Acrylic fabrication questions? I can help!

camaroboy8691 said:
is arkema cast gen pm2 a good material ? the plastic supplier i found says thats what all his aquarium builders use .... any info on this stuff ?
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Arkema is the manufacturer of Plexi-Glas, "gen" usually means general purpose, and pm2 is just paper masked on both sides. It doesn't say anything about what the material *is*.. Arkema makes several cast materials; the 2 that we are interested in are call Plexi-Glas G and P-Max. Plexi-Glas G is the good stuff and will be plain paper masking on one side and the other side will have "Plexi-Glas G" written all over it in blue. P-Max is the cheap stuff; will be plain paper masking on both sides, zero quality control, zero inspections, zero tolerances, may include lots of inclusions in the material, and zero warranties. If you choose to use this material - that's fine, but I wouldn't and wouldn't recommend it for anything other than a sump or something that will never be seen.

IMO you need to ask them a be absolutely clear that it *has* to be actual Plexi-Glas G and have that written on one side from the factory. Most plastic salesmen don't know anything about the differences between the materials.

As for his aquarium builders... ugh - meaningless in and of itself.

HTH,
James
 
hi james ,

i know what you mean about what his customers use VS what i am using ... i own a metal fab shop and wont settle for anything but the best for my customers . no foreign stainless , etc ... just didnt know what i got and figured id ask .

my sales rep replied back to my email with good info about what i have vs what i need to buy yet , basically saying what you said , the non printed stuff i have is the PMAX .

my next question , can the Pmax be bonded to the plex-g ? i already have these 2 sheets of the PM2 and would hate to see them go to waste .... so im wondering can i just use those for the top and bottom of my project instead of buying the 3/4 material ? and ill just buy the plex-g for the sides ?

thanks
 
camaroboy8691 said:
my next question , can the Pmax be bonded to the plex-g ? i already have these 2 sheets of the PM2 and would hate to see them go to waste .... so im wondering can i just use those for the top and bottom of my project instead of buying the 3/4 material ? and ill just buy the plex-g for the sides ?
Click to expand...
Absolutely, sounds like a great use of the material :)

James
 
if they have a 5x8' of Plex G, might be a cheaper way to go? unless you want to use 1" for the sump :)

Looking forward to pics :)

James
 
if they have a 5x8' of Plex G, might be a cheaper way to go? unless you want to use 1" for the sump :)

Looking forward to pics :)

James
 
Acrylics said:
Build both tanks sometime... the rimless tank will scare you with the amount of deflection, and the tank with a brace will have near zero deflection if eurobraced and crossbraced.. but the formula doesn't say a damned thing about either of those things.

nope, even with 3/4" - it'll bow badly unless there is crossbracing. But again, nothing in the formula about that.

James
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Hey James, I'm curious in your professional opinion how much you think this configuration would bow? I have built many many tanks, but not really many rimless ones so can't really speak from experience on their bowing/deflection in comparison to properly braced tanks aside from in theory. At 48" length I would certainly figure this tank would be just fine rimless at 3/4" material wouldnt it? With a total height of only 12", minus 3/4" for the bottom and 1" for water level it would likely end up with an actual water level of about 10". In your experience what do you think would be the level of bowing at 48" length and at the mentioned 72" length?
 
Oh, I didn't see the 12" deep factor, I was thinking 72 x 24 x 24. That changes everything. My bad. However it made for a good discussion LOL
 
adambowersva said:
Hey James, I'm curious in your professional opinion how much you think this configuration would bow? I have built many many tanks, but not really many rimless ones so can't really speak from experience on their bowing/deflection in comparison to properly braced tanks aside from in theory. At 48" length I would certainly figure this tank would be just fine rimless at 3/4" material wouldnt it? With a total height of only 12", minus 3/4" for the bottom and 1" for water level it would likely end up with an actual water level of about 10". In your experience what do you think would be the level of bowing at 48" length and at the mentioned 72" length?
Click to expand...

48" span at 15" high bows ~5/8" and 72" span at 12" height bows nearly an inch. This is not total deflection including both sides, but 5/8" and 1" deflection per side.. both of these from personal experience.

48" span at 12" height would probably bow 1/4" - 3/8" as an educated guess. Remember, tanks will bow less at start-up that at ~14 weeks when the material has reached it's saturation point.

James
 
Floyd R Turbo said:
Oh, I didn't see the 12" deep factor, I was thinking 72 x 24 x 24. That changes everything. My bad. However it made for a good discussion LOL
Click to expand...

Lol, yeah I wondered if you were missing that part ;).

Acrylics said:
48" span at 15" high bows ~5/8" and 72" span at 12" height bows nearly an inch. This is not total deflection including both sides, but 5/8" and 1" deflection per side.. both of these from personal experience.

48" span at 12" height would probably bow 1/4" - 3/8" as an educated guess. Remember, tanks will bow less at start-up that at ~14 weeks when the material has reached it's saturation point.

James
Click to expand...

Wow, that is more than I would have expected for a 72" long tank with 10" of water. 1" each side is certainly outside my "comfort level" ;). I start off recommending acrylic thicknesses to my customers that I think will bow less than 1/4"...ESPECIALLY if they are keeping a saltwater tank. If they want to get job done somewhat cheaper I then offer to downgrade the material to something that shouldn't bow more than 3/8" and beef up the bracing widths, but anything greater than that and I'm simply not comfortable with it.

With the personal experience you mentioned at 1" of bowing how did that tank fare in the long run? I would imagine that level of bow would be pretty scary looking and be VERY easy to scratch while cleaning.
 
adambowersva said:
With the personal experience you mentioned at 1" of bowing how did that tank fare in the long run? I would imagine that level of bow would be pretty scary looking and be VERY easy to scratch while cleaning.
Click to expand...
I originally built the tank per spec for an LFS here in town and bowed like crazy and started to crack out in one of the corners so we added a coupla crossbraces to it and it lasted several years until the shop shut down a few years ago. All in all, the tank lasted probably 10 years or so. The tank was 72 x 24 x 12", 3/4" vertical walls and 1/2" bottom.

As for deflection tolerances, you're wise to keep them down. The more a tank bows, the easier it is to scratch, and since scratches are the biggest complaint with acrylic - best to keep the deflection to a minimum. I shoot for 1/8" total deflection but can live with 3/16". And when you build tanks to a tight deflection tolerance, strength is inherent so we don't have to worry about that *as* much :)

James
 
If you guys want to see a scary tank, the next time I stop in at one of my customer's tanks I'll try to take a perpective pic of their tank. 225g SeaClear (I think) 72x24x30 with rounded front corners made out of....drum roll...1/2" walls.

So when you measure the bow, do you take a level and place it in the middle at the apex of the bow, then measure how far that stands off either end?
 
Acrylics said:
if they have a 5x8' of Plex G, might be a cheaper way to go? unless you want to use 1" for the sump :)

Looking forward to pics :)

James
Click to expand...

i figure with the drops i can roughly make a 30 wide 48" long 18" tall sump . im thinking of taking a plastic 55 gallon drum and cutting in in half to put live rock in so its not in the sump ... but i figure might as well use up the left overs as i wont have a need for them ... ill get a small 4x8 sheet of 3/8 for the dividers


i do have one other question , and that is a coast to coast over flow , im a horrible drawer , so ill try to discribe what im wanting to do . i would like to have the overflow outside of the tank , and im thinking , would it be possible , after the tank is assembled , to router a slot in one end of the tank {48" side} route it so its 44" long this way there is 2" of material on each side , and then route it only 1" tall .... maybe router it 1-2" down from the top ..... and then make a box for the outside 6" tall 46" long 6" deep {give or take} i could use some of the left over 1" material so its beefy .... ill try to draw something up if its not described good enough .

thanks again james and floyd !
 
camaroboy8691 said:
i do have one other question , and that is a coast to coast over flow , im a horrible drawer , so ill try to discribe what im wanting to do . i would like to have the overflow outside of the tank , and im thinking , would it be possible , after the tank is assembled , to router a slot in one end of the tank {48" side} route it so its 44" long this way there is 2" of material on each side , and then route it only 1" tall .... maybe router it 1-2" down from the top ..... and then make a box for the outside 6" tall 46" long 6" deep {give or take} i could use some of the left over 1" material so its beefy .... ill try to draw something up if its not described good enough .
Click to expand...
Makes perfect sense, but I would recommend making the slot prior to gluing anything together as it's much easier. And go in a little more than 1" on the end panel - you'll want a good gluing surface on which to glue the overflow and a flush cut edge isn't always the best.

That said, it is possible to do it after assembly, just don't like taking a router to a fully assembled tank. One slip and we've got a bigger problem. If we screw up before it's assembled - the most we lose is that piece.

I'll try to dig up a pic or 3 later on to show you what I mean

James
 
Thanks for the input guys.

I called around today and got some quotes on material. for Plexiglas G it was alot more than I thought. I think everyone was out to rip me off.

So for
4x8 1/2" ---$577
4x8 3/4 ---$950
4x8 1" ---$1225

Thats a little more than I was barganing for. What happened to the $300-400 3/4" 4x8 sheets?

So now I am possibly going to look into doing glass or something else if I cant find some where to get the right acrylic cheaper.

Does anyone order it online and have it shipped to them without shipping killing the price? If so where do you purchase from for a good price?
 
That is way more than I pay. My latest (old) price on Plex-G 1/2" 4x8 is < $350 so yeah, shop around. Laird, Port, Sabic.
 
Last edited:
james , thanks , ill do it before assembly . any pics would be great .


A couple clowns , where are you located ? i got fresh price qoutes today from piedmont plastics . there based out of maryland {i think}, but have warehouses every where .... heres what i got for price qoutes

pm2 this is the non printed stuff i just got schooled on ....

3/4 4/8 sheet is 351.13 a sheet

1" 4/8 sheet is 483.45

the plex g

3/4 is 395.00 sheet

1" 600.95 sheet

these are not delivered prices they ship truck frieght but shouldnt be to bad,

these numbers are from today ,,,hopefully that can help you alittle .
 
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