So the build is in motion again. At last!
Progress has been painfully slow for a good while, the cure/kure/crap leaching out/whatever you decide to call it, for my diy rock seems to just be going on and on, but that's another story..
I've finally gotten around to cutting up the back of the tank and building an external overflow box. It's 1//4" glass as it's not going to be holding much water anyway. The rest of the glass in the tank is about 3/8" I think.
Anyway, the cutting of the tank went OK for a first attempt I guess. I was determined the the water level will be above the bottom of the top trim so it's not visible (if that made any sense), so I cut the trim back. To do this I marked everything out carefully and then used a large (wood) hole saw to drill a hole in a piece of plywood, which I used as a guide to start the hole bit in the plastic trim. I then positioned this so the saw cut a nice semi circle at each end of the bit I wanted to take out of the trim. I used the mandrel for the hole saw back to front to avoid having the pilot drill bit sticking out. Then it's just a matter of drilling carefully until you get to the glass.. From there I used a cutting wheel (for wood again) to join the tops of the semicircles. It would have been fine to just cut out the trim square, but I'm just like that..
I then used a 3/8" diamond drill bit to cut four holes (one at each end of both slots) and then a 2" diamond cutting wheel to join them up.
I noticed something that may be of interest to others in this process. I intended to use a dremel clone to do the majority of the cutting (not the drilling) because I thought it'd be the best way to do it. I was wrong. The cutting wheel on the 'dremel' was not really a success. Since it was one you screw the blade onto the shaft, there is always some whirl to it. At low speeds the 'dremel' has no torque and stalls if you apply any amount of pressure, at high speed settings it whirls and chatters like mad until you press down then the 'dremel' itself overheats. Maybe this isn't an issue if you have a real dremel not a piece of crap imitation like mine, I don't know, but it was pretty much only good for cutting the first very shallow track in the surface of the glass as a guide. I then found it far more effective to put the wheel in the drill and use that. With the extra torque of the drill, you can press harder (back off the pressure before you break through of course) and actually cut the glass faster than your beard grows.
Also, if you cut in such a direction that the wheel is coming upwards at the forward edge as you cut along it also helps reduce any splintering of glass. I found it best to do the cut in a number of passes.
After that I set to work on the overflow, which is when crap started really going wrong!
I already had some glass from when I was replacing the back of the tank as I bought a panel of the wrong thickness the first time around. No problem, I'll use it for the overflow. Now let's just say there are some things in my opinion best left to those who know how - flying jumbo jets etc. Let's just say that cutting 1/4" glass has now been added to that list.... If anyone has a use for a large number of irregularly shaped bits of 1/4" glass, let me know.
So if you don't succeed, try again, and if you still don't, give up because there's no point making a fool of yourself.. I went to the glass shop with a list of measurements...
A few days later I drilled three 1 3/4" holes in the bottom panel of the overflow and stuck it all together.
One point to note is that when I put the new pane in the tank, I stuck stuff in place with masking tape. This time I used Tuck Tape because it sticks like you know what to a blanket. Unfortunately I hadn't thought about the fact that being plastic, it stops (pretty much)the silicone underneath it from setting so you have to take it off then wait another day. Finally it leaves behind bits of red adhesive when you take it off. This does come off with gas, but you then stink out the laundry room and have to run the ventilator full throttle for a couple of hours to get the smell out of the entire house BEFORE the wife comes home...
I've also resealed the tank for the sump. I ended up doing it twice because I ran out of silicone the first time. By the time I got some more the first lot had half gone off which meant it lifted with the masking tape so I had to scrape it off and do it again. Lesson, always have more silicone in hand than you think you'll need. No Photos of that yet because it's not got any baffles or anything yet so it's a bit boring..
Rob.