External Acrylic Overflow Question

[minibowmatt]

Im thinking about using an external OF on my 50G acrylic tank. The tank is made from 1/4" Acrylic, which is already a little thin. Im thinking if i cut a series of teeth into the back of the tank with a router and pattern, I whould not lose too much strength from the back panel? I cant do an internal or I would have to remove too much of the eurobracing. I could do a single elbow inside as my overflow (SpaceAce style) but I am worried that wont remove enough of the protiens off the top of the water.
I was offered another option, of using a second piece of Acrylic cemented around the hole to add more structural strength.. think of that piece as external vertical Eurobracing around the OF slot/teeth...

 

[Acrylics]

If you already think the material is too thin, I'd caution against this but...
Cut your slots in the back panel, when you glue the overflow box on - this will add some ridgity and help compensate for the material you remove by making the slots.

HTH,
James

 

[minibowmatt]

Thanx, James.
The overflow slot would only be about 7-8" long, with teeth. So I think i am going to do it. Any words of wisdom, on how I should make the cut? Should I make the teeth out of the original back wall, or cut a slot, and add teeth? Also How thick would you make the slot? I was thinking about using a 1/2 router bit to make the holes/slot?

 

[Acrylics]

Hi Matt,

The easiest would be to just cut a 7-8" slot at whatever height you want and add a screen, eggcrate, or comb filter afterwards. The height would be determined by how much waterflow you want through it, but as a general rule; a square inch will flow ~150-200gph via gravity so a 7" slot x 1.25-1.5"h will be good for ~1000gph +/- with no problem. By the same token, a 1/2" slot x 1"h will flow ~80-100gph and a 1/4" slot x 1"h will flow 35-40gph. This is probably a little conservative but I'm the type that would rather not have the water at the eurobrace but would rather have 1/4-1/2" airspace between the water surface and bracing but you can always valve the pump back a little.

Hope this makes sense,

James

 

[Anonymous]

If you are cutting the slots along the top there is bracing on right next to the top of the slots so there should be no bowing or anything there.

I think putting a strip of acrylic say 1/4" by 3/4" along the underside of the slots, at right angles to the tank would stiffen up the bottom of the slots . The water would just run over it and drop down into the overflow.

Just an idea, never tried it before...

 

[minibowmatt]

edit.. see next post.

 

[minibowmatt]

I made some test pieces today. I used the red to simulate the tank.
I cut 3/8"X 1 1/4" teeth with 1/2" space between each tooth. I also made a 1"X11" slot in the "tank" with a router. This should give me flow between 900-1200 GPH based on what James said earlier. If i glue the top and bottom of each tooth to the tank above and below the slot, It should replace some of the lost rigidity, not to mention I will have an overflow box cemented on there also.

Great! It looks like its gonna work out. I have one concern.. WIll the overflow teeth get clogged and cause a flood?
???
:?

 

[Anonymous]

That's a pretty big slot, unless you have a whole bunch of fishies die and float up against it, or have a mess of anenomies deside to take the plunge you should be fine...



Got a pic? I think that's a good idea to glue slots over the tank.

 

[Anonymous]

nevermind about the pic, it showed up

 

[Anonymous]

Looks good.

 

[minibowmatt]

thanx!