Acrylic fabrication questions? I can help!

[Acrylics]

Code Red, while crazing is bad, if it's simply superficial crazing - probably not a big deal. If you can feel it at all, I'd pass. Can you post a pic?

FWIW, if it is 72 x 24 x 30"H made from 3/4", that's at least the appropriate thickness

Seems like a real cheap price though, anything else wrong with it? cracked bracing or anything?

Hope it's just a good buy for you

James

 

[code_red63366]

I will pay them a visit today and take some pics and try to post them. As far as I can see there isnt anything wrong with it but then again being kinda new to this acrylic , I wouldnt know exactly what to look for other than what I have been briefly reading from other sources... Will get back with you james.

 

[110galreef]

in short what exactly is crazing, why is it caused?
stress? to much glue?

and if just superficial not to worry?

Also is crazing inevitable overtime??

 

[Acrylics]

in short what exactly is crazing,

in short; stress fractures in the material.

why is it caused?
stress?

yes

to much glue?

can be. Can be rapid heating and cooling from cutting, machining, polishing - usually flame polishing, but buffing too hard can also be a causative factor. Can be too much load on the material, can be using solvents on the material. Can even happen by adding Weld-on 16 or other solvent to an already glued joint.

and if just superficial not to worry?

generally speaking, yes, but superficial crazing can turn to a structural degradation of the molecular bonds, hence a breakdown in the material itself. So it's imperative to take care of your materials wisely.

Also is crazing inevitable overtime??

no, but is not uncommon.

Crazing is *usually* caused by introducing a solvent to a stressed area. Flame polished edges edges cleaned with solvents are the normal culprits. Windex, ammonia, alcohol, etc., on a flame polished edge can induce crazing. The severity depends on the molecular weight of the material and the cumulative stresses built up. Low molecular weight materials can't handle the stresses that higher mole wt materials can; ie., extruded material is low mole wt while cell cast are higher mole wt, and thus craze easier and much worse. This is why we generally recommend a good cell cast material over extruded materials.

And this is the *only* real difference between cast and extruded - the molecular weight. In every other aspect; physical, optical, and chemical properties of cast and extruded are either exactly the same or so minutely different that they're irrelevant. But molecular chain length determines how much stress acrylic can take, and it will never be listed on any property data sheet and most acrylic mfrs consider this info proprietary and won't tell you.

James

 

[110galreef]

great explanation!
Thanks

 

[code_red63366]

OK,, so here are the pictures... Sorry it took so long,, i had a hard time trying to upload them with my phone. After speaking with a pro in the area on the tank and sending him the pictures via text message, he told me that the crazing wasnt bad and that the tank was definitely worth a try. I payed 300.00 for it. it was made by a company that is local here(st. louis mo) called A.R.T. .. The owner stands behind his work and supplys the local salt water shops with there special tanks. oh and i was mis informed, the tank carries a 10 year warranty and it is only 2 years old,, so i have 8 years lefted on it...... I went ahead and bought it and brought it home,, now my next question is, what is the safest way of cleaning it? I have been told distelled vinegar warm water and a spray bottle..input?

 

[code_red63366]

hopefully it works this time?

 

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[Acrylics]

Code Red, nothing bad on that thing at all, good buy
Try just filling it with water from the garden hose first, even vinegar is a solvent (acetic acid) and though it may be safe to use, we'd rather avoid the use of solvents if we can.

If it's the same guy I'm thinkin' of, I know the builder, he used to be around here at RC. I like him, and we've talked a few times, he's a good man..

Great score
James

 

[code_red63366]

Code Red, nothing bad on that thing at all, good buy
Try just filling it with water from the garden hose first, even vinegar is a solvent (acetic acid) and though it may be safe to use, we'd rather avoid the use of solvents if we can.

If it's the same guy I'm thinkin' of, I know the builder, he used to be around here at RC. I like him, and we've talked a few times, he's a good man..

Great score
James

Thanks James! I believe they said his name was either Dave or mark,, cant remember now. I cleaned it up today,,,,filled it up and it held water fine......it just has alot of small scratches on it and a few big ones on the bottom, which im not worried that much about since the sand will be covering it,, so i guess the next step will be buffing/ getting the scratches out, which ever way is best to go about it,,,,,, i will have to do some more homework on that. All in all I am very pleased with it.

 

[fullmonti]

I'm going to build a temperate tank with 1" acrylic 15"x15"X20-22" tall ID. I have built small tanks/sumps but this will be the largest project so far not to mention the most costly. My first question is, do you think this tank would need any bracing around the top?
Then any suggestions or advice you may have to offer is welcome.

Thanks
Jim

 

[peppie]

I built a tank that is 33'' X 33'' X 13'' tall out of 1'' cell cast,and have less than 1/8'' bowing.
I think your tank size would be fine with no top bracing, It will bow a small amount, but nothing that I would be concerned with.
James will set me right, if I have mis spoke.

 

[Acrylics]

only real tip is spend the extra few bux and get good material; as always - Polycast or Plex G. And Peppie is spot on, don't need top bracing if you do your job right

For the bottom, can use thinner material and place a piece of foam underneath for the added insulation... or just use the 1"

Material shouldn't really cost much. Search around your local fab shops and find a fabricator that uses thicker materials... pieces that size are scrap around here so shouldn't be much different in other places. I'm usually happy just to recoup my expenses selling scrap pieces like that. Many shops consider this thick and heavy and get a little proud and it shows in their prices, but to others - just material.

James

 

[fullmonti]

Good deal, was hoping not to have to brace the top. I take it Polycast, Plex G & Peppie are types or brands of acrylic material? I'll have to check what type acrylic the local guy (only one I know of) quoted me is. What price should I expect, think he said about $25 sqft.

As for the bottom, The tank will have a center overflow. I want to have the normal two overflow pipes (1") & one 1" return, plus a smaller pipe to run electrical cords from the lights through so they wont be hanging off one side. All of those bulkheads wont fit in the 3 1/2" square (ID) overflow area. My plan is build/attach a well under the overflow so I can put the bulkheads on the sides of the well. So think it best to just go ahead & use the 1" on the bottom too.

The things I have built before I cut the pieces & run them over the joiner to get a clean edge, tape them together & run that thin clear solvent in the seems. I have never been around any one who really knows what their doing, I think the guy where I have been getting my acrylic told me that way a long time ago & seemed a good enough way to do it. Is that the best way or is there a better way? Haven't had any problems in the past but those projects where in the fish room & if they failed or didn't look good it didn't matter much. This tank will be in the living room so want to be sure I'm doing it right this time.

Thank you very much for your help
Jim

 

[Acrylics]

Good deal, was hoping not to have to brace the top. I take it Polycast, Plex G & Peppie are types or brands of acrylic material? I'll have to check what type acrylic the local guy (only one I know of) quoted me is. What price should I expect, think he said about $25 sqft.

Peppie was the first person to respond to your post, but yes - Polycast and Plexi-Glas G are the 2 brands of acrylic used in tank fabrication and IMO you should too.. $25/ft sounds about right for 1" nowadays.

The things I have built before I cut the pieces & run them over the joiner to get a clean edge, tape them together & run that thin clear solvent in the seems. I have never been around any one who really knows what their doing, I think the guy where I have been getting my acrylic told me that way a long time ago & seemed a good enough way to do it. Is that the best way or is there a better way?

Taping the pieces together is a rather poor way of building tanks, and simply not gonna fly for 1" material. Take a look at this thread - it's a good way for anyone to build their own using only stuff available from the plastic shop and a hardware store. http://reefcentral.com/forums/showthread.php?t=390652

Jointers are ok, but they won't square anything up nor will they all parts consistent in any fashion. But we can work with them if we have to..

Good luck and let us know if you have any questions

James