Reef nutrition

Taking a Jigsaw to an Acrylic Tank

GDawson

GDawson

Guest
BARcard
I have an old style TruVu 125g tank that I'm eyeing as a FOWLR. Because its older the openings on the top are the very small and narrow. Can I use a jigsaw or something similar to open up the top or would it weaken the structure too much?

-Gregory
 
If you beef up the bracing you can do it, stock tanks don't use the thickest of tops, so cutting into it means you need to reinforce what will remain, whether it is to thicken the center brace or do a perimeter brace depends on how you want to cut it.
 
So leave a margin around the tank and thicken the center, left, and right braces with another piece of acrylic. Just lay it on top and use the liquid weld stuff? Does it need to wrap over the top and hug the top portion of the front and back panels?

-Gregory
 
Out of curiosity why would you want to make the openings bigger? Only reason I've ever done that (with bad results :D) on acrylic tanks is because I wanted to get a beefy (halide) light over that area.
 
sfsuphysics said:
Out of curiosity why would you want to make the openings bigger? Only reason I've ever done that (with bad results :D) on acrylic tanks is because I wanted to get a beefy (halide) light over that area.
Click to expand...

1) you can't put LR of any size in the tank
2) you can reach into the tank without removing the canopy and using a ladder/step stool
3) once you can get into the tank you can't bend your arm/reach the bottom 1/2 of the front'side/back panels to clean (yes I have short arms...not T Rex short but close....)
4) you can't reach the bottom
5) to do anything in the tank is just a PITA

These are all reasons it's not been filled as of yet.....if cutting the openings larger is not a reasonable option I'll have to go fresh water with it. As a fresh water tank it's a waste 'cause it already has an inside corner overflow and durso stand pipe to a sump and skimmer. Really can't do a reef with it 'cause I can't get to all the inside surfaces to scrape the coralline.

-Gregory
 
Cutting larger holes is reasonable, however as Jeremy said you want to reinforce what you do. If you leave a center brace however that will go a huge way in keeping it more stable (also something that's a good place to reinforce).

Also I'm more happy about using a circular saw to do most of the cutting, combined with a hole saw/large(ish) diameter drill at the corners so you don't have square corners.
 
sfsuphysics said:
Cutting larger holes is reasonable, however as Jeremy said you want to reinforce what you do. If you leave a center brace however that will go a huge way in keeping it more stable (also something that's a good place to reinforce).

Also I'm more happy about using a circular saw to do most of the cutting, combined with a hole saw/large(ish) diameter drill at the corners so you don't have square corners.
Click to expand...

Good info...thx! Yes I'll leave a nice thick center brace, no prob. I'll just make the existing openings wider/deeper not longer. The cuts will only come forward. The back portion won't be touched.

Now does anyoine have a good reference for gluing/welding acrylic I can study?

-Gregory
 
Gluing is really quite easy, to simplify things use Weld-on #16, you can use the #4, but to get a clean bond with no bubbles you need a little experience so I'd forgo that.

Acrylic tempers with time and adhesion becomes a little tricky, I suggest you rough up the top with a little 320 grit, just enough to haze the top up. Use one long piece of acrylic, get 1/4" thick or thicker, glue and clamp.

If you really wan to be trick, you can brace the sides too, make sure you add small pieces a the joints that overlap.
 
Minor detail : Suggest adding braces and strengthening FIRST, before you make the cuts.

I have used a saber saw myself, and it generally works ok, but the blade gets hot fast, and once it does, it
starts to melt instead of cut, and turns into a big mess.
Make sure to squirt a tiny stream of water constantly.

A router is the best way though.

I actually use both.
Saber saw to cut to about 1/8" of where you want to end up.
Then clamp on a board, for a simple router fence, and run the router on it to clean it up.
 
+1 on the router. I would glue the new braces on to the size you want the new openings and then use a flush trim router bit to cut it. A saw of any sort is just going to make a mess. All the tops on acrylic tanks are cut with routers when they are made by the manufacture. That's how they get nice clean cuts.
 
Good it can be done. I was getting a bit worried there......

I'll photo the progress and post in DYI in case others need to do this also. The openings on those older tanks really do suck.

-Gregory
 
How old the tank is may come into play. I've tried to use a jigsaw on an older acrylic tank (one that has been baked over lights) and the acrylic was so brittle it broke in larger pieces and cracked where it should not have cracked.
 
The tank is almost 20 years at this point.....however, it's been empty at least the last 10. Before that there were only T5s on close fitting reflectors that sat directly on the two openings. I don't believe that the top has been exposed to any lights.

-Gregory
 
Even time will do the same thing as UV, careful (wear protection). Gluing a tank that old will pretty much guarantee some crazing. Do not use the liquid (#4) glue on an aged tank.
 
"Crazing" is small cracks you get on the surface.
It is caused by buildup of internal stress in the acrylic, especially around cuts and openings. Over time, especially with UV light,
these stresses can cause lots of tiny cracks at the surface.
A solvent, including acrylic glue like #4, can really trigger the formation, since it loosens the polymer bonds.
While a bit ugly, micro-cracks are not usually a problem.

If you want to see it, take an only piece of acrylic, and dip in lacquer thinner. Should show up on the edges.

The complex way to reduce that is "Annealing".
Where you heat the acrylic to about 180 degrees, and slowly cool. Eliminates the internal stresses.
I have heard of people using boiling water in a big tub for several hours.

Another idea is to use weld on #40, and glue pieces above/below the area of concern.
Since that is more resin, less solvent, supposedly less likely to craze when used.
 
Crazing in a 20 year old tank can be structurally damaging especially given what he wants to do with it. The top is where most of the strength of a tank comes from in an acrylic tank.

And good luck annealing a tank that size :lol: If you do please take pictures :D
 
rygh said:
Another idea is to use weld on #40, and glue pieces above/below the area of concern.
Since that is more resin, less solvent, supposedly less likely to craze when used.
Click to expand...

If you use #40, mix by weight, not by volume similar to casting epoxy.
 
OK this is starting to sound a bit more complicated than anticipated. I guess the questions are:

1) Is this really worth doing to a tank this old?
2) If done by an amateur (me!) is there a chance that I'll just de-stabilize the whole structure and come home to a mess one day?
3) If I just leave it do acrylic tanks have a life expectancy and should I just replace it?

-Gregory
 
You must log in or register to reply here.
Back
Top