Acrylic fabrication questions? I can help!

[H20ENG]

If the joint was truly clear, then it would be as strong as the material, IME. How hard did you say you hit it?

I've seen hazy, downright cloudy, dry, bubbly, and "wavy" joints. All are weaker than a nice clear joint. Did you glue up dissimilar materials, like polycarbonate to acrylic perhaps?

 

[Bugs]

Not too sure the materials that is being used. I bought some scraps acrylic and build the sump with it. Well, I can definitely say the joint is clear and bubble free. I didn't really have to use a lot of strength to break the joint. Is it possible that I didn't give enough time for the Weld-on 4 to set before removing the pins? I don't know. I just want to make sure that the joint can withstand the stress and water pressure.

Just out of curiosity, has anyone build the tank using Weld-on 4 that last for a long period of time?

 

[troylee]

i built a tank like 5yrs ago with 3 and its still going....also my current display a 180gal with the same thing going on 2 yrs......most any tank uses solvents...james even mentioned the other day that the big boys do to for the bottom seam since the expansion of 40 and 42 can vary and make the bottom of the tank not flat...fwiw...

 

[Bugs]

Funny to say. I didn't have a problem with 4 edges (corners). It seems to stay in place very well. The only problem that I had was at the bottom. Do you think I should used Weldon 40 or 42 for the bottom instead?

 

[troylee]

hmm......james just mentioned the other day solvents are better for the bottom due to the fact when 40/42 cures it expands..hmm.....i wish i could really help you, but i think james would give you better advice on this, than i can since he has alot more exp. with it.........im using all solvents number 3 to be exact on my 300 gallon build just because of the stress tests i have done personally showed that solvents broke the acrylic around the weld vs. the seam breaking partially or completey with 40/42....now most of those test were done with 40......i just scrounged up enough like 2 months ago and invested in the 42 gun and glue which has been showing me better results and telling me i really need to mix the 40 to the exact specs. it calls out for to get the best results......but it is a pita. unless you actually weigh it out....im sure someone has called james to chime in on this already lol.....seems like when there is a technical question he mysteroiusly appears lol...........

 

[troylee]

oh ya i forgot to mention about what h20 said.....
if the seam is nice and clean and bubble free is a good indicator that the seam is well done like he mentioned but!!!! that is given you are using a good solvent to begin with i actully tryed out some of cyros new solvent acrifix and from the looks of the seam i was so excited it was bubble free, super clean, and no need for shimming and it was a rough saw cut on top of it.....i was like wow this is the best thing to happen in the plastic industry in along time, it was so user friendly and clean looking........then it sat for a week and i snapped it off real easy lol....looked great but really had no stregnth.....so pretty much the moral of the story is, if you are using a solvent thats amongst the top ones such as weldon or mcbond and get nice clean seams i wouldnt sweat the issue of a weak joint but others you might use and look good..... be carefull and test scraps first...

 

[Acrylics]

<a href=showthread.php?s=&postid=15048585#post15048585 target=_blank>Originally posted</a> by Bugs
Not too sure the materials that is being used. I bought some scraps acrylic and build the sump with it. Well, I can definitely say the joint is clear and bubble free. I didn't really have to use a lot of strength to break the joint. Is it possible that I didn't give enough time for the Weld-on 4 to set before removing the pins? I don't know. I just want to make sure that the joint can withstand the stress and water pressure.

Just out of curiosity, has anyone build the tank using Weld-on 4 that last for a long period of time?

Weld-On 40/42 or "cast" joints can be stronger than solvent bonded joints if done right, with the right materials but if the whole thing isn't done correctly - no advantage and can be worse.

Solvent bonded joints done with the right materials are plenty strong, to the point that we will never see in common tanks. I mean, IPS claims the joint strength of solvent bonded joints is 2700psi - we will never see than kind of pressure on the joints in a common tank so using something that "claims" far stronger (with caveats) seems superfluous to me.

I don't personally use Weld-on 3 or 4 but most tanks built are using these and they do last many years. We've got tanks in public aquariums that were built using solvents that are still in service after 20 years and those tanks will be filled/emptied multiple times in multiple locations. That said, I don't dissuade folks from using 40/42 as it definitely has it's place, just know that it won't *necessarily* be stronger/better.

"Soak time" affecting joint strength can be debatable. On one hand you want to get the cleanest joint possible so you'd think that the longer the soak time - the better. OTOH this stresses the material more as the solvents are chemical stressors and doing this also puts more acrylic into solution in the joint so requires much more time to fully cure. Hence, I don't really care for the longer soak times, to me - 30 seconds is plenty of time.

To me, the method of sticking the pieces together is not the critical thing here but rather the material used and the material preparation. If the joints snap, ever, it's generally not the fault of the method you used but more likely the material, material preparation, or technique in using them. Practice for a bit using both, see what you're most comfortable with, using quality materials but both methods are plenty strong for all of our applications.

Hope this makes sense, it's still early

HTH,
James

 

[troylee]

after reading the last couple pages of this thread bugs......i see you said in a previous post that you picked up some extruded and cast material to build a sump......with that being said here is a good reason why that happened to you.......if you bond extruded to cast material with solvents the extruded breaks down alot faster than the cell cast material and your joints might have looked good but on one hand the joint was not so strong being that the extruded broke down and gave you a good looking joint but was very weak to begin with.......if that makes sense..lol......gluing extruded to cell cast is vey tricky for this reason because of the 2 different materials and 2 different reaction times......i use extruded all the time at work and the solvents break down the material so fast you really dont need a waiting time vs. a good 30 to 45 seconds on cell cast....hth.

 

[troylee]

bugs,
here is a simple and effective way of testing your joint's...and it will tell if your material and solvent/glue is good as well....
simply glue 2 pieces together at a 90 and let them sit a day or so in this case it was only 18hrs because i wanted to show you this..... i glued them after reading your post yesterday....the material is 3/4" plexiglass "g" and i used weldon 3 solvent....once they have cured for at least 24hrs,i would say put some saftey glasses on, and lay the piece on a table or floor and smack the top edge of the acrylic with a hammer untill the pieces seperate....once that is accomplished the acrylic should break around the weld leaving some material on both sides as seen in my pictures this is a good strong weld...

 

[Bugs]

James,

Thanks for the info. I will give it a test drive on both Weldon 40 and 4. If Weldon 4 works well with cast acrylic, I will definitely go with that as I feel a lot more comfortable with it. By any chance, can you show me the method using Weldon 40?

 

[Bugs]

Troylee,

That is a good test. I will try that. Today I will pick up the precut acrylic. I will give it a test before I actually build the tank. At least I can feel at peace when it completes. BTW, thanks a lot for you input. I will post the result after it is completed.

 

[troylee]

do you enjoy scraping, sanding, and polishing for hours on end????if not i wouldnt reccomend the 40.........it's more hassle than it's worth on 1/2" thick material.....

 

[Bugs]

I don't enjoy it. Do I have a volunteer?

 

[troylee]

i hear ya lol!!!!!!!!

 

[Bugs]

Ok....I have a question. I found the pix in this thread and I am curious. Where can I buy the grey strip and what does it call from the picture below? Thanks.

 

[Bugs]

I am building a reef tank with 1/2" thick acrylic. The tank size is 78" x 30" x 24". I want to have the euro brace around the tank to be as small as possible. Currently, my plan is 5.5" euro brace around the tank and the center brace is 6". Is this sufficient enough? Can I go smaller? Any help is appreciated.

 

[TAB]

<a href=showthread.php?s=&postid=15062190#post15062190 target=_blank>Originally posted</a> by Bugs
I am building a reef tank with 1/2" thick acrylic. The tank size is 78" x 30" x 24". I want to have the euro brace around the tank to be as small as possible. Currently, my plan is 5.5" euro brace around the tank and the center brace is 6". Is this sufficient enough? Can I go smaller? Any help is appreciated.

half inch is just to thin for a tank that size. even 3/4" is pushing it.

cyro( makers of arclite GP and other products) has a spread sheet that you can dl, its strickly for aquariums.

you can find it here http://www.regalplastics.net/aquarium.htm


you do need excel to open it.

 

[troylee]

ya bugs your gonna need to step up the thickness there bud.....i remember you saying a 200gal not a 250gal not that it really matters about how many gallons to deterimne a thickness.....but my current display is a 180gal with 1/2" and i have no problems with bowing etc.but the tank measures 18w24t84L........i wouldnt reccomend anything less than 3/4" thats what im building my current tank out of and i went to james "acrylics" for the same question on the eurobrace since he has a ton more of exp, building aquariums than me and i wanted the most open top i could have and he told me to go with a 3.5" euro brace with two 6" center braces which yeilded me 3 openings of 26"x16" on my tank you can check my thread lets build the ultimate 500gal reef tank for more info and pics it should be alot of help to you.........its on the first or second page here in this forum.......i have personally seen 300gal tanks from atm. that are 30tx24wx96L and they were constructed from 3/4" so that was kind of a lead way and using james inteligence to back it......hth.

 

[crab0000]

I am going to try to build a sump 18"WX30"LX14"H. Would 1/4" be thick enough? If so what size lip would I need around the top? Thanks!

 

[troylee]

given you put a decent amount of baffles in the sump to seperate everything and help with bubble control it will support the sump nicley .....i would yes 1/4" is sufficeant......i would run like a 1.5" to 2" brace around the top if possible.....and use a cell cast material if possible.......hth...