Plantman Posted July 28, 2005 Report Share Posted July 28, 2005 HI All i need some feedback as i think it should work. i have a small tank 2x1x1 feet. it has a hole at the bottom which is 3 cm in diameter. question: i should cut a piece of perspex (instead of glass), square shape (4X4 or 5X5 depending on space available) to cover the hole at the bottom glass. i will be very surprise if it crack and is there some thing else i may have over look. thank you for your though. Quote Link to comment Share on other sites More sharing options...
Bluetom Posted July 28, 2005 Report Share Posted July 28, 2005 i think it would work fine, there is always the possiblity the crack may 'spread' but I would say go for it. you an aways get a piece of glass cut to either replace or cover the bottom(from the inside) Quote Link to comment Share on other sites More sharing options...
Tanksman Posted July 28, 2005 Report Share Posted July 28, 2005 You definitely want to put the patch on the inside bottom of the tank to ensure the underneath surface stays flat - I would find a small piece of glass because it will be much stonger and will help stop the crack - hole spreading. Heaps of glass around and it's going to need at least a week to cure anyway so whats another couple of days :-? Quote Link to comment Share on other sites More sharing options...
Plantman Posted July 28, 2005 Author Report Share Posted July 28, 2005 Hi All thanks for the input. i am getting may 6 to 10 tank. i have heaps of perspex (6to 8 mm thick) whic i have access to machine cut. i do not want to spend more money as i already have. that is the reason for using perspex to patch the hole from the inside of the tank. i do not think the perspex will crack or anything. the temp of the water should be quite constant. what sort of silicon or adhesive should i use. any recommendation? thanks Quote Link to comment Share on other sites More sharing options...
Alan Posted July 28, 2005 Report Share Posted July 28, 2005 Plantman Don't be a tight ass. Go down to the local glazier and get a piece of scrap glass from their bin. DON'T use perspex Silicone doesn't stick to it. If you have glass lids, you could use that and use the perspex for the lids. The silicon to use, is acetic based, and hazardous to breathe in the fumes, it should read "Aquarium Safe". As it is just sitting on the base, once it has been smoothed off, you can fill it with water straight away. It will set under water. Alan 104 Quote Link to comment Share on other sites More sharing options...
Pegasus Posted July 28, 2005 Report Share Posted July 28, 2005 Ditto: Silicone doesn't stick to it. It sure looks fine for a while... but then peels off once it is set. The Silicone I use is Silaflex RTV Professional Range for Glass and Ceramics Clear type. Marketed by Fosroc and available at any decent hardware store. Bill. Quote Link to comment Share on other sites More sharing options...
Jo1 Posted July 28, 2005 Report Share Posted July 28, 2005 If you use a product called Primer No 9 (Fosroc) on the acrylic silicone will adhere but I wouldn't risk sticking the two products together either. Quote Link to comment Share on other sites More sharing options...
Alan Posted July 28, 2005 Report Share Posted July 28, 2005 Three strikes in a row Plantman. YA OUT!!! Go get some glass. Alan 104 Quote Link to comment Share on other sites More sharing options...
Plantman Posted July 28, 2005 Author Report Share Posted July 28, 2005 OK guys i guess i am one of those who like to try out new approach. may be the adhesiveness may not be strong between two different elements. thanks for the comments. i will cut the glass instead. Quote Link to comment Share on other sites More sharing options...
BK Posted July 28, 2005 Report Share Posted July 28, 2005 Prespex expands and contracts at different ratio's than glass so even if you could get something to stick to it it won't last. I agree with Alan, go the off cut bin. I get free prespex but can't find any use for it. Quote Link to comment Share on other sites More sharing options...
Dodgy Guy Posted July 29, 2005 Report Share Posted July 29, 2005 our entire 260L tank is perspex. and you dont need to use silion as they glue that is used is water tight as is. how ever 8mm is pretty thin. the first tank we made was 15mm and warped we now have a 20mm tank and its sweet as. ill see if i can find out what glue we used last time! Quote Link to comment Share on other sites More sharing options...
Alan Posted July 29, 2005 Report Share Posted July 29, 2005 The glue you use for perspex, actaully melts it and "welds" it together. That glue doesn't stick on glass. Alan 104 Quote Link to comment Share on other sites More sharing options...
Dodgy Guy Posted July 29, 2005 Report Share Posted July 29, 2005 loc tight 104 - my girl friends dad is an acylic molder. the reckons itll do the trick fine. alternatively buy a new tank? LOL Quote Link to comment Share on other sites More sharing options...
Warren Posted July 29, 2005 Report Share Posted July 29, 2005 I'd go with glass too. Unless you glue the perspex in at exactly the same temperature the tank will run at and then always keep it at that temperature, there will be stress setup in the join due to different rates of thermal expansion... Of course the stress will be small due to only small changes in T but it's there all the same. Why use a different material when you can use glass and overcome all the issues with a glue sticking and staying stuck long-term... I had a similar issue when building my 3m tank. It was a steel frame with glass set into it with silicone. I had to make the silicone 6mm thick between the steel and glass so it could stretch enough with the different expansion rates and not add any more stress to the join. The steel also had firbreglass over it so I had to use primer as well. Quote Link to comment Share on other sites More sharing options...
Pegasus Posted July 29, 2005 Report Share Posted July 29, 2005 loc tight 104 - my girl friends dad is an acylic molder For the cost of a few mils of Loctite 104 you could possible buy a new sheet of glass to replace the one in question. Loctite is fine... in a "no gap" situation, (Laser cut edges etc).. and would possibly work, although I would question its ability to withstand constant submersion for extended periods. Why take the risk for a few bucks. Many of us have "been there done that".. so the answers are here... less the pitfalls Bill. Quote Link to comment Share on other sites More sharing options...
Interfecus Posted July 29, 2005 Report Share Posted July 29, 2005 I don't know anything about glass working, but perhaps the experts could advise on this idea. Would it be a good idea for people in cases like this to score a couple of rings around the original hole before bonding a new sheet over the whole lot? The idea would be for the rings to terminate any cracks spreading out from the original hole. If it would be effective, would a regular circle, opposing ovals, or a 'crinkled' circle be best? I don't need this now but just had the idea and was wondering how effective it would be. I don't have any spare glass around to test it either. Quote Link to comment Share on other sites More sharing options...
Alan Posted July 30, 2005 Report Share Posted July 30, 2005 Are you talking about a thru hole, like one for a window slide button??. Scoring only creates weaknesses for more cracks to run from. Sometimes it pays, in fact all times, to continue the crack to it's full length. Or solve the problem with a hammer. Alan 104 Quote Link to comment Share on other sites More sharing options...
Warren Posted July 30, 2005 Report Share Posted July 30, 2005 Are you talking about a thru hole, like one for a window slide button??. Scoring only creates weaknesses for more cracks to run from. Sometimes it pays, in fact all times, to continue the crack to it's full length. Or solve the problem with a hammer. Alan 104 Quote Link to comment Share on other sites More sharing options...
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