Acrylic Fabrication Q & A

[West1]

There should be no sanding involved at all. if you have bubbles then you did not prep the edges properly, blow out any dust, and/or utilize the pins method properly.

Pcs were cut from a CNC. I did not use the pins method at the start, that was the reason for the bubbles. Second round I did

 

[Turbo's Aquatics]

I glued some acrylic together and I see some bubbles in the seam, do I need to take it off and sand it down again? Or is there a different way to get a full seal?

When you say "take it off" what do you mean?

 

[West1]

When you say "take it off" what do you mean?

I was wondering if I needed to remove the 2 pieces of acrylic and bond them together again, which I did. The sides of the overflow had a small section that was extremely rough so I used some sandpaper to get the acrylic fairly flat again.
Flipped the front panel and did the pins method. Let it dry for about 1-2 minutes and turned the finished piece upside down and placed a gallon of water on top for pressure.

I was just reading "the fix" on page 6, post [HASHTAG]#103[/HASHTAG].
The fix, for peace of mind, is similar to the sump baffle fix, with one slight difference. Simply take a piece of 1/4" material that is about 3/4" or so wide and about the same length as the bottom panel (it doesn't have to run the full length, it can fall short of the corners by an inch or more) and solvent weld it to the bottom panel of the overflow box, perpendicular to it, flush with the back edge (the edge that will "touch" the glass). Now you have extended the surface area for the bottom/back edge of the overflow box. When you silicone the box in, instead of a 1/4" wide area of acrylic-to-glass, you now have a 1" wide area. This significantly reduces the chances that your overflow box will break away. The solvent weld doesn't have to be perfect in this case either, a rough-cut edge that is nice and straight, followed up by a few scrapes with a razor blade, and capillary welded in place (using the "preferred" capillary method) will work just fine.

Is it overkill if I bond a piece of 1/4 acrylic to every inside part that touches the class (3 for the bottom and 2 for the back)?
When you say "...bottom panel of the overflow box, perpendicular to it, flush with the back edge (the edge that will "touch" the glass)," does this piece fit flush from the front inside of the overflow to the glass (bonded to the inside bottom sides of a 3 pc square overflow)?

 

[TaylorPilot]

Ideally you shouldn't sand the edges you are about to glue. Sanding rounds them over. Ideally use a router table to prep the edges, at the least a scraper paying close attention to hold perpendicular to the part. Also, only allowing to dry for 2-3 minutes before moving. I leave small stuff clamped for at least 8 hours. If I have to actually flip the part to the do another side, overnight to 24 hours. Those parts have barely began to cure at 3 minutes. That may be part of your issue. Stressing them and allowing air to get in.

 

[Turbo's Aquatics]

My mind is running on sudafed, mucinex, and caffeine today...I need a picture

 

[West1]

My mind is running on sudafed, mucinex, and caffeine today...I need a picture

I will post a picture when I get home

Ideally you shouldn't sand the edges you are about to glue. Sanding rounds them over. Ideally use a router table to prep the edges, at the least a scraper paying close attention to hold perpendicular to the part. Also, only allowing to dry for 2-3 minutes before moving. I leave small stuff clamped for at least 8 hours. If I have to actually flip the part to the do another side, overnight to 24 hours. Those parts have barely began to cure at 3 minutes. That may be part of your issue. Stressing them and allowing air to get in.

Got it, I thought sandpaper wouldn't hurt. The good is, I did just enough to see the seam has no air bubbles.

 

[TherealplexiG]

It's pretty tricky to use the pins method. The first side I thought i pulled the pins to fast. 2nd side, i left them for approx 40 seconds and it still seemed to long. Acrylic would slide when I attempted to pull a pin. After a couple tries Im happy with the results,

In the words of lowell lemon: that's art of acrylic fabrication.

 

[TherealplexiG]

 

[West1]

My mind is running on sudafed, mucinex, and caffeine today...I need a picture

Here it is

Is it overkill to solvent weld these small pieces as is?
I will be using Momentive IS800 series silicone to place the acrylic overflow in a biocube (glass).

 

[cromag27]

That's why I said no sanding. the momentive you want to use is 100 series.

 

[cromag27]

My mind is running on sudafed, mucinex, and caffeine today...I need a picture

 

[TherealplexiG]

@TaylorPilot
What thickness do ya use on your overflows?

 

[TherealplexiG]

Here it is

Should have gone black, clear would be something like PVC at naturist beach.

 

[West1]

Should have gone black, clear would be something like PVC at naturist beach.

Its going to get covered


The way I placed the pieces of acrylic at the bottom of the overflow, is this the way they should be solvent weld? They can be moved, not cemented in.

 

[Turbo's Aquatics]

Here it is
Is it overkill to solvent weld these small pieces as is?
I will be using Momentive IS800 series silicone to place the acrylic overflow in a biocube (glass).

Its going to get covered
The way I placed the pieces of acrylic at the bottom of the overflow, is this the way they should be solvent weld? They can be moved, not cemented in.

just try to get them so that they line up with the edges that are going to be in contact with the glass.
Silicone per @cromag08's recommendation
What are you going to cover it with?

ugh

 

[West1]

just try to get them so that they line up with the edges that are going to be in contact with the glass.
Silicone per @cromag08's recommendation
What are you going to cover it with?


ugh

DIY live rock on the bottom, back and where the plastic of the biocube covers the sides.

 

[TherealplexiG]

@Floyd R Turbo
I know you done alot of research on weir flow. Could you tell me whether this should work or not. Tank dimension all in one nano braced, 18" L x 16" D x 12" H. Attaching a render for ref. flow approx 300 gallons per hour. Dimensions on the attached are in mm. My target is half of the weir height when the pump is running.

 

[Turbo's Aquatics]

Oh man you're going to make me dig out my weir estimator.....

Ok...

Width of notch = 6mm = 0.236"
number of notches = 11
Length of weir = 2.596"
Water @ half height = 12.5mm = 0.429"
Discharge coefficient for notched weir = 0.55

Q (flow) = 146 GPH

The water depth needs to get up to 0.81" (20.5mm) before you hit 300 GPH.

 

[TherealplexiG]

The water depth needs to get up to 0.81" (20.5mm) before you hit 300 GPH.

If i understand correctly the water would rise upto 20.5 mm, so either i increase the weir height or increase the weirs. Could you explain how that formula works?

Q (flow) = 146 GPH

146?

 

[Turbo's Aquatics]

146 GPH at 12.5mm (halfway up the notches) and that is without any buildup on the notches. Over time, you will end up with a decrease in flow due to gunk building up on the sides of the notches, so water will rise up more to achieve the same flow rate

The formula is a simple weir calculation

Q = (Cd) * (2/3) * (B) * sqrt(2g) * (H^(3/2)) <---- last term is H to the power of 3/2 or 1.5

Cd = coefficient of discharge
B = Width of notch
g = gravity
H = Height of weir (or water height above the top of the weir, or in this instance, the lowest point of the notches, etc)

Cd is 1.0 for a coast-to-coast and 0.55 for a 1/4" notch, everything else pulls out and the formula becomes

Q = 288 * Cd * B * (H^(3/2))

^this is all in inches

So you just plug in your total width of all notches (0.236 * 11 = B) and your water height above them (H) and Cd= 0.55 and plug & chug