Acrylic fabrication questions? I can help!

[smartwater101]

I've glued the tank and the majority of it looks great. But there are 2 edges that are a complete mess. I was considering using smaller pieces to reinforce those edges.... do you have any suggestions? thanks

 

[kmu]

I would use 1.250" minimum thickness for that height. 1" is too thin for a tank 3ft tall...IMO. Using the same dimensions of 72" long and 42" wide and those cutout dimensions I would use two cutouts (lower illustration). Better structural rigidity and less stress. You would still have enough area for good gas exchange considering a 3ft depth. The top panel behaves differently than the others, it is subjected to compression stress as well being pulled apart. 3 cutouts for a tank 6ft long is greater propensity for cracks and buckling due to less material, not much gained for surface area either vs 2 cutouts with good water movement. I would also radius the inside edges (see photos attached). Im refinishing this tank now (scratch removal). It's 28" tall (inside) using 7/8" thick material ...(strange?) , 30" wide and 120" long. Id like to show you the deflection but it's empty. System is acting up when attempting to open them, hopefully you can open them full size or export them and open with MS Paint.

Phixer, THX for the reply, gonna quote it in 1.25" also, yes the top opening will have radius corners.

The overall height of the tank will be 36" tall, with 1" thick acrylic the inside of the tank will be 34" tall and the water level will be 33" tall.

 

[Floyd R Turbo]

I would use 1.250" minimum thickness for that height. 1" is too thin for a tank 3ft tall...IMO. Using the same dimensions of 72" long and 42" wide and those cutout dimensions I would use two cutouts (lower illustration). Better structural rigidity and less stress. You would still have enough area for good gas exchange considering a 3ft depth. The top panel behaves differently than the others, it is subjected to compression stress as well being pulled apart. 3 cutouts for a tank 6ft long is greater propensity for cracks and buckling due to less material, not much gained for surface area either vs 2 cutouts with good water movement. I would also radius the inside edges (see photos attached). Im refinishing this tank now (scratch removal). It's 28" tall (inside) using 7/8" thick material ...(strange?) , 30" wide and 120" long. Id like to show you the deflection but it's empty. System is acting up when attempting to open them, hopefully you can open them full size or export them and open with MS Paint.

Just to give another perspective, here is Jame's (Acrylics) formula

start with 3" eurobrace on any tank..

24" high, use 1/2" minimum
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 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".

Iv'e been using this formula, 1.5" radius corners, and material thickness minimums above, for many years and I have *never* had a tank fail.

If someone doesn't want the crossbrace - they simply have to make the material thicker, and/or increase the width of eurobrace to maintain rigidity.

For your 42 x 72 tank, I guess I can't see how going with the 2-opening scheme would be better. Phixer perhaps you can explain that reasoning. I would think that taking the 3-opening version and then thinning the perimeter but adding a crossbrace along the center axis the long way (making 6 openings) might actually be the best way. So you would have a 3" perimeter brace, then 6" wide cross braces at 24" and 48" and then one across the center of the long dimension, also 6". You would lose some access hole space, and your rear strip would have to be 6" wide still to accommodate the holes in the top.

But the other thing you can do in order to thin out the bracing a bit is increase the thickness of the brace, at cost of course.

Just some food for thought, and not based on experience, just repeating what I have picked up along the way...

 

[Phixer]

Here's why IMO. Considering 1" thick material at 36" high must design with structural rigidity in mind. Deflection (bowing) is greatest at the center of the front (viewing) and back panels. As the force of the water pushes outwards using 3 cutouts we are looking at an area 6" wide of 1" thick acrylic resisting this force at it's greatest point ,the center. This section will see stress trying to pull it in a perpendicular direction as well as the torsional stress trying to twist it. I believe this stress it will localize in the 4 corners of the center cutout (1" thick material = less resistance to cracking) also why radiused inside corners are so important. With 2 cutouts your looking at an 8" wide perimeter with a 42 inch long crossmember of 1" thick acrylic being pulled lengthwise rather than perpendicular. Although there are no grain boundaries such as in wood we are still looking at only 6" of 1" material in an area where deflection will be greatest vs 42" pulled in both directions.

If using 1.250 I believe the 3 cutout design would work ok but I like that center brace in consideration of the direction of force and liken it to rebar in concrete.

 

[Floyd R Turbo]

I can understand your logic regarding the point of highest deflection, but I would defer back to James' formula which he has been using for decades without fail, and he doesn't make a mention of this. Remember that the euro is connected fully across the top edge of the front panel, and this connection distributes the pressures. Increasing the width of the perimeter euro would distribute this stress more evenly. Increasing the width of the crossbraces would allow this stress to "channel" across a greater area. Adding the radiused corners to the cutouts allows this stress to transfer to the crossbraces more evenly instead of concentrating it at the corner.

The problem with crackouts is a result of not putting a radius on the cutouts. Also, from my discussions with a few guys at Cyro, they also mentioned that any sharp angles will cause the stress to focus in that location. Meaning that not only is it important to radius the corners, but it is also important to round off sharp edges - namely, the euro cutouts. I was already doing this (putting a 1/8" round on both the inside and outside of the euro cutouts) but this was mainly done so that one does not cut their hands/arms on the edges of the opening. Even knocking them down with a razor blade by scraping it across the sharp edge at a 45 degree angle 5 or 6 times is enough to remove potential point stresses than can 'gather' on sharp edges.

 

[reefer.alx]

Acrylic bubbles in seam

Acrylic bubbles in seam

Heyy everyone,

Long time lurker, first time poster!
Sorry to make my first post a cry for help, but here it is :bigeyes:

I recently purchased an acrylic tank from an individual who makes them at home.
I paid after I accepted the quote, and then picked it up when it was finished last night (it was dark)

This morning I checked out the seams, there seeeeemmmmmsssss to be obvious excess bubbles. Lots of bubbles from micro to larger stretch across the seam.
There are many 1 to 2" patches of these bubbles.

The individual assures me that they have had experience with those joints and would not give out anything that they'd think would fail...

I was told that the company that cut the acrylic used a router and that he used weld on 4 with a bead of 16?

Attached are some quick cellphone pics
I'm not crazy if I pursue this guy to get the tanks refunded/redone? Right?? :sad2:

 

[Floyd R Turbo]

IMO, these are completely unacceptable. It may hold water through whatever warranty period he is offering, but beyond that, good luck.

If I made a tank that had joints like that, I would rebuild it. It would have never left my shop.

Just to put this into perspective though, I recently viewed a tank that was made by "the oldest tank manufacturer in the US" that had some joints with similar looking non-quality, they claimed to do the exact same thing - run WO16 along any joints with "bubbles" on them. When I sent him pictures of the joint in question, he said "that did not leave the shop in that condition" and that it "must have opened up on the truck".

This is total BS, because that joint would have had to set long enough to flush trim off the lip before it could be boxed up and put on the truck, meaning that it was just poor construction technique or not letting the joint cure long enough before handling, probably among many other things.

He also informed me that since they are in the southwest, and it's 100F + outside, that the solvent starts to dry up before the joint can be set, etc - all excuses. Any shop with a damn would keep their shop temps at a reasonable temperature and humidity for solvent welding, and would allow a joint to cure properly before handling.

The other factor is acrylic sheet quality. It is highly improbable to get a sheet that is exactly the same thickness throughout the entire sheet. So when you are setting up a joint, the edge that is being bonded might be 100% straight and flat, routed perfectly, but that doesn't matter when the sheet you are bonding it to is not the same thickness throughout. That is why you use MDF with camper shell foam on both sides, and shims and pins. The foam and shims allow you to tighten up the joint so that air can't creep in to the areas where the flat sheet has a thickness inconsistency.

Anyways you cut it, whoever built this tank for you has no business building tanks, unless he's making them really cheap, and then you just get what you pay for.

Sorry for the bad news but that's just my 2c.

 

[kmu]

Just to give another perspective, here is Jame's (Acrylics) formula



For your 42 x 72 tank, I guess I can't see how going with the 2-opening scheme would be better. Phixer perhaps you can explain that reasoning. I would think that taking the 3-opening version and then thinning the perimeter but adding a crossbrace along the center axis the long way (making 6 openings) might actually be the best way. So you would have a 3" perimeter brace, then 6" wide cross braces at 24" and 48" and then one across the center of the long dimension, also 6". You would lose some access hole space, and your rear strip would have to be 6" wide still to accommodate the holes in the top.

But the other thing you can do in order to thin out the bracing a bit is increase the thickness of the brace, at cost of course.

Just some food for thought, and not based on experience, just repeating what I have picked up along the way...

Here's why IMO. Considering 1" thick material at 36" high must design with structural rigidity in mind. Deflection (bowing) is greatest at the center of the front (viewing) and back panels. As the force of the water pushes outwards using 3 cutouts we are looking at an area 6" wide of 1" thick acrylic resisting this force at it's greatest point ,the center. This section will see stress trying to pull it in a perpendicular direction as well as the torsional stress trying to twist it. I believe this stress it will localize in the 4 corners of the center cutout (1" thick material = less resistance to cracking) also why radiused inside corners are so important. With 2 cutouts your looking at an 8" wide perimeter with a 42 inch long crossmember of 1" thick acrylic being pulled lengthwise rather than perpendicular. Although there are no grain boundaries such as in wood we are still looking at only 6" of 1" material in an area where deflection will be greatest vs 42" pulled in both directions.

If using 1.250 I believe the 3 cutout design would work ok but I like that center brace in consideration of the direction of force and liken it to rebar in concrete.

I can understand your logic regarding the point of highest deflection, but I would defer back to James' formula which he has been using for decades without fail, and he doesn't make a mention of this. Remember that the euro is connected fully across the top edge of the front panel, and this connection distributes the pressures. Increasing the width of the perimeter euro would distribute this stress more evenly. Increasing the width of the crossbraces would allow this stress to "channel" across a greater area. Adding the radiused corners to the cutouts allows this stress to transfer to the crossbraces more evenly instead of concentrating it at the corner.

The problem with crackouts is a result of not putting a radius on the cutouts. Also, from my discussions with a few guys at Cyro, they also mentioned that any sharp angles will cause the stress to focus in that location. Meaning that not only is it important to radius the corners, but it is also important to round off sharp edges - namely, the euro cutouts. I was already doing this (putting a 1/8" round on both the inside and outside of the euro cutouts) but this was mainly done so that one does not cut their hands/arms on the edges of the opening. Even knocking them down with a razor blade by scraping it across the sharp edge at a 45 degree angle 5 or 6 times is enough to remove potential point stresses than can 'gather' on sharp edges.

The price of the acrylic sheets of 1-1/4" Vs 1" is around 55% more, so we need to make it work.

Which TOP design gives the best strength? will make radiused corners on the top brace.

would the overflow being external reduce its strength because of the overflow teeths are on the main back panel?

I really appreciate all the help and suggestions

THX in advance

 

[Floyd R Turbo]

I've glued the tank and the majority of it looks great. But there are 2 edges that are a complete mess. I was considering using smaller pieces to reinforce those edges.... do you have any suggestions? thanks

Can you post a few more pics from different angles? can't quite see this joint very well in this pic due to reflections, etc. Need close-ups

 

[Floyd R Turbo]

The price of the acrylic sheets of 1-1/4" Vs 1" is around 55% more, so we need to make it work.

Which TOP design gives the best strength? will make radiused corners on the top brace.

would the overflow being external reduce its strength because of the overflow teeths are on the main back panel?

I really appreciate all the help and suggestions

THX in advance

IMO, the 3 cutout design is best.

The overflow box bonded on the back should shore up the back panel. If you make the teeth such that they don't extend all the way to the top of the back piece, this will allow for a full bond across the top of the back edge to the euro, but the presence of the teeth will weaken that area, so make sure the overflow box is the same thickness material (use the scrap from the euro cutouts if you can). Also I would make sure you allow a proper cure time for the overflow box joints as these will be resisting outward bowing pressure. Another reason to have a thick back panel.

 

[Phixer]

I've glued the tank and the majority of it looks great. But there are 2 edges that are a complete mess. I was considering using smaller pieces to reinforce those edges.... do you have any suggestions? thanks

Like this.

 

[Phixer]

The price of the acrylic sheets of 1-1/4" Vs 1" is around 55% more, so we need to make it work.

Which TOP design gives the best strength? will make radiused corners on the top brace.

would the overflow being external reduce its strength because of the overflow teeths are on the main back panel?

I really appreciate all the help and suggestions

THX in advance

$$ sure is. Hope you can use Polycast GP or Reynolds R cast. IMO/IME, the design must be based on the properties of the material you are using.

For 1" thick material the 2 cut out design is my recommendation.

Yes, remember for this application (1" thick material) you will have an overflow located in the center of the panel, the area of greatest deflection (weakened more so if using a 3 cutout top and 1" thick material which will inherently deflect more at that height). Anytime you remove material you lose structural integrity.

We all have different backrounds and perspectives on how to fabricate, why this thread is so valuable. If you get a chance, study the Handbook of Acrylics for Submersibles, Hyperbaric Chambers, and Aquaria by Jerry Stachiw, most public libraries can special order it for you as it's costly to purchase. It gets deep (no pun intended) but it will explain the physics behind the design and address characteristics of the materials.

If your interested in marine engineering, oceanography or aircraft pressurization (believe it or not) much of it is applicable to what we do although the pressure is normally pushing is the other direction LOL...

 

[Phixer]

Heyy everyone,

Long time lurker, first time poster!
Sorry to make my first post a cry for help, but here it is :bigeyes:

I recently purchased an acrylic tank from an individual who makes them at home.
I paid after I accepted the quote, and then picked it up when it was finished last night (it was dark)

This morning I checked out the seams, there seeeeemmmmmsssss to be obvious excess bubbles. Lots of bubbles from micro to larger stretch across the seam.
There are many 1 to 2" patches of these bubbles.

The individual assures me that they have had experience with those joints and would not give out anything that they'd think would fail...

I was told that the company that cut the acrylic used a router and that he used weld on 4 with a bead of 16?

Attached are some quick cellphone pics
I'm not crazy if I pursue this guy to get the tanks refunded/redone? Right?? :sad2:

Sorry to hear. Concur, I would return the tank, thats not a professional job. Any warranty provided for workmanship? If you attempt to modify or repair your stuck with it.

How thick is the material?

 

[kmu]

$$ sure is. Hope you can use Polycast GP or Reynolds R cast. IMO/IME, the design must be based on the properties of the material you are using.

For 1" thick material the 2 cut out design is my recommendation.

Yes, remember for this application (1" thick material) you will have an overflow located in the center of the panel, the area of greatest deflection (weakened more so if using a 3 cutout top and 1" thick material which will inherently deflect more at that height). Anytime you remove material you lose structural integrity.

We all have different backrounds and perspectives on how to fabricate, why this thread is so valuable. If you get a chance, study the Handbook of Acrylics for Submersibles, Hyperbaric Chambers, and Aquaria by Jerry Stachiw, most public libraries can special order it for you as it's costly to purchase. It gets deep (no pun intended) but it will explain the physics behind the design and address characteristics of the materials.

If your interested in marine engineering, oceanography or aircraft pressurization (believe it or not) much of it is applicable to what we do although the pressure is normally pushing is the other direction LOL...

Phixer THX for your information

I will talk to my tank builder and get the brand of acrylic used

Just did a quick online look at some prefab acrylic tanks sold online and most use 3/4" acrylic for 36" Tall tanks, wouldn't run any of those in my house, just too thin and too much gallons to risk them getting into the floor

site #1 72"L x 36"W x 48"T uses 1" thick all around

site #2 96"L x 36"W x 36"T uses 3/4" acrylic all around

site #3 72"L x 36"W x 30"T uses 3/4" acrylic
site #3 72"L x 36"W x 36"T uses 1" acrylic (only decent thickness)


Once again THX for all your help!!!

 

[Phixer]

Of course my friend. Crazy how expensive some MFGs can be.

Acrylic is a petroleum based material maybe one reason why it costs so much. Forgot to mention before, 42" is a nice width. Have you considered an internal overflow with a Herbie design?

This link may get yanked by...The Man but I have found some great deals on here if you dont mind driving a little. Hope you find it interesting.

http://giantaquarium.wordpress.com/

 

[aaron7405]

Heyy everyone,

Long time lurker, first time poster!
Sorry to make my first post a cry for help, but here it is :bigeyes:

I recently purchased an acrylic tank from an individual who makes them at home.
I paid after I accepted the quote, and then picked it up when it was finished last night (it was dark)

This morning I checked out the seams, there seeeeemmmmmsssss to be obvious excess bubbles. Lots of bubbles from micro to larger stretch across the seam.
There are many 1 to 2" patches of these bubbles.

The individual assures me that they have had experience with those joints and would not give out anything that they'd think would fail...

I was told that the company that cut the acrylic used a router and that he used weld on 4 with a bead of 16?

Attached are some quick cellphone pics
I'm not crazy if I pursue this guy to get the tanks refunded/redone? Right?? :sad2:

Hi reeferaxl

What is the messures of our tank and what is the acrylic thicknes he is using 1/2 maybe?

IMO this bubble could be couse by looks the guy let the glue start to weld and then he move the pice to correct something leaving that kind of bubbles or he did not apply any presure to close the gaps to take out the bubbles, or the 2 pieces to bond did not complete match so thay has bigs gaps. The smaller bubbles seams like the sides was not flat and make those gaps.

Yes the compay than cuts use a router but is his responsability to plain the edges and sand them a bit to correct the router cut. some times we usea planner to do this or sand by hand both sides before glue them.

IMO than tank has to many incorrect glues.

IMO
I use weld on 3 works better than 4. On my 1/4 (sumps and small boxes )proyects we use WeldOn 3 or 4 to weld and then I apply a lay or 16 to cloese inner gaps. On the 1/2" + thick acrylic proyects we use only 40 that will close all the gaps and weld very strong. I have use 40 on proeycts 1" acrylics an the weld excelnet. bit messy and a bit expensieve than the 3 or 16but ist worth it.

 

[aaron7405]

Phixer THX for your information

I will talk to my tank builder and get the brand of acrylic used

We use Evonic Industries Cyro Acrylite GP and weld on 40 to glue it.
http://www.acrylite.net/product/acrylite/en/products/sheet/gp/pages/default.aspx

 

[kmu]

We use Evonic Industries Cyro Acrylite GP and weld on 40 to glue it.
http://www.acrylite.net/product/acrylite/en/products/sheet/gp/pages/default.aspx

THX!!!


Here are a couple of external overflow options, the single center overflow will have the overflow teeth right in the middle where most of the bowing pressure (stress) will be, the 2 overflow option would have the overflow teeth on the sides around 9" from each corner.

would the 2 overflow set up be better and stronger?

 

[Phixer]

Yes, IMO. Sure you dont want to go with an internal overflow?

 

[smartwater101]

Can you post a few more pics from different angles? can't quite see this joint very well in this pic due to reflections, etc. Need close-ups

Here is a pic of the fix. (ignore all the smudges)
The edge had two large gaps that could not be filled. I used triangle cuts and bonded them to the seams for extra support.