Acrylic tank build-design and questions.

[Backfromthedead]

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.

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Appreciate the advice. I had considered a test run but dont really have a use for any other tanks or the money for extra material at this time. I believe the sheets i am buying are milled smooth already, but if theyre not i suppose i will have to find a machine shop.

Would that 5 degree fillet cut be all the way through the sheet or just partially? How thick should the gap be? Couple millimeters?

 

[Lepisosteus]

Appreciate the advice. I had considered a test run but dont really have a use for any other tanks or the money for extra material at this time. I believe the sheets i am buying are milled smooth already, but if theyre not i suppose i will have to find a machine shop.

Would that 5 degree fillet cut be all the way through the sheet or just partially? How thick should the gap be? Couple millimeters?

The fillet cut is only on the bonding edge. If you make that type of cut there’s no need for a gap as it provides the gap. Bond the “gap” side of the angle to the inside of the aquarium.

 

[Lepisosteus]

Woah!

How many?

I would not expect that much.

From top to middle and bottom to middle with a level held vertically and level in the middle, there was roughly a 3-4” difference

 

[Backfromthedead]

From top to middle and bottom to middle with a level held vertically and level in the middle, there was roughly a 3-4” difference

Holy dingus thats damn near a bowfront.

 

[Backfromthedead]

The fillet cut is only on the bonding edge. If you make that type of cut there’s no need for a gap as it provides the gap. Bond the “gap” side of the angle to the inside of the aquarium.

Right sorry i meant to ask if i went with the gap method instead of the angled cut how thick should i make the gap?

 

[Ulu]

The gap depends on the glue. Read the instructions.

With regular solvent welding the glue is simply the thinest solvent, and goes into the thinnest possible gap one can ordinarily make, by capillary action.

The least solvent you use the faster it works, because the solvent must evaporate for the joint to harden.

I've never used Weldon #40 or similar on plexiglas, but they can fill a tiny gap.

If you have gaps your joints may be too loose to solvent weld, and you will know when you apply the solvent. It won't fill the gap and you'll see white spots in the seam.

 

[Lepisosteus]

Right sorry i meant to ask if i went with the gap method instead of the angled cut how thick should i make the gap?

Around 1/16” to 1/8” for weldon 40. For any methylene chloride based solvent, 28 gauge wire has worked the best for me.

 

[Lepisosteus]

The gap depends on the glue. Read the instructions.

With regular solvent welding the glue is simply the thinest solvent, and goes into the thinnest possible gap one can ordinarily make, by capillary action.

The least solvent you use the faster it works, because the solvent must evaporate for the joint to harden.

I've never used Weldon #40 or similar on plexiglas, but they can fill a tiny gap.

If you have gaps your joints may be too loose to solvent weld, and you will know when you apply the solvent. It won't fill the gap and you'll see white spots in the seam.

Have you built an acrylic tank?

 

[Ulu]

Have you built an acrylic tank?

Nothing bigger than a breadbox. Just overflows and a filtration box. Our school first shop project back in 1967 was building stuff from plexiglas. It's not mysterious. The joints must be thin and neat and they must wet out thoroughly.

. . . 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 can't imagine getting anything CNC cut here in California for $50 unless you're buying a lot of plastic. That would certainly be the best way.

Sanding and scraping is not the preferred method, but sometimes I have no choice. Depends on how good I am with the saw.

CNC was just coming to be when I started college in '72. My first programming job was with an early IBM systems 32 based CNC system with paper tape. Anyhow this work was all done before CNC was available too. Panel saws, sanding blocks and scrapers.

 

[Ulu]

Around 1/16” to 1/8” for weldon 40. For any methylene chloride based solvent, 28 gauge wire has worked the best for me.

I can no longer find methylene chloride in California. I've been using MEK which is still available. I have no idea if that would be suitable for a big tank. Might cause crazing.