Acrylic fabrication questions? I can help!

[Floyd R Turbo]

If it were me, I would use 3/4" for a span that long, 1/2" might work but I would think that it would bow just a bit too much for peace of mind over the long term.

If you did just a 1.5" or 2" wide perimeter euro out of 1/4" (no crossbrace), you could go down to 3/8" wall material. Some might make the whole thing out of 1/4" at that point, but I prefer to use 3/8" minimum wall thickness for most things.

If you can get 3/4" cut to size without needing to buy a whole sheet, the cost is not going to be a huge difference.

 

[CuzzA]

Hey Floyd, my first and I believe successful attempt at creating anything from acrylic that will hold water. Still have to leak test it though. It's an ATO reservoir for my father in law's tank. Space is super tight in his stand so 19x5x19 are the external demensions. 1/4 inch cell cast acrylic welded with #4 with a 5 inch brace inside.

The questions I have 1) Are these bubbles anything to be concerned about? Pictured here is my first and worst seam. The others have very few bubbles. Likely due to being cut on a table saw. I now know a router is the way to go for perfection. 2) How would you recommend cleaning up the edges? My thoughts were to tape them off. Hand sand, wet sand (decreasing grit size) then maybe polishing it. Am I on the right track here? It is an ATO after all and doesn't need to be beautiful, just cleaned up. Could I use the same products I use on my fiberglass boat for gel coat? I'd rather not sink a bunch of extra money in compound, polish, pads, etc. for something no one sees, but I want it to look somewhat professional and finished.

Thanks.

 

[thejuggernaut]

Yea, I wouldn't worry with polishing. You will need around 4-6 different types of sandpaper, and they all run about $5-$7 a grit. Then you will need some compound. The Ultracut runs about $40 at O' Reilly's. If it is under the stand, I would be happy just flush cutting and using a small round over.

As far as the bubbles, it looks like it would hold water fine. Obviously any bubbles will reduce joint strength. How much, who knows. I can't tell from the pictures, is the top eurobraced?

 

[CuzzA]

That's what I'm thinking too. Just round off the edges slightly and wet sand smooth with products I already have and call it done. It is not euro braced, just a 5" vertical brace dead center toward the top. I figured this would be much stronger than euro bracing it. Similar to how overflow boxes are braced. Also, this won't be full 100% of the time. It's going on a 125 gallon glass cylinder, so I expect it to last a week before refilling. I would have liked it to be bigger, but the space in the stand is essentially 24x18 and the sump is a 20 high.

 

[adova]

Would a 24 x 24 x 18(h) rimless work with 1/2" or is 3/4" required? Every time I think I know the right answer I am wrong. I am guessing 3/4" but hoping 1/2"...

Shawn

 

[rfgonzo]

Would a 24 x 24 x 18(h) rimless work with 1/2" or is 3/4" required? Every time I think I know the right answer I am wrong. I am guessing 3/4" but hoping 1/2"...

Shawn

I would say 1'' for rimless at 18'' H

 

[rickztahone]

So what you do is start by bonding all the panels one at a time to the front panel. Order doesn't matter, it depends somewhat on baffle spacing. Up/downs are the toughest. More on that later

All baffles that touch the bottom panel need to be square and identical in relation to the other panels that also touch the bottom. If you can stack and tape and square them together, then mark one side as a reference so that side on all panels is facing the same direction, then if you're off-square you're OK because they're all equally off.

Now, you flip the entire assembly over on to the back panel. Bond one end panel and let it sit for a few hours. Right after you pull the pins and before the joint sets up, make sure that the other end panel lines up right, if not, then all the panels will be off.

After 2 hours, pin the next joint & set. Check last end panel alignment again. Wait 2 hours. Keep going until you have them all done.

If you have a set of up/downs that are 3 in a row with an inch or less between them, the middle one will be hard to get at. However the middle one is usually an 'up' baffle and has no pressure on it. So for this one, I pin it along with the next baffle and do them both at the same time. Or, if you can rig it up (usually by putting a 5lb weight on the top of the assembly) you can get all 3 baffles at the same time, but this can get tricky because #1 and #3 need to be flush with the bottom joint and lining up 2 of these at the same time can be problematic. So I usually do #1, and #2 together, or #2 and #3 together so I only have to line up one critical panel at a time. What you may find is that even with CNCd parts, things don't always want to line up dead-on because of variations in the thickness of the acrylic sheet (this is a known issue and not much you can do about it) which will cause a perpendicular bonded panel to line up differently (a few mm) depending on where you bond it.

Anyways, when you set a joint if it doesn't line up quite right then you essentially have to push it into position and hold it there for a few minutes until the solvent starts to set up, and in some situations, you need to use a large bar clamp to keep it there, even some shims in really bad lineups. I'll have to dig up a pic of one huge sump I did that I have to get creative on.

So once you get all the baffles in, they are all pin set joints and very solid. Then you scrape all the junctions on the bottom & top of the assembly to get rid of any lips, ridges, and solvent drips/finger smudges and bond the euro on, then the bottom, flush trim, done

You can use #16 if you have a bubble in a baffle joint that leaks (from one side of the baffle to the other) but this is pretty rare if you are able to pin the joints. For the 'up' baffle, this is generally not structural and so you can just wick it in afterwards if you want, but I would pin it on the first side so that you only have to do one joint this way (and put it on the back so no one sees it)

Floyd, i'm sorry to bring up one of your old quotes, but I am getting closer and closer to doing the baffles and I have read many suggestions here to make the baffles a little shorter so that they do not touch right up to the inner tank walls. With this being said, how are they welding these pieces to the tank wall if it isn't right up against it? Could you clear this up for me? Thanks.

This is my planned sump design:

 

[thejuggernaut]

Floyd, i'm sorry to bring up one of your old quotes, but I am getting closer and closer to doing the baffles and I have read many suggestions here to make the baffles a little shorter so that they do not touch right up to the inner tank walls. With this being said, how are they welding these pieces to the tank wall if it isn't right up against it? Could you clear this up for me? Thanks.

This is my planned sump design:
View attachment 316072

That is for people who silicone acrylic panels into a glass tank for a sump. The acrylic will expand when it soaks up water, and if they are wedged in there, will crack the glass tank. You need to route the baffles at the same time you do the sides, because they need to be EXACTLY the same. Not just in width, but also the angle. they don't have to be a perfect 90, but they all need to be the same. (Preferably you want them all to be at a 90)

 

[CatsnClownfish]

Yep, what thejuggernaut said: you want acrylic touching acrylic for baffles, but not acrylic snug against glass. The acrylic baffles can expand and break the glass.

 

[CatsnClownfish]

Would a 24 x 24 x 18(h) rimless work with 1/2" or is 3/4" required? Every time I think I know the right answer I am wrong. I am guessing 3/4" but hoping 1/2"...

Shawn

The calculator I normally use for acrylic thickness says that unbraced, you need at least .538" which means 1/2" acrylic, which is normally actually .472", is too small. 5/8" would apparently work.

But, I know there are manufacturers out there who sell tanks using thinner acrylic than that calculator calls for, so I'm not positive I know what the right answer really is. Personally, I follow that calculator and round up because a leaky or burst tank is such a big hassle.

 

[rickztahone]

That is for people who silicone acrylic panels into a glass tank for a sump. The acrylic will expand when it soaks up water, and if they are wedged in there, will crack the glass tank. You need to route the baffles at the same time you do the sides, because they need to be EXACTLY the same. Not just in width, but also the angle. they don't have to be a perfect 90, but they all need to be the same. (Preferably you want them all to be at a 90)

I'm sorry but I'm not understanding. Are you saying to cut all the acrylic baffles at the exact same time? I will be working with a table saw, not a router.

sry, I'm slow sometimes with stuff like this.

 

[CuzzA]

If this is a glass sump then you'll want to use glass baffles and silicone. If it's acrylic then use acrylic and solvent. Silicone doesn't adhere to acrylic and solvent doesn't work on glass. Using the right adhesive, designed for the right material will go along way and prevent a possible, sometimes inevitable failure, only to have to redo it. And when the tank is up and running this would be a big pain in the rear.

Also, I would reevaluate incorporating sponges and loose media. They're not necessary and will require extra maintenance.

 

[Gorgok]

I'm sorry but I'm not understanding. Are you saying to cut all the acrylic baffles at the exact same time? I will be working with a table saw, not a router.

sry, I'm slow sometimes with stuff like this.

Pretty sure he just means that once you setup the saw fence, run both the ends and baffles to that dimension, instead of doing them in different setups. While its not necessary if you are very meticulous, it does make it simpler to do it like that.

 

[thejuggernaut]

I'm sorry but I'm not understanding. Are you saying to cut all the acrylic baffles at the exact same time? I will be working with a table saw, not a router.

sry, I'm slow sometimes with stuff like this.

Normally, the parts are rough cut a little large on a table saw. Then using a straight cutter on a router table, you place a straight edge a distance from the cutter and run all of your acrylic pieces between the fence and the router bit. Because they are a set distance, the parts will be the exact same size. Then loosen one side, tap it a little closer, reclamp and run the acrylic through again on the opposite side.Normally a table saw doesn't create a smooth enough edge to weld. Look at page 169 starting at post 4218. I posted a few photos showing my table setup. It isn't perfect but it works really well. I think I may put a shiny piece of formica on it like Turbo has. I've made several projects already for people and the table already looks old. MDF doesn't wear very well.

 

[Floyd R Turbo]

Hey Floyd, my first and I believe successful attempt at creating anything from acrylic that will hold water. Still have to leak test it though. It's an ATO reservoir for my father in law's tank. Space is super tight in his stand so 19x5x19 are the external demensions. 1/4 inch cell cast acrylic welded with #4 with a 5 inch brace inside.

The questions I have 1) Are these bubbles anything to be concerned about? Pictured here is my first and worst seam. The others have very few bubbles. Likely due to being cut on a table saw. I now know a router is the way to go for perfection. 2) How would you recommend cleaning up the edges? My thoughts were to tape them off. Hand sand, wet sand (decreasing grit size) then maybe polishing it. Am I on the right track here? It is an ATO after all and doesn't need to be beautiful, just cleaned up. Could I use the same products I use on my fiberglass boat for gel coat? I'd rather not sink a bunch of extra money in compound, polish, pads, etc. for something no one sees, but I want it to look somewhat professional and finished.

Thanks.

You're not going to be able to sand down that lip...well, you will, but it will take forever and a day. You would want to flush trim that off with a router if you want it flush. Otherwise I would take a razor blade at a 45 degree to the edge, take 4-5 passes, and call it a day

Bubbles are not too bad but one thing to remember is that the basis for acrylic thickness requirements for a water vessel are not primarily based on the overall panel length/width or bracing involved, but rather the water column they are holding against. So you can't make a 48" tall tank that is only 2" wide out of 1/4" because it still has a 48" water column of pressure at the bottom joint. It could be 1" or 96", it's still 48" of water over it.

I think that your ATO vessel might be OK but I would fill it and leave it in the garage for a few weeks. As the acrylic absorbs water (16 week process) you will be able to tell if any of the joints are getting worse. Like you said it's not full all the time, but if it's going to fail, it'll be when it's full. At least that will be only FW though. If you want t feel safer, take some scrap material and bond it into the inside corner around the bottom with WO16, good to go.

 

[CuzzA]

Yes, I didn't even bother trying to get it flush. It's just an ATO. I did clean up all the edges with some wet sanding, compound and polish. It looks good enough for inside a stand. When I leak tested it, it held water, but had a slight bow under the brace so I added another one and now there is no bowing whatsoever. I think it should be good to go, but time will tell.

 

[rickztahone]

Floyd, sorry to keep bugging you with these questions.

I bought this blade off Amazon to cut some acrylic:
http://www.amazon.com/gp/product/B00LFCMTHY/ref=oh_aui_detailpage_o01_s01?ie=UTF8&psc=1
Turns out I bought it pre-maturely because although it fits on my table saw, I do not believe I will be able to make accurate cuts the way my table saw is set up. It is a cheap little one like this:

So, my next thought was to cut it with my skil saw circular saw. However, my skil saw only takes a 6" blade. I tried to get my hands on a skil saw that takes a 10" blade but have been unsuccessful. I don't mind taking the hit for the blade, it was $20, but I can't seem to find a blade similar to it in the 6" size for my skil saw. Would you happen to have any tips? The piece of acrylic I bought is 8ft x 15". It will be for my baffles, 5 of them, and my outer and inner bean animal overflow. I have everything ready to go but this.

Any help would be greatly appreciated.

 

[adova]

You are surely going to make more accurate cuts with a table saw vs. a circular handheld. Not sure what it is that has you making the statement, though. If it is due to a wobbly fence, just use something else that is straight such as a 1x3 or something.

 

[rickztahone]

You are surely going to make more accurate cuts with a table saw vs. a circular handheld. Not sure what it is that has you making the statement, though. If it is due to a wobbly fence, just use something else that is straight such as a 1x3 or something.

That table is just too small and the fence as you mentioned is not very stable. I wasn't going to try to free hand a cut though. I was going to follow a guide clamped down. I really would like to use the table saw, but to be honest, I don't really know how I would physically make it work. Plus the piece being 8ft long doesn't help, and I may need all of it. I will probably cut it down to half but I'd hate to cut somewhere and have me having to buy more down the line because of a sloppy cut.

 

[adova]

I hear ya - use the circular saw to get it to a manageable size and then finish on the table saw. Make sure you do not end up with a rough cut (read potentially uneven) on two sides or else you will not have a good reference side to use against the fence.

I would imagine that if you just cut in the middle (or near to it depending on dimension needs) that you would be able to manage ok.

Or, even better, take it to home depot and let them cut it on a sliding miter saw - just mark the cut points ahead of time...

Shawn