Acrylic frag tank welding help!

[spankege101]

I am looking for some feedback on the first acrylic tank build. Dimensions are 24x18x10, which is around 25 gallons of water. I prepped the joints with sanding method and was sure everything was smooth. The material I used was 3/4 in cast acrylic that was cut by my local dealer.

My issues is with the welding. I laid out everything. Checked and double checked. Taped everything together started with the front section and worked my way back. The bottom seams are perfect and couldn't be better. The issue that I found and what I am not happy with is the 10in seams on the sides. It looks like towards to top of the pieces. They started to flare out a bit and caused about 60% of the acrylic to be welded. I am sure it will hold water but am not happy with the outcome. In some sections I am going to go back and use more Weldon 4 on those spots to create more of a bond. I will post pictures of the seams when I get home.

What I am asking for is some feedback on next steps. Should I use Weldon 4 on the seams again? Or should I use Weldon 40 only on the top end of the seams. I was also thinking that I could use more 3/4 in acrylic and just go over the corners and re weld them. Worst case is that I have to redo the whole tank. So I would like thoughts on adding more sealant or actually redoing it and the steps in doing that. I am not really worried about how it looks as it will be used strictly as a propagation system. Thanks for any feedback.

I will include a picture of the whole project as it sits together. Like i said already I will post pictures of the seams tonight.

 

[Triggreef]

Looks good from the pic. If your worried you could use some Weldon 16. After Weldon 3 though those seems are absolutely stronger than the material itself. I've tried to break apart old ones I made and you just can't break that seam.

Can you see bubbles etc in the seam? If not I wouldn't worry.

 

[spankege101]

Yeah there are some bubbles near the top. It is still a complete seam. I over did the thickness of acrylic for the volume of water. Not sure if that makes a huge difference.

 

[Jlobes]

Yeah there are some bubbles near the top. It is still a complete seam. I over did the thickness of acrylic for the volume of water. Not sure if that makes a huge difference.

bubbles are bad. Also, how can it be a "complete seam" if only 60% of the material is bonded?

How did the pieces get out of place by 40%? what were you using to keep things in place? what method of bonding did you use? I wouldnt feel too confident in that tank, but thats just me. Honestly, I think you mightve fudged the order of operations for bonding the seams.

 

[spankege101]

The bottom seams are perfect and complete. It's like a weld for the top there is a complete weld but it does not fill the entire 3/4 in of the acrylic. I will take a picture to show you.

Do you have any advice on how to fix it or redo the seams? First project I have done so it's a learning curve for me.

 

[spankege101]

Here are the seams

How is something like that fixed or repaired? Thanks

 

[Pepcrylic]

Looks like your seam was starved for solvent . If that is a 25 gal. tank and built with 3/4 Plexi-G it shouldnt have a problem holding water. To fix the unsightly seams you will have to cut the tank apart and start over. Can you explain the steps and methods you used to weld the tank together?
You might want to place a euro-brace on the seam starved tank for a bit of insurance .

 

[Pepcrylic]

BTW The "Sanding Method" for prepping an acrylic edge is not good practice. That method is probably part of the reason your seams resulted in very bubbly edges. It is recommended to use a router to prep an edge. When you use a sanding block it is very difficult to remain at a 90 deg's to the face. If you are off just a few degrees you will not have a true flat surface.

 

[Lowell Lemon]

You just discovered the problem with control on the sanding method. That is why most professionals do not sand anymore...we have all had the problems you showed. You need to set up a carbide bit route with a fence. The fence should be cut square on a properly set up table saw at the least. The idea is to cut about .200 of an inch off the first half of the fence and leave the rest .200 of an inch wider. Next you make a cut or drill a hole larger than the router bit between the two areas of the fence. Clamp the fence to a table with the router mounted from below and the bit between the infeed (narrow section by .200 of an inch) and the out feed (wider than the infeed by .200 of an inch. Using a quality straight edge adjust the infeed side until it is absolutly even with the largest flut on the carbide blade. Make a test pass with some acrylic scrap. The infeed should not allow the acrylic to cut more on the front of the pass than the back of the pass. If you notice more material cut in the front of the pass you need to close the distance between the infeed and the bit. If you notice a small area on the end of the cut where more material is removed you need to open the distance at the infeed and the bit. This is the same as using a joiner table with carbide knives to make a smoothe square edge on the acrylic. Either method will work. If you need pictures let me know or check out the fabrication thread Acylic Fabrication Q&A on this forum.

 

[spankege101]

I will investigate. I would be interested to see how yours is setup. I am just nervous about using a router on the expensive acrylic.

 

[Pepcrylic]

There are other methods to use the router to prep the edge.
I cut a templet out of OSB and use a spiral flush trim bit.
With this method you do not need a router table.

 

[Lowell Lemon]

This is what I use for a router fence to edge the acrylic before bonding the seams. It is over 4' in length. One well used table as you can see.

 

[spankege101]

I appreciate that pic. I do have a router table. Just need to make sure it's level and I don't take off to much of the material

 

[Lowell Lemon]

A close up of the router bit and and the in feed side is about .200" less (Right side) than the out feed side. Made out of 1/2" cell cast acrylic. Two flute solid carbide router bit ground just for acrylic. Purchased the router bit from FTM Plastics on line.