Acrylic fabrication questions? I can help!

[Westcoastindia]

James,
How does weather affect the solvent mix? What should be the adjustments to the concentration if say the room temp is around 30 to 35 degree Celsius.

 

[Acrylics]

Thanks Bud you the man...
I knew about the acrylic drill bits, even though I have always used regular drill bits to drill my acrylic projects.
Do you use 1/4-20 thread taps to tap 1/4" acrylic sheets? like the thumb screw on your ATS Rev3 which holds the light in?
Is 24 or 32 thread too fine for acrylic?

It's not too fine, but unless you use a lubricant, you're apt to get bad/cracked threads. 1/4-20 is the "standard" thread pattern for most of these types of things. I'm very leery of "standard" taps available at most big box stores though as they don't clear chips well at all and if using a Makita type thing - chips get clogged/melted in the flutes.

If you're doing a lot of tapping, I'd strongly suggest a spiral fluted tap such as this: http://www.osgtool.com/Product-List-Detail/EXOTAP-VA-3-Taps/303

James

 

[Acrylics]

James,
How does weather affect the solvent mix? What should be the adjustments to the concentration if say the room temp is around 30 to 35 degree Celsius.

Humid/moist air can cause what's called "blushing" in which the area around the joint turns white.

Depending on humidity, either add a touch more acid if the air is dry enough or if the air is moist - lower the MC in the solution and add something Ethylene dichloride/dichloroethane as ~35-45% of the solution. EDC will slow the reaction without adding too much acid which can cause joints to look grainy or having so much in solution that you get ooze bubbles.

HTH,
James

 

[OhMatic]

What would you use for a lubricant to tap acrylic?
Would you use lubricant when using a spiral fluted tap?

 

[Acrylics]

What would you use for a lubricant to tap acrylic?
Would you use lubricant when using a spiral fluted tap?

Brillianize works well for small tapped holes. It's a plastic cleaner and polish.
a 50:50 solution of dish soap like Dawn and water is also an excellent lubricant. And yes, lubricants get used with every tapped hole, or at least should be.

HTH,
James

 

[Westcoastindia]

James,
I don't know if I could thank you enough!
Much appreciated mate.

 

[aryth]

Generic brand

Generic brand

I am about to start building ~250 Gal tank.
It was advised many times on this thread to use quality brands (e.g., Polycast or Plexiglas-G) for a show build. Yet, it may be just too tempting to use a generic (Asian) brand because of the price and/or availability, and also because things change... So, is it still true today, do people use generic (less known) brands in big (200-300 gal) builds nowadays? What are the possible issues: structural down the road, cosmetic, gluing issues? And specifically, is it possible/ok to use a less reputable brand by overbuilding the tank?

Thanks,
Andrey

 

[Floyd R Turbo]

IMO:

1) Polycast ($$)

2) Plexiglas-G (Arkema, paper mask with green print)

3) PMACS (which is the generic cell cast version also made by Arkema, paper mask, no print)

That's all I would use for a DT, and I'm iffy on the PMACS even for that. Good for sumps, frag tanks, smaller tanks, etc. But a 250? Plex-G minimum.

Big no on asian cheap brands. Even Cyro's Acrylite GP (which is now made in China for anything under 1" thick) is off the list permanently in my book. I recently heard from Synergy Reef that they were delivered a pallet or two of Cyro GP and it was not weldable, it was that bad. That did it in for me, and that used to be top 3 so if everything else is below Acrylite GP, everything else is no good either. Again, JMO

 

[aryth]

Thanks Floyd. I understand, and I am still trying to find a better material.
Meanwhile, someone quoted me Chemcast - used to be a good brand, then some bad history. What is its status among pros nowadays?

 

[Floyd R Turbo]

Chemcast is one of those that is exactly as you say - good material, bad history. I see it used a lot, I think it's probably better than Acrylite at this point.

 

[Acrylics]

The thing with Chemcast is that it glues up beautifully, like it always has. The problems seem to come up a year or two down the road. The joints just fail, catastrophically. I don't know the reason, but a year or two under load seems to be enough. This has caused at least one tank mfg company to go out of business as they couldn't keep up with warranty returns.
Could this have changed? sure, but.. I can't trust it, at least right now, so I stick with Polycast and Plex G.
I've been tempted to try building a test tank to see how it goes, but got lotsa other stuff on my plate at the moment.

James

 

[aryth]

James, your are scaring the pants off me.
What exactly do you mean by

... The joints just fail, catastrophically....

Does it develop a big leak along the seam, or the whole tank bursts? I actually have difficulty imagining the tank, braced at the top bursting, which would imply seams failing all along the perimeter. But, if this is the case.... I hope I will not have nightmares after building, or indeed having any tank of this size.

 

[Floyd R Turbo]

It's the nightmare scenario. A seam will just peel apart from one end to the other, typically the bottom seam, meaning the "blowout" scenario.

 

[aryth]

Would(could) the 2-parts glue/gluing method be a better option in this case?

 

[Floyd R Turbo]

2 part is not really any stronger. James explains it best

http://www.reefcentral.com/forums/showthread.php?p=24321624#post24321624

 

[aryth]

Guys,

I got a quote on polycast at twice the price of chemcast (from the same place). Does it really worth it? Basically my dilemma is either to take the risk and overbuild the tank with chemcast (thicker walls, reinforced seams, etc..), or bite the bullet (...and moonlight somewhere for a couple of month).

What would you do?

 

[Floyd R Turbo]

Thicker chemcast is still chemcast

I would get a quote for Plexiglas-G

Polycast is top quality and also it is imperial thickness, meaning 1/2" is 1/2" and not 0.472 (metric equivalent = 12mm) or 1" = 1" not .944 (24mm) so there is a slight advantage there. But like you said, super $$

 

[aryth]

It's the nightmare scenario. A seam will just peel apart from one end to the other, typically the bottom seam, meaning the "blowout" scenario.

Would a shallow rabbit joint at the lower seam be a crazy idea? I don't really care about appearance there as it will be covered, only integrity.

.. the rabbit with the lip on the inside of the wall-piece.
.. and probably only on the long, side walls

 

[OhMatic]

Working with mirror acrylic.?
Could I bend/melt mirrored acrylic into a cylinder or half cylinder?

 

[aryth]

Alright, just placed the order. Chemcast it is!
Just could not get anything better in reasonable time (not even considering money). The choice has become whether to do the tank at all - and I was waiting too long to get back into reefing, to pass again... (besides, after all James did for acrylic DIY-ers, I will be happy to be his Chemcast guinea pig)

Thanks a lot all, and especially James and Floyd. I've red this thread from beginning some times (years) back, which gave me confidence to do a project like this, and discovering recently that it is is still alive and VERY useful is a tribute mainly to you.