Working with Weld-On 16 ?

[DiverDude]

I'm building a HOB sump and given this sucker will hold ~50lbs of water, I bought some Weld-On 16. I've only ever used the water-like stuff before and always clamp-up my pieces and then apply it when everything is as I like it.

With the '16' though, it appears that you have to apply a bead and then assemble which makes making a box quite challenging.

I know a number of people on here have used this stuff before -and more than likely built sumps and other 'boxes' with it.

Any pointers or should I just stick to the water-like Weld-On 3 ?

[whatcaneyedo]

I've been told Weld-On 16 is for filling gaps and fixing breaks so that is all I have used it for. If you're able to produce nice clean cuts Weld-On 3 will give you a much nicer finish.

[DiverDude]

I've had good results in the past with weldon-on 3 but I've never done a) anything this heavy b) anything that held water before so when I saw that weld-on 16 was 'high strength', I naturally grabbed some

[no_bs]

Instead of welding the piece that hangs off the tank, why dont you form it, then weld the box onto it. Just a thought, it will be stronger.

[DiverDude]

Actually, that's the plan. I'm making a box; there will be a cutout at one end which will be the spillway back into the tank and the whole box will hang on a piece that I will heat-bend into a U shape and then bond to the box part.

That will be plenty strong. In fact, I'm pretty sure that weld-on 3 will be fine for the box as well but I 'discovered' this thicker, and supposedly stronger weld-on 16 and bought a tube to try and thought it would be good for the box -until I found it was a gel and not a water-like substance.

[no_bs]

I have used the 16 to octopuss proff our acrylic tank, and it worked out fine. I found it to be a little more forgiving and just as strong, IMO.

[Funky_Fish14]

Please do not use Weldon 16 as a gap-filler. Basically, all weld-on 16 is, is a syrupy version of weldon 3/4. 3 and 4 only have a slight difference in set-times. If you are good with 3/4, its probably better to go with those for the seams. You can pull it off with 16 but as you said, it makes assembly more difficult. I use 16 if the joint is crappy (which is also going to be something not holding a lot of weight). I mean it works for filling minute little gaps, but dont rely on it to fill visible cracks. If you want to strengthen joints from the outside or fill gaps, use weld-on 40.

Cheers,

Chris

[DiverDude]

I spent some time in the shop last night messing with all this. First, I'm now pretty sure that I can't assemble the 5 pieces of the box quickly and accurately enough for weld-on 16.

Also, I took some scrap and bonded it with weld-on 16 and got a feel for how it sets-up. frankly, I found the Weld-on 3 made a better-looking joint (fewer voids in the joint).

Fortunately, I've got a good table saw with a fence and a blade that cuts plastics well so making fairly smooth edges isn't a problem.

I'll post some pictures when I'm done.