Acrylic Tank Assembly - Weldon 4 vs. 40

[RandalB]

Hi all,
Getting set to assemble my first tank, got all the prep work done and getting set to glue. The local acrylic guy is telling me the way to go is with Weldon 40. It's the 2x part cement that fills in cracks and gaps. He tells me that it will form a stronger bond than 4 and be safer in the long run. I have both, what do you guys think is the best way to go?

Anyone have experience with using 40? Feedback?

Thanks in advance,
RandalB

 

[otto486]

Ive never heard of 40, but anything that is 2 part seems... like a pain in the rear. Weld-on 3, 4, and 16 are about the only ones that are really needed in the aquarium hobby. The only reason you would need a crack filler is if the joints got buggered somehow. If you get a really thourough bond, and make sure that you sand down the edges of the acrylic to be REALLY smooth (start with a course sandpaper and get finer and finer as it smooths... unless you have a table router). The smoother the edges, the better your chances for success.

If you haven't, check out Marc levenson's website, melevsreef.com That is the best single resource that I have yet found.

Also, the differences between 3,4, and 16:
I use 4, it is fairly quickly drying, but doesn't form as strong of a bond as 3, which takes longer to dry. 16 is just a good backup for small/patch jobs, and doesn't create a strong joint, but is very easy to work with.

I could be confused with 3 and 4 on which is stronger, but the differences aren't that big. Marc Levenson uses 3 (well he suggests 3), I use 4.

 

[rottface4]

I have never used 40 but its is prefered when building a tank (over 3,4). It is stronger and you get a better joint. It is not absolutely neccessary to build a tank. It is also more difficult to work with, and I believe there is a special applicator gun then can be used to help apply it.

 

[hebygb]

I have been working with acrylic for over 20 years... The best bond is formed when your edges are perfect, and sit flush when dry. If you have gaps, then you haven't done your prep work well. you also want a smooth edge... any deformities will challenge the bond and could result in crazing. If the edges are dead on.... then you will find that the thinner solvent will "run" right along the edge without need for straight pins. This capillary movement of solvent means that you have properly prepped your edges.

 

[miwoodar]

The post above is discussing the use of WO4 which is what I just used. There are a number of good threads that discuss using WO4. I don't know of any that show a step by step with WO40 (WO42 is the same thing but comes with an applicator). WO16 isn't often recommended for tank construction but can be very handy for things like skimmers and reactors. WO3 is a faster version of WO4. Don't use WO3 unless you are *sure* it is right for your situation because you've done a lot of homework that points you in that direction.

http://www.reefcentral.com/forums/printthread.php?s=&threadid=390652&perpage=497

http://www.cichlid-forum.com/articles/diy_acrylic_aquarium.php

http://reefcentral.com/forums/printthread.php?s=&threadid=1023094&perpage=303

If you have a LOT of extra time...look at this one too:
http://www.reefcentral.com/forums/printthread.php?s=&threadid=96763&perpage=2165

 

[Acrylics]

Hmm,
Is 40/42 stronger? *potentially* but water-thin solvent joint's strength run at >2000psi. If your tank ever even gets close to that, then 40 might be necessary but that's waaaay out of the league of normal aquaria. IMO the only time it's really necessary is when working with material >2" thick at which point cutter flex becomes problematic so edge prep is a PITA. 40/42 is recommended and used most often when you can't get your edges prepped properly, using thicker material, or doing miters.
As for better in the long run, hmm I've got tanks in service for ~20yrs, IMO that's long enough to call it good

HTH,
James

 

[miwoodar]

For reference...my tank will be less than 1psi at the bottom.

1369 square inches of footprint
1162 lbs of water

 

[hebygb]

acrylics - when working with material that thick, isnt it better to use laser cuts? And because of this would not edge prep be even easier (no cutter flex)? I have found that when people use a heavier solvent, they are relying on it to fill gaps or make up for flaws, and tend to float way too much between the surfaces. This makes for a poor bond that may not fail until later down the road. You are the expert in this area ... I am just a practioner.

 

[Acrylics]

Lasers refract in the cut, so they kinda "fan out", leaving an angle on rather than a straight and square cut. Secondly, lasers tend to heat the acrylic and this *can* lead to crazing. In recent yrs lasers have become better but try laser cutting 1.5" and you'll see what I'm yakkin' about

Theoretically, you should be able to float a nice thick (1/8") layer of 40 in the joint but there's still the matter of how much "bite" the 40 has in the acrylic. The 40 still has to stick to it to hold a bond, and this amount of "bite" varies from acrylic to acrylic, batch to batch, how old the 40 is, what size batches it is made in, and how the 40 is prepared.

You're right though, heavier cements are for gap filling and making up for flaws. 16 can do this to a very minor extend, 40/42 will work much better, but the best way is to have the edges properly prepared to begin with.

James

 

[RandalB]

Thanks for all the info guys,

So no real point in using the 40 on .5" Acrylic unless I can't get 4. Is 40 a real thick solvent like 16?

RandalB

 

[Acrylics]

40 is an actual acrylic resin and is thick like maple syrup, thicker actually.

James