Acrylic fabrication questions? I can help!
- Thread starter JohnL
- Start date
I've wondered about that as well. I've heard that the two varying expansion rates might ruin your acrylic for viewing purposes. But I defer to what they experts have to say.
What you're describing is exactly the way I do these tanks, and one of the few times I don't put the bottom under all the sides, (except for the bullnose itself)
The downsides are several; if there is warpage in the upper step -tank doesn't sit flat. If the upper step is at an angle, tank has problems. IMO the tank should be built first, then the stand should be made to fit the tank. Not the way most folks wish to go about it, but this is kinda special
The best way to do these is to make the entire tank 6' tall, then glue in the upper "L" then route the bottom out of it. More expensive - yes, but IME better in the long run.
IMO, given the size and design of the tank, you're pushing 1.5" .. I'd opt for thicker material or make changes to the design and/or size. JMO
There is a tank local to me that is similar in nature, though bigger, made from 7" acrylic and it cracked in exactly the spot one would expect
The owner went cheap on it and paid one firm to engineer it, one firm to build it, and one to install it. When it cracked, I was called in to access fault. I looked at the owner and said "you." If he had spent the extra $20k, one company would have done all 3 aspects. On a $500k tank, he screwed himself as all 3 aspects were done correctly according to all engineering and mfg standards. Basically, what I'm saying.. is be careful. It may be well worth the extra $5-10k or so to have it built professionally and get a warranty. There is a certain value to building this by one's self, but peace of mind is priceless.understood
reasonable enough
yup, there will, usually about 20%
shrinkage is usually more on the top than the bottom.
as much as possible IME
IMO yes, but opinions vary. If using 40, need a vacuum pump and/or centrifuge IME
some do, yes. It's a standard epoxy gun, but there are 2 or 3 sizes of these. If I remember, I'll get the model # off the gun, I've got a couple of them, see if there are any differences in manufacturer or anything, but both work well with the tubes.
James
Is there a way? yes, is it always the best thing to do? nope. What's the purpose and application? Expansion/contraction is not the issue I concern myself with on these things but rather any voids and the stresses induced on the material in the process. Plus the fact that you can pretty much count on it warping, but at times - just have to work it out
If you can give me some detail, might be able to point in a good direction
James
noobtothereef
New member
thanks for the replies james, i take it the centerfuge and or vaccuum pump is for removing the bubbles after the 40 is mixed? And for the gun, i have one that looks almost identical to it, but if i remember right, was about $50
ith usingthe 42 gun, does it work ery well casting seams like above? Is the tip small enough on it to "inject" the seam? Im also guessing the tips are the same mixing tips found on epoxy guns. If you do get an air bubble or two, can they be easily removed with a syringe?
On the stand, that was the game plan from the beginning, to make the tank first and the stand second, i will be making the stand in 2 pieces, one for the main tank and one for the step, they will be adjustable independantly in heights, the bolt holes will be obrounds for adjustablity. Will also have adjustable feet at multiple locations around the stand.
ith usingthe 42 gun, does it work ery well casting seams like above? Is the tip small enough on it to "inject" the seam? Im also guessing the tips are the same mixing tips found on epoxy guns. If you do get an air bubble or two, can they be easily removed with a syringe?
On the stand, that was the game plan from the beginning, to make the tank first and the stand second, i will be making the stand in 2 pieces, one for the main tank and one for the step, they will be adjustable independantly in heights, the bolt holes will be obrounds for adjustablity. Will also have adjustable feet at multiple locations around the stand.
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noobtothereef
New member
just curious, how big was that tank that has 7" acrylic? Id hate to have to buy a few sheets of that.........
yup, the pump/centrifuge is for removing bubbles from 40
IMO, no, the don't work very well at it. I squeeze out a bit to get rid of the first bubbles, then squeeze the 42 into a larger syringe and use that, or 1/8" vinyl hose on the syringes to inject the 42 where I want it. The syringe also gives a secondary place to float bubbles out
Never had to remove bubbles with a syringe, but I suppose its done. Squirt the 42 in there and gently push the pieces together a little bit.
In any case, be prepared to do some finish work... I've *never* seen such a joint come out that didn't require at least a few hours of finish work. The better you blend it - the more work it takes. Also keep in mind there may be up to 1/8" or so in thickness variation in the material. You can do your best to match pieces, but still will be a bit of finish work. Thickness tolerances on such sheets are somewhere in the neighborhood of +.060"/-.125" so a bit of variation is to be expected.
Fair enough
James
was like 24' long and 14' tall..btw, never fixed it, just patch it over a little, hid it, and called it good. As long as the load is static, it wasn't gonna move more. But if he ever emptied... bad news.
noobtothereef
New member
i am prepared for the finish work, i have seen the tolerences on the material thickness, thats crazy that it can vary that much. Im sure i will b able to blend it out, i have been painting cars for about 10 years in my spare time, i can work the sandpaper
James, I have another thread going but it's getting buried and I might as well add to this thread instead...
I was planning a 8'x1'x1' tank and I've decided to go to 8' x 16" wide x 14" tall instead.
What thickness of acrylic would you recommend? I don't think eurobracing is an option unless I go thin, maybe less than 3" but I don't mind cross braces. Maybe you could recommend a few options?
Thanks, Justin
I was planning a 8'x1'x1' tank and I've decided to go to 8' x 16" wide x 14" tall instead.
What thickness of acrylic would you recommend? I don't think eurobracing is an option unless I go thin, maybe less than 3" but I don't mind cross braces. Maybe you could recommend a few options?
Thanks, Justin
Hi Justin, I remember it
At the new dimensions, you have a lot more options. Personally, I'd use 1/2" with 2-3" euro-brace with a coupla cross-braces and call it good You could use thinner (3/8") material but may need to widen the bracing a little. Also 3/8" will bow a little more and since most people's big issue with acrylic is scratches - the thickness will help alleviate some of that. Thicker material = less bowing = scrapers slide flat on the material rather than the 2 outer points
Try to use a single sheet for the top with a larger radius in the corners of the top access cutouts - will help keep your tank from cracking at the top. You should be able to get top openings measuring ~11 x 24 or thereabouts - not bad for a long narrow tank
James
noobtothereef
New member
some more questions for you today james.
I have cut acrylic, thickest i have cut and routed is 3/4". On the 1.5", when going with the 45 degree casted seam method. I have a table saw and a large 10 1/4" circular saw, both with acrylic blades. I know i wont be able to feed the bullnose section through the table saw to cut the 45, so my only tool is the circular saw. I have a clampable straight edge for cutting. After cutting what would be the best way to prep the surface of this cut? I suppose i could build a "sled" for my router to hold it at a 45 but i dont think my 2" bit will be long enough. Could i prep it just by sanding it with a rigid block to keep it square? If so what would be the finished grit before casting with the wo 42?
I have cut acrylic, thickest i have cut and routed is 3/4". On the 1.5", when going with the 45 degree casted seam method. I have a table saw and a large 10 1/4" circular saw, both with acrylic blades. I know i wont be able to feed the bullnose section through the table saw to cut the 45, so my only tool is the circular saw. I have a clampable straight edge for cutting. After cutting what would be the best way to prep the surface of this cut? I suppose i could build a "sled" for my router to hold it at a 45 but i dont think my 2" bit will be long enough. Could i prep it just by sanding it with a rigid block to keep it square? If so what would be the finished grit before casting with the wo 42?
noobtothereef
New member
Actually it wouldnt cost me any more to do it this way, the 48"x96" sheet will be casted to the bullnose section, i can just make the "L" a little taller so that the 48x96 side sheet will hang over the "L" and then just route it off
noobtothereef
New member
IMO, given the size and design of the tank, you're pushing 1.5" .. I'd opt for thicker material or make changes to the design and/or size. JMO
Would it make much difference if i dropped the depth down by 6" overall? Where the main section would be 42" deep and the stepped section 66"?
Or maybe by 12" so its 36" and 60"? I really would like to go as tall as possible. I actually looked at tank yesterday thats located at Iowa pet foods and seascapes in des moines iowa, this tank is 1500 gallons and is 60"+ tall, just a basic large rectangle tank.
I like the look of a really deep tank, you can get more realistic dimensions with the aquascaping and not just a basic pile of rocks, thats the whole reasoning for the deep bullnose stepped section to have a "centerpiece" rockwork right at the end of the tank.
Hi Justin, I remember it
Thicker material = less bowing = scrapers slide flat on the material rather than the 2 outer points
Try to use a single sheet for the top with a larger radius in the corners of the top access cutouts - will help keep your tank from cracking at the top. You should be able to get top openings measuring ~11 x 24 or thereabouts - not bad for a long narrow tank
Awesome, thanks for the advice. I have a Sabic locally and this is what they have listed for cast acrylic products. Are any of these what I'm looking for?
Lucite® L Continuous Cast Acrylic Sheet
Patterned Cast Acrylic
Plexiglas® GM P-95
Polycast SAR
Thanks
James
You're asking someone how to do the prep work without the proper tooling. I use a router and jig, how someone does it any other way is not something I would know
But your proposed tank is much longer and under different stresses. No comparison IMO
James
None of it will apply. The SAR sheet *can* be used but I will never recommend anyone use it for aquaria. Other than that - it's all useless for your application IMO.
Only 2 materials I will recommend
Polycast (not SAR)
Plexi-Glas G
James
None of it will apply. The SAR sheet *can* be used but I will never recommend anyone use it for aquaria. Other than that - it's all useless for your application IMO.
Only 2 materials I will recommend
Polycast (not SAR)
Plexi-Glas G
James
Okay sweet. I'll see if they specifically carry either of those products. I only looked at the generic website.
Planning a tank for a friend and trying to determine proper thickness of acrylic. Tank dimensions would be 70"L x 48"D x 25"H. The tank will have an external overflow on the back and will have external wavebox on 1 end. Trying to minimize cross bracing if possible. What would be the correct material????
All things considered, I'd use 1" with ~5-6" perimeter flange and no cross-bracing required.
James
