Acrylic fabrication questions? I can help!

[CatsnClownfish]

Never mind to my last post. I've been reading on and I'll just read this whole thread. It's got so much great info. As a new tank builder, I really appreciate all the time people put into this (especially James and Floyd R Turbo). I'm learning about things I didn't even think of asking.

In reading, I discovered that I've already made a mistake in my current build. I have a 46"x17"x17" tank, all 1/2" acrylic including a top eurobrace and bottom. I have the four vertical walls assembled, but I haven't added the top or bottom. I used Weld-On 4 and the pin method. The seams look pretty good, though they have one or two bubbles each (I don't know how to remove bubbles yet). I'm also making a sump, which is done except for internal baffles.

Here's my problem: I thought the extra lip on the top and bottom piece, the part you use a router to remove, was optional. I don't have one. I'm worried that my tank won't have a fillet on the outside edge and so might leak.

Can I safely use my current top and bottom or do I need to get new ones cut with a lip on them?

Also, one more quick question: when putting camper foam down under the edge of a tank and then adding shims, do you put the foam parallel to the edge of the tank (so that the entire long end of a tank is touching the entire length of the foam) or do you put the boards with foam under the tank so that the foam is perpendicular to the long edge like you put in shims?

Thanks again.

 

[dcforester1]

Floyd what type double stick tape do you use? After you use it is it easy to get off the acrylic, or do you stick it to the paper on the acrylic? Thanks for the info


Derek

 

[Floyd R Turbo]

cat I might read your post tomorrow and reply, I'm beat today

DC I use Intertape 591 I believe, it is 1/2" wide. You can stick it to bare-on-bare acrylic and it holds extremely well. paper-on-paper holds very well also and that is what I typically do. Apply the tape to one side, then press it down (I run over it with a plastic spackling knife), peel off the paper coating, and press the other piece on to it.

Either way after you route it can sometimes be very hard to pry the pieces apart. This is where the trick comes in. Take the 2 piece and slam them down on a flat table and they pop apart

 

[CatsnClownfish]

Thanks, Floyd R Turbo. I could use your advice.

 

[Floyd R Turbo]

I'm also making a sump, which is done except for internal baffles.

I usually put the baffles in first - bond them to the same piece you first bond the ends to (front, for instance), then bond all of those to the other piece (back). Then bond euro, then bottom.

You can bond them in afterwards but it's difficult to use pins, you end up having to fit them in and use capillary action. Which is usually fine, it's just not as strong of a bond and outward bowing pressure might pop a seam one day. If you're worried you can add small gusset strips to strengthen the joint using WO #16

Here's my problem: I thought the extra lip on the top and bottom piece, the part you use a router to remove, was optional. I don't have one. I'm worried that my tank won't have a fillet on the outside edge and so might leak.

Can I safely use my current top and bottom or do I need to get new ones cut with a lip on them?

The fillet is there to prevent air from creeping into the joint as the solvent dries. So along the outside edge of the entire joint, you might end up with bubbles. This doesn't mean the tank will leak, a bubble would have to be big enough to span the entire joint to allow air through.

The result could be a weak joint. The bottom joint is under the highest pressure so this is the one that you want to be strong all the way around. If you get a few bubbles here and there, generally no big deal, as long as they are not super huge.

I'm trying to come up with a possible solution that would not involve cutting a new piece that is only 1/8" wider...all you need is 1/16" extra material all the way around (so 1/8" added to each dimension, if your front/back/side assembly is dead on square. Maybe that change things for you, maybe not.

However, I do have a super radical idea for you that may work. Just thought of this off the top of my head, may be too much work to be worth it but on paper it seems like it would do the trick.

Get some scrap strips of acrylic. They don't need to be thick or wide. Just 1/8" thick and 1/4" wide would be enough. Bond these to each edge all the way around, and it doesn't have to be pretty, and it can be extruded material. They can even be more than 1/2" wide but that makes it a little more difficult. Try to bond them so that the edge is flush with one side of the panel all the way around. You can use #16 for this or #3 or #4.

After they're all bonded on, let them cure for a couple hours. Then go around with a razor blade and scrape it down so that it's flush, preferably on both sides (which is why you want strips less than 1/2" if you can get them. You've basically extended the panel now.

Clean and prep the joint as you normally would, making sure the footprint of the tank is lined up with the footprint of the original panel, i.e. the strips are all outside of the envelope of the tank. Bond the panel in place, let it cure for 20+ hours, then flush trim. You essentially bonded on sacrificial material for the sole purpose of protecting the bottom joint by allowing a fillet to form.

I've never tried this before but trust me I'm an engineer, my job is to come up with solutions to problems that you never knew you had using methods that you can't understand. I stole that from a t-shirt. Forgive me I am really tired. But seriously today has been one of those days where I'm completely exhausted, yet I have come up with 3 knockout ideas on projects I am working on, go figure. This one above I have never thought of before but I'm willing to put money on it that it would work.

Also, one more quick question: when putting camper foam down under the edge of a tank and then adding shims, do you put the foam parallel to the edge of the tank (so that the entire long end of a tank is touching the entire length of the foam) or do you put the boards with foam under the tank so that the foam is perpendicular to the long edge like you put in shims?

Thanks again.

Either way works but I prefer parallel with the joint. But for the bottom and top joints, when you have a set of boards already made, run it parallel on the 2 long sides and then perpendicular on the 2 short sides. You'll be fine.

 

[adova]

Floyd what type double stick tape do you use? After you use it is it easy to get off the acrylic, or do you stick it to the paper on the acrylic? Thanks for the info


Derek

Not necessarily out of choice, I just used the 3M red double sided tape found in the paint department at Home Depot. I was going from paper to MDF. It held "ok" for the brief time that I needed it there and came off extremely easy. Not optimal, but works if you need it...

 

[dcforester1]

Thanks guys, do you need to do anything to clean the acrylic? or does the tape come off that easy?

Thanks Derek

 

[Floyd R Turbo]

Yes, you clean acrylic with Denatured Alcohol. Use this before you position the parts together for bonding or before you tape them together (if using bare acrylic), it removes any residue and oils (fingerprints). Do not use as a general everyday cleaner for your tank though, Brillianz for that.

Also use to remove tape residue, there is usually some but not always visible.

 

[dcforester1]

I would have thought that would hurt it. Thanks I am going by next week to get the right stuff. We have had so much snow here (Boston) I havnt had the time to get its

Thanks again

Derek

 

[Floyd R Turbo]

Nope, it leaves the surface free of all oils and that is what you want.

Now if you soak a rag in denatured and leave it sitting on a panel for the night, it will craze it. So generally you don't want to use denatured to clean, but you have to use it to get the oils off before bonding.

 

[Cbsailor11]

Floyd and others, Please review and comment on my proposed sump. All panels are 1/2" acrylic except the sock holder shelf is 3/8". Running volume is 12" of water(sketch is not to scale) Eurobrace is 2" wide, Do I need to go wider? Can I reduce baffle thickness to increase water volume? I see above where Floyd you have use 1/4" and 3/8" in some instances.

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[Cbsailor11]

 

[adova]

My impression is that you could probably go rimless if you wanted to - especially with the baffles bonded to the sides. I just assembled one with almost the exact same dimensions for height and depth but only 48" long from 1/2" - haven't decided if I am going to Eurobrace or not...

 

[adova]

Can I reduce baffle thickness to increase water volume?

Your water volume is not going to be affected much by changing thickness of the baffles, but if it is more cost effective, just use 1/4".

 

[Floyd R Turbo]

I agree you could probably go rimless because of the baffles. You can consider each section it's own separate tank so that will in effect reduce bowing. But then you also have to consider the worst-case scenario of a power outage. What I actually consider is an auto-top-off failure that drains your reservoir and then you get a power outage, but that assumes you have a limited ATO reservoir (like a 5g bucket) instead of a 55g Brute or something like that.

Also because of the baffles your euro does not really need to be what you would use for a typical DT - 1.5" is probably good, and you could use 1/4" for the euro also instead of 1/2" or even 3/8"

1/4" on the baffles is what I normally use, sometimes in the case of a pressure baffle I will go to 3/8".

 

[Cbsailor11]

adova, Floyd- Thank you both. I added the eurobrace due to the length. I will reduce all interior parts to 1/4" except for the initial sock wall in the drain down chamber and the fuge wall(3/8") Are these what you consider pressure baffles? This will also reduce material cost.
I need to do more math, I agree with Floyd's worst case scenario as I will have 15g barrel for the ATO. Would it be ok to increase to 20" high for more flood prevention still using 1/2" exterior walls?

 

[Floyd R Turbo]

Yes, you will be fine at 20" tall with 1/2" walls and a euro.

 

[Floyd R Turbo]

DC I use Intertape 591 I believe, it is 1/2" wide.

I actually use the 3/4" wide stuff, my mistake. Still 591 just 3/4".

I had promised a local school to build them a BA overflow box, finally got around to it

^^ thejuggernaut I took your "donut" idea and simplified it. Cutting a square is much easier than cutting a circle

For the internal box I made a few of these

to stick inside to keep the front face of the box from pushing in

 

[rickztahone]

Nice Floyd, what are the dimensions on the BA overflow boxes? Also, What kind of a bulkhead fitting do you use to mount these up? Do you just add an extra rubber washer in between?

 

[bmanzie]

Floyd what is your tricks for making the teeth so nice.