrylic would hold up great as long as it's fully braced around the frame. Maybe even thinner than that but 2.5" would be no hesitation from me.

The bass pro shop near me has a window with no top brace about 12'wide x8'tall and its ~2.5" acrylic.

 

[Allseer12]

If I assume the center support column acts exactly like the rest of the window support area so it's basically 2 windows then acrylic thickness is 2.25 to 2.5 inches. If it was one continuous piece of acrylic (4x16ft) at 4.5ft water depth then the thickness is in the 2.5 to 3 inch range with normal safety factory (4).

Thanks again for the help! Went to a local Animal park today and stumbled upon this massive tank. 12ft Long and 4ft Tall, 3.5ft wide, they used a single sheet just shy of 1in thick acrylic. I'm fascinated by this setup to be honest lol. Certainly has me rethinking my design. Although they couldn't tell me where they got the Acrylic from ?

 

[Backfromthedead]

Thanks again for the help! Went to a local Animal park today and stumbled upon this massive tank. 12ft Long and 4ft Tall, 3.5ft wide, they used a single sheet just shy of 1in thick acrylic. I'm fascinated by this setup to be honest lol. Certainly has me rethinking my design. Although they couldn't tell me where they got the Acrylic from ?

View attachment 1500654

View attachment 1500655

Cool tank, that's probably the biggest red rainbow I've ever seen.

 

[M1A1]

Curved windows are cheating! You can get away with a lot thinner material since the curve acts like a bridge arch and really resists bending.

Everyone has a different safety factor (SF) when they design/engineer/build things. DIY stuff tends to be overbuilt (SF>3) in case of poor craftsmanship while professional stuff will go with the bare minimum SF because they know the quality of the materials and installation.

 

[fishdance]

Look towards concrete swimming pool builders for an acrylic panel. Large viewing panes are practically standard in swimming pools now and many builders buy - import in volume so you may be able to buy 100mm thick sheets cheaper than 50mm sheets from an acrylic reseller.

I wouldn't recommend having a foot of blind spot at the bottom as fish will choose to hide (they aren't stupid). Unless you are filling with deep substrate. Since your using concrete, I'd recommend sloped bottom to central drains, curved corners, water jets in walls to reduce your maintenance. Lighting for deep tanks can be tricky too.