weld on but-joint?

[reefermike1]

really cool find today at work. an old pallet up on the shelf with im guessing 300-400, 1/4" x 6" x 6ft of black acrylic strips. the story goes some guy that used to work there aquired it somehow and brought it there for some project that never got done. this was 10 or so years ago so i was told take as much as i want, preferably all of it if i have a use for it. i immediately thought of coast to coast overflow boxes. the only thing is they are only 6" wide so anything wider than that would have to be 2 pieces glued togeather lengthwise(but-joint). so my questions are if i used weld-on would the seam always be the weakest point? how hard would it be to make it watertight along that seam? and how visable would it be on black acrylic? another good question for those with ctc overflows is how deep should it be? would 6" be sufficient for internal or external overflows? keep in mind theres ALOT of material available free to me and i could make alot of them any size up to 6ft long!! also i have access to cnc machines that i could easily program to cut perfect edges for glueing and slots for the surface skimmer part, with a .250 ball nose endmill i could cut 48 6ft lengths at a time!!

[Fly Guy]

6" is deep enough for a external CTC. Thats how deep mine is. Although I will say that the next one I do will be 8.

Glued correctly, being water tight and the strength of your seams if you were to glue them together is a non issue, although 1/2" (or more) thick would really be best for external overflow boxes longer than a couple feet IMO. You could glue them together and fix that though. Being an external box behind the tank........the fact that you may be able to see the seams a little is kind of a non issue as well. If cut smoothly and glued well, the seams would show up less on black acrylic that they would clear anyway.

[RobinsonFam1]

overflow boxes have very little pressure on them due to the fact that they typically have a similar water content inside as outside which equalizes the pressure.
depending on how long the tank is you could always add supports inside to prevent any flex.

[Fly Guy]

Originally Posted by RobinsonFam1

overflow boxes have very little pressure on them due to the fact that they typically have a similar water content inside as outside which equalizes the pressure.
depending on how long the tank is you could always add supports inside to prevent any flex.

That is true when talkingabout an INTERNAL overflow box. Not true when talking about an external which is by far the best way to do it. Nothing in your tank to look at, or more importantly, impede flow.

Just the same...if attaching tho the outside of a acrylic tank, and braced it..............1/4" would probably be enough......I just wouldnt do it with less than 1/2" myself.

[reefermike1]

would i be able to weld on 2 pieces togeather to make a 12" piece?

[woz9683]

You should be able to, but it's pretty tough. I tried it out on some scrap just to see how it would look and it wasn't half bad. The problem with using weld-on 3 or 4 is when you drop the two pieces together there's nowhere for the acrylic/solvent to puddle so the excess runs down the face of the project. Looks pretty nasty at first but you can polish it after it cures to fix that.

You're probably just going to have to test it out multiple times to see how it can work. Black will look better in the end because you won't be able to see any bubbles in the seam, but it will also be harder to tell if the joints will hold water. Maybe using a thicker weld-on like #16 or #40 would be a better choice. Then you could work with the two pieces next to each other instead of vertically.

[Tasher80]

If its not seen at all then any drips wouldn't matter correct?