75-gallon complete re-seal?

[arohead]

Good day,

After a search, I decided to post this as I did not feel any previous post was thorough in addressing the question I have.
I recently acquired a 75-gallon tank. Upon arriving home, I could see that the sealant was pulling away in the corners, and fairly large bubbles were present between the glass and sealant, and decided to reseal the tank. I carefully removed the fillets, and discovered that the seal between the bottom plate and the sides were not tight. Slight pressure on the plate caused the water between the plate and the bottom frame to move. I do not trust this tank with just water in it-let alone with pump, heater and living residents.
My question? How does one go about resealing a tank from scratch? I know the sealing surfaces must be perfectly clean, but which solvent will safely remove the silicone residue that does not come up with a new razor blade? When cleaned, what is the correct assembly procedure, and what can be done to hold the plates in place while the silicone cures? What is the proper squeeze-out (how much sealant should be between adjoining plates)? If the silicone skins quickly, it seems that once this is begun, it should not stop until complete, from initial assembly to final fillets to assure good contact with fresh sealant.
This tank apparently had none of the center bracing that I've seen on the top frame of 50-55 gallon tanks.
The top frame is quite encrusted with salts. I pulled off rather easily. Depending on how difficult it is, I may clean the glass groove with steel wool and a little solvent for ABS ( I think that is what the frame is made of), hopefully the new sealant will have a much better bite than the last job had.
My wish is fish. Fish are my wish. My little monsters that have conquered their 29-gallon would have liked to move into this the day I brought it home.
It's as big as I can offer them at this point, and I would like to get the 75 rebuilt safely the first time, as soon as possible.

Thanks for any help!

arohead

ps what about a sticky on this? Should we MFK'ers not all be able to access a definitive description of the process? Isn't there always a larger tank just around the corner waiting to be completely re-sealed?

 

[terd ferguson]

Rubbing alcohol and continued scraping are what was described to me to completely remove old silicone.

The correct assembly procedure is to secure the back glass to the bottom first. Then one small side, then the other small side, then the front glass.

Most people say to put tape down to hold the pieces in place (that and your hands). The silicone should set up fairly quickly. The entire process of putting a tank together has been described to me to take about 10 minutes. I assume once you get the pieces on, they hold each other up. I imagine a helpful friend would be beneficial during the assembly process.

I am still unsure of the "squeeze out" you are talking about (I understand what you're talking about, but don't have the answer). I'm about to do the same thing with a 190 and am curious to hear what others say.

For a top brace, you can have one or two pieces of glass cut the width of the tank and silicone them at the top (where a center brace would normally be). They must be exactly the same width as the top of your aquarium.

I hope I've been of some help and am looking forward to hearing what other say. Like I sadi, I'm about to do the same thing on a 190. I think a sticky on this topic would be a great idea. Good luck.

 

[terd ferguson]

You may or may not find some useful information in my thread similar to this one...

http://www.monsterfishkeepers.com/forums/showthread.php?t=90455

 

[arohead]

Good eve,

By "squeeze-out", I am referring to the amount of sealant remaining between panels after assembly. At one time in centuries past I was a sealer for fuel cells on commercial aircraft. When parts were designed to be joined with sealant in addition to mechanical fasteners, sealant was applied before the parts were joined, the fasteners brought to torque spec., and excess sealant removed while still very uncured. The expectation is that there will be no voids in the sealant (causing possible rupture of sealant with changes in temperature or pressure). The mechanical fasteners (bolts or rivets) assured the parts remained in place. In joining glass plates, I am relying on the strength and adhesion of the sealant alone to prevent leaks. There must be some sort of ratio of glass to sealant that is most effective. Of course, any voids or bubbles in this sealing plane simply indicate there is absolutely nothing holding the tank together where they appear. It seems that the design of these tanks rely on the silicone to distribute the load evenly. I would not sleep well with the image of voids between the plates. Which this tank does have, running from 3" below the top to 5 1/2" below. In this location, only the fillet applied over it will be doing the work of sealing, plus the mechanical strength of the non-existent seal between the plates.
I found a residue of reinforced tape around the top of the plates at the corners, more than likely this held them in place as they were assembled, and the top frame applied. I like that idea as that tape should resist stretching fairly well.
I used a silicone-based sealant in aircraft wings- and when sealant needs to be repaired on the plane, the area is solvent cleaned, the damaged area of sealant removed, then the remaining sealant is "roughed-up", like patching an inner tube, before sealant is reapplied. Seems to hold on aircraft- I wonder how it works in fish tanks? Anybody want to try an experiment?

-arohead

{INSERT STANDARD DISCLAIMER HERE, NOTIFY READERS OF INHERENT RISKS, ENCOURAGE PROPER USE OF SAFETY EQUIPMENT AND DISPOSAL OF WASTE. ADDITIONALLY, GO ON TO IDENTIFY ONE'S SELF AS LESS-THAN-A CERTIFIED, FULLY-TRAINED AUTHORITY IN THIS AREA, AND, FOR CRYING OUT LOUD, FIND A MUCH SMALLER, HIGHLY ILLEGIBLE FONT IF YOU WISH TO CONTINUE INSERTING DISCLAIMERS IN YOUR POSTS!!!}

 

[terd ferguson]

Like I said, I understand the theory, I just don't know the answer as to how much silicone to use. My main concern with my reseal is that a piece of 1/2" thick 60"x30" glass is very heavy and would squeeze out most of the silicone not leaving a good seal. I'm sure I'm overthinking this though. I mean, they don't use shims or anything like that when building glass aquariums (at least not that I'm aware of).

As far as your aircraft wing repair method of roughing up the silicone rather than removing it, I doubt you'll find anyone willing to risk trying it. The thought of 190 gallons of water rushing out onto my floor is the stuff nightmares are made of.