Acrylic tank build-design and questions.

[Backfromthedead]

Currently drawing up a plan for my first complete acrylic build which will start up sometime in the next few months. My latest rebuild of a broken acrylic tank into a sump went pretty well and ive been reading up, studying quite a bit to prepare myself but have a couple questions to help me get started.

So far nothing is set in stone but it will be something in the neighborhood of 72"Lx30"Wx48"H. I'll be using 1.25" acrylic for all the sides but im undecided about the top bracing and bottom layout at this time.

-is there any reason why the side panels can't overlap the front and back panels instead of the other way around (the traditional way)? I would rather do this for a few reasons. Mostly because it reduces the number of cuts i have to make drastically on my raw material.

-what are my other options besides acrylic for use on the bottom? Ive heard of people using hdpe, pvc among other things? How would i go about bonding a pvc sheet to acrylic? Would weldon 40 work there as well? How thick of a sheet would i need?

-for the top id like to go as minimal, as open as possible because im most likely making a custom canopy for the tank as well. I was thinking about just using a 1.25" acrylic slab to brace the middle and a thinner strip bracing the ends and corners.

Thanks for reading and for any advice ya mfkers.

 

[LBDave]

Please make 2.

 

[Backfromthedead]

Please make 2.

Ha so when the first ends up a dumpster fire I'll still have another shot! Great idea!

 

[Lepisosteus]

The side panels can overlap the front panels, depending on the method you use to assemble the tank it could make it more difficult. You could get away with 3/4” acrylic for the bottom and top brace. To save some $$$. I have no expierience bonding PVC but I have seen acrylic tanks with pvc bottom. I strongly recommend going with a full top brace. Even at 1.25” acrylic, that tank will have a noticeable bow.

 

[Backfromthedead]

The side panels can overlap the front panels, depending on the method you use to assemble the tank it could make it more difficult. You could get away with 3/4” acrylic for the bottom and top brace. To save some $$$. I have no expierience bonding PVC but I have seen acrylic tanks with pvc bottom. I strongly recommend going with a full top brace. Even at 1.25” acrylic, that tank will have a noticeable bow.

3/4" you say? I could probably splurge for the full top piece as well if its 3/4". As luck would have it i havent ordered material for the top and bottom yet.

My current plan is to make a wooden frame matching the inside dimensions and just build the tank around that. I was just gonna stand the long sides up to bond the first side wall then flip the whole thing to do the other.

I may have the option to go 1.5" thick on the acrylic for the long sides? Would it be worth the extra money?

Any other tips you can think of for a first time builder are greatly appreciated. Thanks.

 

[Ulu]

You can lap the corner in either direction, and you can lap the bottom with the sides in either direction, and it can change from the ends to the front and back.

You are solvent welding the acrylic, and in the end the tank becomes one solid piece, if the work is properly done. It would theoretically have the same strength as if you had cast the entire tank in a mold as one piece.

IMO You really want a generous continuous lip along the top of the front and back, in addition to a top brace from front to back ( & they can overlap.)

That will give you some real beam strength along the free edges, and prevent fracture at the critical corners of a lone top brace.

I would be surprised if you did not have some bow, regardless of which method you choose for bracing. That's a very deep tank. ~256 psf at the base joint.

 

[Backfromthedead]

You can lap the corner in either direction, and you can lap the bottom with the sides in either direction, and it can change from the ends to the front and back.

You are solvent welding the acrylic, and in the end the tank becomes one solid piece, if the work is properly done. It would theoretically have the same strength as if you had cast the entire tank in a mold as one piece.

IMO You really want a generous continuous lip along the top of the front and back, in addition to a top brace from front to back ( & they can overlap.)

That will give you some real beam strength along the free edges, and prevent fracture at the critical corners of a lone top brace.

I would be surprised if you did not have some bow, regardless of which method you choose for bracing. That's a very deep tank. ~256 psf at the base joint.

This is the way i figured it worked. But being a first timer, i was just playing it safe and making sure.

I always try to stay keen on good advice, and it looks like everyones voting for full top brace so thats the way i should do it i suppose. Wish i had a cnc mill to work the cutouts but I'll have to figure that out down the road i guess.

Everything ive read so far seems to indicate 1.25 is solid at that height and length. I could see an 8' or longer needing some thicker stuff for sure.

 

[Ulu]

If you can cut and sand the pieces accurately you can build the top up from parts and you won't need to make huge cutouts.

 

[Lepisosteus]

I had 3 tanks in the past of similar dimensions you are doing. One was 84x30x48” tall, the other two were 96x24x48” tall. The one 96” tank was made from 1.5” the other 1.25”. The 1.25” bowed a few inches from top to bottom. The 84” tank had a similar bow and was built with 1” sides, 1.25” front and back. All tanks used a 3/4” bottom and top continuous brace. They have been water tight for 10+ years now. Go with a full top.

Remember that once half that tank is built it will be around the same weight as a 300 gallon glass tank. Make sure you have lots of help.

If you do a solvent seam then the panels basically becomes one solid piece as mentioned. You mentioned the use of weldon 40 which is a two part polymerizing cement. This does not chemically bond the panels. Weldon 40 cures almost 3x stronger than a solvent seam but can be difficult to prep. A gap between panels or a 5 degree angle cut on the bonded edge is often required for ideal bonding. If not, much of the “cement” will be pushed out of the seam due to the weight of the panel.

Please do not “sand” the edges of the pieces. This will cause an uneven surface in the acrylic. Get the acrylic CNC router cut to the exact dimensions you want. The CNC cut edge will be ready for bonding without any edge prep (unless they have machine set incorrectly). Personally I pay $50/cut sheet of acrylic and it’s worth every penny.

I strongly suggest doing a practice tank first. Could be a lot of wasted money.

 

[Ulu]

. . . The 1.25” bowed a few inches from top to bottom. . . .

Woah!

How many?

I would not expect that much.