Acrylic fabrication questions? I can help!

[aryth]

Another question (likely one of many coming...).

What would be acceptable deflection of a stand under acrylic tank (250 gal, 1" walls, in my case)? ... and if you want to be absolutely conservative?

I did rough calculations and came up with deflection of up to 1/32" on 4' span for my stand. Is it something you would be comfortable with?

Thanks,
Andrey

 

[Floyd R Turbo]

That might be a better question for the RocketEngineer thread (stand template), or is that where you originally asked it?

 

[aryth]

I could not find exact info there, but you are right, I will ask.
The acrylic tanks are more flexible than glass, and if I understand correctly (I think James said it somewhere), eventually take shape of whatever they stand on. I was hoping to know if there are any standards/rule of thumbs/best practices for deflection or flatness of the support or tank's bottom.

 

[Floyd R Turbo]

Well the goal is no deflection, of course that's not reality. The question is, based on your stand design, what will the deflection be under full load? That is a RocketEngineer question, definitely

http://www.reefcentral.com/forums/showthread.php?p=24468388

 

[aryth]

Well the goal is no deflection, of course that's not reality. The question is, based on your stand design, what will the deflection be under full load? That is a RocketEngineer question, definitely

http://www.reefcentral.com/forums/showthread.php?p=24468388

In my case it is the other way around... I believe, I can design the stand to have any deflection I want. The question is what the actual deflection number I should aim for (RocketEngineer has 1/8" per 4' - that is a start). I.e, is there any (official or unofficial) engineering standard for this, and then how conservative one would go with less than ideal tank material.
At the end it is all about trade-offs (weight, ease of access, price... roughly in this order for me now)

 

[Acrylics]

I have a 125g acrylic tank with acrylic stand and hood. I love the tank and stand but the hood has always been an issue. It is only 6" tall so they lights are right on top of the water with no spread.

I made a 14" high wood hood and attempted to make a front door but being made out of wood it looks terrible. I want the front panel to be black acrylic like the rest of the stand.

What are good sources? The sheet needs to be 60.5 x 14 3/4. I plan to attach it to a wood frame which will attach to the front of the frame I have in the photo below.

I can't recommend specific sources, but I'd guess you're as well off buying locally. By the time you pay for shipping and all - probably about the same cost. Probably expect to pay $7/sq ft or so? In your case, I'd look at the cheaper cast import materials.. likely to serve you better

HTH,
James

 

[Acrylics]

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

Very crazy, to be honest. You'd be increasing the overall stress greatly by doing so.

HTH,
James

 

[aryth]

Very crazy, to be honest. You'd be increasing the overall stress greatly by doing so.

HTH,
James

Thanks. I have settled on doing the traditional glue up and reinforcing the bottom seams with 1/2"x1/2" rod inside all along the perimeter of the bottom.

 

[guserto4]

Back on page 109, post 2709, there was some discussion about general purpose P- max vs. plexiglas G. The recommendation was to never use gen purpose P-max for a display tank: This had nothing to do with quality and everything to do with clarity, right? I mean, if it's not good enough for a DT but it is good enough for a sump, which could ruin the system if it broke just like a DT break would, right? Is there some other reason I shouldn't ever use p-max if I'm trying to save a buck on my own 80x24x16"T build?

 

[Floyd R Turbo]

PMACS basically comes off the same line as Plex-G, but it has flaws: out of tolerance (thickness, etc) flecks of discoloration, imperfections in the surface, etc. Personally I've never seen a difference.

Keep in mind that Plex-G can have this as well (I can personally attest to this), the difference is there is a warranty on Plex-G. But that warranty is as valuable as dog feces in a box to someone who purchases less than $100K per year, because the minute you cut the material, the warranty is void...unless you purchase $100k/yr from them. Then they will repay you for time and material for replacing the tank if you unmask it when it's done and find a critical flaw.

 

[Acrylics]

The primary difference is that P-Macs has no inspection done, no warranty, there could be anything in the material and thickness can vary more. It may come from a "bad batch" or whatever. No warranty doesn't bother me, but I have seen a good number of flaws in the material and have had a coupla things rejected because of particulate matter embedded in the material - before I knew the difference. Yes, Plex-G can run thin and does get flaws, but far fewer and at least *has* been inspected.

For sumps, I see no problem using P-Macs. But anything in a display/viewing area - nope.

James

 

[pandimus]

PMACS basically comes off the same line as Plex-G, but it has flaws: out of tolerance (thickness, etc) flecks of discoloration, imperfections in the surface, etc. Personally I've never seen a difference.

Keep in mind that Plex-G can have this as well (I can personally attest to this), the difference is there is a warranty on Plex-G. But that warranty is as valuable as dog feces in a box to someone who purchases less than $100K per year, because the minute you cut the material, the warranty is void...unless you purchase $100k/yr from them. Then they will repay you for time and material for replacing the tank if you unmask it when it's done and find a critical flaw.

Think the non labeled plexi is pmacs? I was told it was plexi. It's 3/8 clear and white. Obviously the 1/4 white is chemcast. The 1/4 is for the Euro bracing

Sent from my XT1254 using Tapatalk

 

[Acrylics]

Think the non labeled plexi is pmacs? I was told it was plexi. It's 3/8 clear and white. Obviously the 1/4 white is chemcast. The 1/4 is for the Euro bracing

no way of knowing with certainty from a pic. Lotsa companies sell plastic wrapped in a plain brown wrapper and lotsa people call all acrylic "Plexiglass" - even those in the industry. That said, if you're confident in your supplier that it's the "generic" Arkema or P-Macs, then it's more than likely gonna work just fine

James

 

[guserto4]

Thank you, gentlemen, for the further explanation. I imagine since I'm ordering 1 sheet in white and 1 in clear (going for that surgical, clean modern look on the bottom and back) the idea of actually envoking some sort of warranty is unlikely and I'm running the risk mostly on just the clear...

 

[pandimus]

no way of knowing with certainty from a pic. Lotsa companies sell plastic wrapped in a plain brown wrapper and lotsa people call all acrylic "Plexiglass" - even those in the industry. That said, if you're confident in your supplier that it's the "generic" Arkema or P-Macs, then it's more than likely gonna work just fine

James

I'm definitely confident. He is one of the bigger manufacturer in socal

Sent from my XT1254 using Tapatalk

 

[guserto4]

Hey one more question then as far a general purpose vs. plexiglas-G... Does P-macs glue up fine? Like for sumps it's cool, so I imagine it will hold water... Correct?

 

[pandimus]

Another quick question, there were some pictures, I believe on this thread that had the build order of a sump. does anyone have a copy of those or can provide me? I saved them on my phone, but lost them in a format..
:debi:

 

[pandimus]

Also how are you guys doing this inset for sock to sit in?

 

[pandimus]

Floyd R Turbo, Acrylics, and dattack. Thanks so much for the advice.

Floyd R Turbo, I read your old posts (#10 "“ in response to Chopper320's post, #4022, #4024) . The build order makes so much sense now. Would have been a nightmare to weld a horizontal and a vertical seam at the same time using weld-on #4.

My worry now is about getting everything square so that when I flip the sides/Euro brace assembly onto the base, that I don't have gaps. I plan to be as careful as possible, but do you have any tips?

All the panels will be machined using a CNC router so I expect to have good starting material, but how do you manage to get the edges aligned perfectly while racing the clock to pull the pins and remove air bubbles?

Nevermind first question. I quoted on them before.

Are there any specialized tools that you recommend?

I've searched the internet and have found some videos, but they all seem to be from non-experts using the capillary action method. Have any of you ever made a tutorial video or do you have a good one to recommend?

Seems like you must get asked these questions all the time. Is there a sticky I'm missing?

Thanks again everyone!

 

[pandimus]

Sorry trying to post these pictures which was from my first question