Acrylic Fabrication Q & A

[Turbo's Aquatics]

DIY king acrylic aquarium builds and was under the impression that was the best method of assembly

With all due respect to him, because he does have some great advice...I would not follow his advice on tank assembly, at least not the version where he welds seams while they are vertical using capillary action and tape. This method 10,000%, without a doubt, proven over and over again, produces weaker joints compared to the pins & shims method. There is absolutely zero question about this. It's physically impossible to make a vertical seam capillary weld stronger than a pins-method weld.

Also, James @acrylics reportedly took him out to the woodshed one time over his method/advice a while back. I don't recall reading the discussion but I hear it was epic. Yet, he did not change his advice. I have seen videos of him using the pins method, but I've seen others who say they learned everything from him, and they are building 180g+ tanks using that method. To me, that is absolutely absurd.

So, there have been several posts within this thread that state DIY king's aquarium acrylic calculator is inaccurate and then several posts later individuals link an Excel spreadsheet that is allegedly more accurate

I'd have to search to find the post you're referring to.

Here's a simple guideline, thanks to @acrylics (and I hope you don't mind me sharing this)

Eurobrace: Start with 3" one-piece perimeter eurobrace on any tank

Inside corners: minimum 1.5" radius (3" diameter circle) on all cutouts

Material Thickness*:
24" high, use 1/2" minimum
30" high, use 3/4" minimum
36" high, use 1" minimum

* Note: these are imperial thicknesses, i.e. 1/2" = 0.500" versus the "metric equivalent" which is 1/2" = 0.472"

Crossbraces: 6" wide crossbrace every 24" of tank length.

- So a 48 x 24" will have 3" perimeter eurobrace and a 6" crossbrace.
- If the same tank were 72" long - just one more crossbrace.
- At 8' length, I recommend jumping up one material thickness to keep deflection down.

Eurobrace tweaks:
There are times when someone's lighting scheme doesn't match the above formula. i.e. if someone wants an 8' tank but only 3 cutouts in the top. In such cases, increase the eurobrace width to 4.5" and increasing the width of the crossbraces to 8".

If someone doesn't want the crossbrace - they simply have to make the material thicker, and/or increase the width of eurobrace to maintain rigidity.

So with that being said:

72 inches long x 16 inches high would require less 1/2 inch acrylic ( 0.430 inches)

That's 11mm acrylic, the metric-equivalent of 1/2" is 0.472 or 12mm. However, for a 16" tall tank, 11mm would probably be OK. 12mm would be better. It's not a matter of will it be strong enough, it's a matter of how much it will bow. 3/4" will bow less, which means less chance of a cleaner magnet/pad not making contact, requiring more passes to remove any algae, meaning more propensity to scratch.

My ideal dimensions would be 72 x 16 x 20 with additional acrylic to be purchased for the bracing

If your ODs are 72 L x 16 H x 20 D and your thickness is exactly 0.500" (for simplicity, and for the math below) then your finished panel sizes would be (assuming you are adding overage for fillet and flush cut):

72.25" L x 15" H front and back
15" H x 19" D left and right
72.25" L x 20.25" D top and bottom

For example, the vertical 16" is the 15" panel + the two 1/2" panels bonded on top/bottom = 20"

Note: "finished" means after any squaring and edge prep via a router = pieces all ready for assembly, not the rough-cut dims.

Also note: if you use 0.472" then you have to factor that in for the front/back/left/right dims if you want the tank to come out exactly 72x16x20. If you don't, and you cut to the dims above, your actual tank will be 72 x 15.944 x 19.944. So in other words, if you're super duper uber picky, account for that difference.

 

[acrylics]

Wow new to this forum, a ton of useful information in here. I've been watching a ton of DIY king acrylic aquarium builds and was under the impression that was the best method of assembly. Nearly jumped into making a tank. So, there have been several posts within this thread that state DIY king's aquarium acrylic calculator is inaccurate and then several posts later individuals link an Excel spreadsheet that is allegedly more accurate. However, it seems that both calculators are based upon a formula made by a company named CYRO. Seems to be a bit of conflicting information, can anyone clear this up for me? Anyways, by using this calculator it appears that a tank 72 inches long x 16 inches high would require less 1/2 inch acrylic ( 0.430 inches). I am dubious of this calculation.

It depends entirely on how you brace it, which is just one of the issues I have with the Cyro calculator. At any rate, 1/2" would be just fine for the 72 x 16" high tank, provided you had a 2.5" wide perimeter flange (AKA euro-brace) and cross-bracing every 24". This would yield you 3 top openings, each measuring ~15 x 18+" based on the 72 x 20" wide footprint. If you did that, then 1/2" would be fine and you'd have minimal deflection - almost undetectable. Another option is 2 top openings which would require just a single top brace. I'd probably look at ~30" long x 14" or thereabouts. Almost any time you eliminate a cross-brace, you have to increase the width of the perimeter flange to make up for the loss of rigidity/strength.
If you can handle that much bracing, then yes - thicker material would be required.

A local company provides a sheet of cell cast acrylic 1/2 inch at 5 feet x 8 feet for $494 Canadian Rupees, I would like to optimize these dimensions of course. My ideal dimensions would be 72 x 16 x 20 with additional acrylic to be purchased for the bracing. Would this be an unwise thing to do? Should I just go with a 3/4 inch acrylic at 600~ ish Canadian Rupees just to be safe?

You could get everything out of (1) 5x8 and you'd need one more piece to make one of the long panes, either a side or top/bottom. If you're wanting to optimize yield, your tank would be ~72 x 20 x 20" with again - everything coming out of a single sheet sans one lang pane.
What brand of material are you looking at? most don't glue well for our needs..

HTH,
James

 

[WiredWeasel]

Thank you both for such comprehensive answers. I really appreciate all the help. After considering your concerns and criticisms regarding my plan, I think Im going to go with a smaller foot print tank 60x20x20 and increase the thickness of the tank to 3/4. I think this footprint is better for the space I have in mind for the tank. The 6 foot would be slightly cramped I think. In regards to bracing, I honestly have no problem with an enormous brace that takes up space. I'd prefer the peace of mind that my tank is safe and has minimal deflection/bowing.

As for the brands, most of the local companies here carry polycast, arkema and Acrylite-GP with the red font.

I am hoping to get the polycast, but it seems that 1/2 and 3/4 is not in stock at any of the local suppliers at the moment. So the build may be stalled for awhile.

I dabble into a lot of "fine woodworking" so I have a router, jointer and all that good stuff. So I think I will joint the edges for the seams and then additionayl scrape the seams.

 

[imustbenuts]

Hey acrylic gurus. My DIY sump has been in service for about a year. I just pulled it to clean it and decided to do a once over to see how it’s holding up. Curious if this is a problem and do I need to reinforce it. It is on the bottom seam.

 

[Turbo's Aquatics]

I would say so. But I’ve seen tank with this separation worse than this and they’re still holding. One LFS has a 600 with a 10” section like this one bottom front seam and I about #2 a brick every time I see it....

 

[imustbenuts]

About #2 a brick?

 

[Smo]

About #2 a brick?

I believe it is a technical term used by acrylic fabricators when they see a problematic joint defect. Although I could be wrong...

 

[Turbo's Aquatics]

How about "I about have an unanticipated bowel movement"

 

[don_chuwish]

LOL. Sudden Involuntary Rectal Masonry Excretion

 

[imustbenuts]

How about "I about have an unanticipated bowel movement"

Hahaha. I admit it was late when I read your response. Now I see what you were saying. Lol I though it was a special solvent and acrylic your were using for repairs.

 

[imustbenuts]

@Floyd R Turbo what size acrylic should be used to make the patch? Should I patch all the way around the perimeter or just where the spots are forming? Thanks for the assistance.

 

[Turbo's Aquatics]

Gusset on the inside along the length of the seam would be good. Is it just that one spot along the edge, or is there something else going on near the corner too? I can see what looks like 2 lines there also.

 

[imustbenuts]

Yes, there are small lines in that corner and other small spots forming. Nothing really major but I’d rather be safe than sorry. What size gusset do you recommend?

 

[imustbenuts]

Gusset on the inside along the length of the seam would be good. Is it just that one spot along the edge, or is there something else going on near the corner too? I can see what looks like 2 lines there also.

@Floyd R Turbo would 3/8 x 3/8 square stock be good as gussets or could I just cut 1/4” strips off of 1/4” sheets. Which would be best?

 

[Turbo's Aquatics]

I would say, the thicker the better. Also remember there is usually a fillet on the inner corner, so you will want to chamfer or round off the gusset so it makes contact on both panels. What were you planning to use for solvent?

Gussets can be bonded in with #4 or #16, it's one of the places where #16 comes in handy. You can use #40 but then you don't want the gusset to sit completely flush as that will create a dry joint - it's intended to fill a gap, but you also want a gap to fill actually

 

[imustbenuts]

I would say, the thicker the better. Also remember there is usually a fillet on the inner corner, so you will want to chamfer or round off the gusset so it makes contact on both panels. What were you planning to use for solvent?

Gussets can be bonded in with #4 or #16, it's one of the places where #16 comes in handy. You can use #40 but then you don't want the gusset to sit completely flush as that will create a dry joint - it's intended to fill a gap, but you also want a gap to fill actually

I was planning to use #4. I have 16 as well. I hope it goes well.

 

[cromag27]

I would say, the thicker the better. Also remember there is usually a fillet on the inner corner, so you will want to chamfer or round off the gusset so it makes contact on both panels. What were you planning to use for solvent?

Gussets can be bonded in with #4 or #16, it's one of the places where #16 comes in handy. You can use #40 but then you don't want the gusset to sit completely flush as that will create a dry joint - it's intended to fill a gap, but you also want a gap to fill actually

16!! ;Jawdrop

 

[cromag27]

no jointer and no scraping. you won’t like the results.

I am hoping to get the polycast, but it seems that 1/2 and 3/4 is not in stock at any of the local suppliers at the moment. So the build may be stalled for awhile.

I dabble into a lot of "fine woodworking" so I have a router, jointer and all that good stuff. So I think I will joint the edges for the seams and then additionayl scrape the seams.

 

[WiredWeasel]

no jointer and no scraping. you won’t like the results.

So just use the router to clean up the edges and apply weld-on?

 

[Turbo's Aquatics]

What @cromag27 was saying is that scraping the edges (manually) will tend to cause rounding and allow air intrusion when the solvent evaporates. You want razor-sharp prepped edges.

Related to the jointer, this is "OK" but not perfect. The reason is that you need opposing edges to be perfectly parallel and/or square as well as identical.

Further:

The ends are bonded on all 4 sides. So these have to be (ideally) perfectly square or (at minimum) identical and have 2 sets of parallel edges (such that the top & bottom are parallel, and the front & back are parallel). If you have a slight "parallelogram" angle to them, it has to be really slight (like, thousandths of an inch when you flip one over and place it on top of the other). This is really easy to induce when using a jointer to finish prep edges

the front/back are bonded on the top and bottom (the ends are bonded to the front/back, so the left/right ends of the front/back pieces are fodder for flush trimming and don't really matter). But the top/bottom edges of the front/back pieces must be parallel. Again, you don't want to induce a non-parallel with a jointer, this will cause you a huge headache after you bond the 4 pieces together.

The reason to use a fence and router on a table and pass the pieces between the fence and the table vs the standard of using a fence behind the router (essentially same as a jointer) is to make dimensions equal and perfectly parallel.

So you make your ends square (using a jig or whatever technique you want) and then as you do your edge prep, the last pass should be all 4 pieces with the same fence setting so that your "height" dim is the same on all 4 pieces. Then same thing with your ends on the "depth" dim. I usually leave the ends double-stick-taped together from rough-cut to weld-ready to make this easy.