Acrylic fabrication questions? I can help!

[SuperNemo]

Floyd, I'm aware that there needs to be a space. My understanding of bonding side by side is that you leave a 1/16 or 1/8 gap in between the two pieces and fill with 42. My question was why did Phixer choose to bond the acrylic via a 5 degree cut versus a 45 degree or even a 90 degree. Or is Phixer's two piece being bonded have different angles, i.e. one sheet in 90 degree and the other has a 5 degree cut and 42 is filled in between to bond the two sheets.

I believe that James did mention that a 45 degree bonding would leave a less visable line in between the sheets.

Another question, I have is, what if the sheets that you purchase are not exactly the same thickness (I dont mean bonding 1/2 with 3/8, I mean ordering 2 sheets of 1/2 and they are slightly off. Even a very small variance in sheet thickness would throw off the bonding of the two sheets side by side. Or is the higher quality acrylic such as Polycast better in terms of quality and more uniform in thickness.

 

[Acrylics]

Floyd, I'm aware that there needs to be a space. My understanding of bonding side by side is that you leave a 1/16 or 1/8 gap in between the two pieces and fill with 42. My question was why did Phixer choose to bond the acrylic via a 5 degree cut versus a 45 degree or even a 90 degree. Or is Phixer's two piece being bonded have different angles, i.e. one sheet in 90 degree and the other has a 5 degree cut and 42 is filled in between to bond the two sheets.

I believe that James did mention that a 45 degree bonding would leave a less visable line in between the sheets.

Personally, I use a 45 degree angle for a few reasons - but ease of finish work and clarity are the 2 main reasons.

If engineered well and the joints are done perfectly - any angle should work - but it's a lot better and easier with the bigger angle cuts on there IME/IMO

The biggest problem is getting the bottom of 2 sheets to sit perfectly flat on the table to keep 40/42 from running underneath.

..Align the pieces, dam the ends, apply tape such as blue painting tape on both pieces such that the tape runs parallel to the joint but about 1" away from the joint, apply the resin overfilling biy a good bit but not enough to run all over.. then after a few minutes add a little more resin to the top and push the 2 pieces a little closer together. This should push a little of the resin out of the joint, this is necessary. Repeat if needed in a few more minutes.

The idea is to only have major finish work on one side.

Another question, I have is, what if the sheets that you purchase are not exactly the same thickness (I dont mean bonding 1/2 with 3/8, I mean ordering 2 sheets of 1/2 and they are slightly off. Even a very small variance in sheet thickness would throw off the bonding of the two sheets side by side. Or is the higher quality acrylic such as Polycast better in terms of quality and more uniform in thickness.

no, all cast materials vary in thickness. The trick is to sort through enough sheets to get both ends to be approximately the same thickness. I'll sort through a good bit to get sheets that are within .010-.020"

HTH,
James

 

[kevantheman35]

can someone tell me if white acrylic and sanilite are the same thing? I am thinking of making a sump with 3 sides sanilite, and the front clear acrylic. Also what epoxy would work best?

 

[SuperNemo]

..Align the pieces, dam the ends, apply tape such as blue painting tape on both pieces such that the tape runs parallel to the joint but about 1" away from the joint, apply the resin overfilling biy a good bit but not enough to run all over.. then after a few minutes add a little more resin to the top and push the 2 pieces a little closer together. This should push a little of the resin out of the joint, this is necessary. Repeat if needed in a few more minutes.

James, the surface that we use for the bonding, which would you say is better. 1) plain flat surface, 2) flat surface with a grove cut in for excess to flow out underneath 3) void space in between the two sheets (two separate flat surface, which is what i have seen members do)

If you were to lay the two pieces together on a plain flat surface, how do you ensure that there is no "spot" that is not filled in properly. Would pushing the two pieces together after a few minutes eliminate that.

I would think that having a grove cut on the surface where the gap between the two sheets are would allow excess to flow out past the two pieces (bottom part).

From what I have seen of the two members that did the longer sheet bonding, they went with option 3, which is to have a void space under the sheets and place blue tape underneath to prevent excess from flowing out. Would you recommend this method as being the easiest. I would think that they would have to worry about the surface they are using to be flat, the piece of plywood the acrylic is sitting on to be flat and even (two separate pieces) and the acrylic sitting flat on top of that.

Also, since we dont have the option of sifting through lots of sheets of acrylic, what would you recommend if the sheets that we order have a small variance in thickness.

Thanks for your input.

 

[Floyd R Turbo]

can someone tell me if white acrylic and sanilite are the same thing? I am thinking of making a sump with 3 sides sanilite, and the front clear acrylic. Also what epoxy would work best?

Not even close. I had never heard of Sanilite until now, but a quick google search reveals that it is cutting board material, HDPE (high density polyethylene), do not use this for aquariums at all IMO, not sure how you would even bond it or if it would be pressure safe

 

[coffeetwitch]

With as many times as this thread has been split and the ongoing questions and specific replies, can we get a refresher post with some rules of thumb about thickness, when to brace and or rim, and order of preference of which brand/type of cast acrylic to use?

 

[dattack]

I was wondering if James have time to which at what thickness of acrylic would you prefer weld on 40/42 over solvent cement.

 

[Floyd R Turbo]

With as many times as this thread has been split and the ongoing questions and specific replies, can we get a refresher post with some rules of thumb about thickness, when to brace and or rim, and order of preference of which brand/type of cast acrylic to use?

From James [my comment in brackets]

eurobracing.. start with 3" eurobrace on any tank.. [perimeter]

24" high, use 1/2" minimum [walls]
30" high, use 3/4" minimum
36" high, use 1" minimum

with these in mind, I recommend a 6" wide crossbrace every 24" of tank length. So a 48 x 24" will have 3" eurobrace and a 6" crossbrace. If the same tank were 72" long - just one more crossbrace. At 8' length, I recommend jumping up one material thickness [walls mainly, but increasing euro won't hurt] to keep deflection down.

There are times when someone's lighting scheme doesn't match the above formula. Ie., if someone wants an 8' tank but only 3 cutouts in the top. In such cases, I recommend increasing the eurobrace width to 4.5" and increasing the width of the crossbraces to 8".

I was wondering if James have time to which at what thickness of acrylic would you prefer weld on 40/42 over solvent cement.

I don't think it's so much a matter of thickness as it is application. I recall seeing that James uses solvent up to 2 or even 2.5" thick (need a #16 high flow needle and helpers, but solvent still is good).

working with beyond 2.5" thick material I believe he considers a trade secret.

 

[coffeetwitch]

thanks floyd. what's the general consensus on material?

 

[Floyd R Turbo]

Oh yeah

#1) Polycast
#2) Plexiglas-G

#3 used to be Acrylite GP, but now anything <1" is made in China, 1" and over in Germany. Supposedly the German stuff is good. I spoke with a Cyro guy (long time employee) and he said that the word on the street is that the China Cyro product bonds up similar to Reynolds. I don't have a frame of reference here, but from what I understand Reynolds is "harder" or something like that, so you need a bit longer of a soak time in order to get enough "bite" into the material.

In the same discussion, the Cyro guy told me that "he doesn't know any reputable aquarium builder" that used solvent to bond acrylic because it was a weaker joint. When I asked him how long he let the solvent joint cure he was stumped, like he hadn't considered that. I didn't bother to ask him is he used the pins method. James has posted info on the thread w/r to destructive testing of properly cured joints and the material breaks before the joint when done right.

....but not all do it right. Even the "oldest manufacturer in the nation" builds tanks that look ridiculous because they didn't follow good practices.

 

[kevantheman35]

Thanks for the info floyd, do you happen to have a link to some decent priced acrylic suitable?

 

[Floyd R Turbo]

google

Sabic Polymershapes
Laird Plastics
Port Plastics
Regal Plastics

or search locally via google, yellow pages, etc. Glass shops might know where to source acrylic locally.

 

[Floyd R Turbo]

Also if you're just talking sumps, frag tanks, etc - nothing "show" quality, then also you can consider the "generic" Plexiglas-G. This is referred to as PMACS, it is made by Arkema (parent company of Plexiglas) and is cell cast acrylic with a plain paper mask (-G is printed on one side, this stuff is not). It does not have a guarantee/warranty but in reality neither does -G because once you machine the stuff, the warranty is void (unless you buy $200K/yr, then they kiss your behind).

PMACS supposedly can have "inflections" or "specs" in it, but IMO it's exactly the same as -G. I've built plenty of tanks with it, you can get it in black also. 3/8" and 1/2" prices are usually pretty good

 

[dattack]

Also if you're just talking sumps, frag tanks, etc - nothing "show" quality, then also you can consider the "generic" Plexiglas-G. This is referred to as PMACS, it is made by Arkema (parent company of Plexiglas) and is cell cast acrylic with a plain paper mask (-G is printed on one side, this stuff is not). It does not have a guarantee/warranty but in reality neither does -G because once you machine the stuff, the warranty is void (unless you buy $200K/yr, then they kiss your behind).

PMACS supposedly can have "inflections" or "specs" in it, but IMO it's exactly the same as -G. I've built plenty of tanks with it, you can get it in black also. 3/8" and 1/2" prices are usually pretty good

I think this stuff is actually pretty good. It glues better than acrylite. I did use polycast once but too expensive.

 

[Floyd R Turbo]

That's because Acrylite <1" is made in China and is a little different. I wouldn't know though, never used acrylite

 

[Cobia302]

Hello I hope I am in the right section. I have a aquaponics system. I have been growing tomatoes, lettuce, raspberries and others. I have my whole system set up and running good. The fish are in plastic tubs right now. I have been given scraps of polycarbonate plastic for free and decided to make a fish tank with it. It is 1/2 inch thick but in some places I drilled out holes and put in 1/8th diameter screws to hold it togeather because I couldn't find a good material to bond it together so in some spots the material is 3/8th inch thick where the screws are. I found this site today and found out a lot of good info about what I am suppose to use to bond the materials together and that I should have not have used screws and what all I did wrong. I was wondering after i take it all apart could I use the weld-on 16 on it and screwed it back together if that would work. Or should I cut 1 inch off from each side and use the weld-on 4 to fasten it all together. I don't have a table saw so I am using a skill saw to cut my pieces so my angles are not exactly the same so that makes me worry about to big of gaps in some places. Will the #4 fill the gaps or is that what the #16 is for.

 

[Floyd R Turbo]

I don't know Polycarbonate (PC for short) so someone else can chime in here. But what I can tell you is that you are going to have to cut away all the parts that you screwed into so that the potentially weak areas are gone.

PC is harder to work with because it is "grabby", so you have to be really careful, it was recommended to me that templates be used when routing PC instead of just sliding across a router table. So that's #1.

the 45 degree corner is what I would consider a more complicated technique and if this is your first build, I wouldn't try it, especially if you are rough cutting

#4 is not a gap filler. #16 is a very poor product. WO40 is a gap filler.

If this tank is only going to be partially full, like 1/2 way or less, might be OK without a eurobrace on the top.

Your threaded fitting in the holes on the back look siliconed in? bulkheads should be used, silicone won't hold.

Without a table saw, you're going to end up with very poor rough cut edges, getting things square and parallel is going to be a pain, and that is important. You can use a level and clamp it on to the piece on a large table to make a reference fence to run your saw across, but you will spend a lot of prep time making sure that level is parallel to the other edge you are going to cut, then do the same to square the adjacent edge, etc.

 

[Cobia302]

I don't know Polycarbonate (PC for short) so someone else can chime in here. But what I can tell you is that you are going to have to cut away all the parts that you screwed into so that the potentially weak areas are gone.

PC is harder to work with because it is "grabby", so you have to be really careful, it was recommended to me that templates be used when routing PC instead of just sliding across a router table. So that's #1.

the 45 degree corner is what I would consider a more complicated technique and if this is your first build, I wouldn't try it, especially if you are rough cutting

#4 is not a gap filler. #16 is a very poor product. WO40 is a gap filler.

If this tank is only going to be partially full, like 1/2 way or less, might be OK without a eurobrace on the top.

Your threaded fitting in the holes on the back look siliconed in? bulkheads should be used, silicone won't hold.

Without a table saw, you're going to end up with very poor rough cut edges, getting things square and parallel is going to be a pain, and that is important. You can use a level and clamp it on to the piece on a large table to make a reference fence to run your saw across, but you will spend a lot of prep time making sure that level is parallel to the other edge you are going to cut, then do the same to square the adjacent edge, etc.

ok thank u i have a lot of changes to make.

 

[Cobia302]

One last thing is, has anyone heard of or experienced a fish tank made of Polycarbonate screwed together explode or fall apart? Or any other situations with a fish tank being screwed together not working?

 

[Phixer]

Phixer,

Why did you decide to join the sheet with a 5 degree cut? The two members that I know of that made a 12ft tank, one did a straight 90 degree bond and one did a 45 degree bond.

Is there any reason for choosing the straight 90 degree or in your case 5 degrees

Supernemo

The reason I decided to use 5 degree bevels on each 4 ft section was reached after about 3 years of research. I visited the Dubai aquarium, Seaworld, Scripps and the local aquarium here in downtown Denver in addition to a bunch of others overseas while on active duty. Then I talked to Cyro, IPS, Reynolds here in CO and about a dozen fabrication shops and read everything I could find. Some recommended kerf joints, some lap joints and one shop even recommended a type of ball and socket joint??? All were problematic when considering the propensity for bubbles when casting the joint and future crazing propagating from the thinner parts of the material due to prolonged hydrostatic pressure. Probably why none of the tanks I visited used these joints.

Although two 22.5 degree bevels equaling one 45 degree void would provide a lot of surface area for the cement to bite into it would also increase the likelyhood of bubbles forming when casting the joint, (a minor issue which could be resolved during casting by removing them with a hypedermic needle and syrenge), however a 45 degree butt joint for a 48" tall tank would also require much more cement and would place more demand on the shear strength of the cement rather than the base material because of the distance between the two panels at the largest gap located at the top of the V since it would be much greater. Know what I mean?

I decided against a 90 degree butt joint because I didnt feel this was enough surface area for the cement, although many tanks I visited (sorry not able to upload photos on this site for some reason) appeared to be built this way. I also reviewed a couple acrylic fabrication manuals to see what they recommended. The general consensus was to use a V joint and with 5 degree bevels on each end for 2.250 thick material. The panels will be butted together with about an 1/8" gap between the two at the bottom.

For me.. two (5) degree bevels making a 10 degree void at the top was the most logical way to join these two panels of this thickness. Sorry for the long winded reply. There is more science to this behind my decision but this is long enough.

During my research and observations... one commonality I found was that all of these aquariums meaning every public acrylic aquarium I inspected throughout the world is made using 2 part polymerizable cement. PS30 or WO 40/42. The concrete and fiberglass tanks used acrylic windows sealed in place with Dow 795. Solvent bonding has it's place. I've just never seen it used on the big public aquariums.