bonding/gluing glass or acrylic to fiberglass

[Charney]

I am working on getting a few larger acrylic tanks. They will only have one viewing window and the rest will be fiberglass. I am pretty sure i will be running my fish room with air, including this larger tanks. I want to make chambers in the tank for Poret. How do I attach either glass or acrylic to do this? Thank you

 

[wednesday13]

I am working on getting a few larger acrylic tanks. They will only have one viewing window and the rest will be fiberglass. I am pretty sure i will be running my fish room with air, including this larger tanks. I want to make chambers in the tank for Poret. How do I attach either glass or acrylic to do this? Thank you

Silicone adheres very well to epoxy paints… pretty sure the same goes for gel coat. Those would be the 2 possible things ull b working with. Id def. go with glass over acrylic. There are some good silicone products these days that adhere a bit better to acrylic, but not nearly as well as they do to glass. Might have to scuff up the gel coat/epoxy for a bit better bite but not much. I think gel coat uses a wax finish. Id ask the mfg. of the fiberglass tanks how to prepare the surface for silicone depending on the coating. Even tho the tanks windows may be acrylic the silicone is more of just a gasket there so i wouldn’t copy that for trying to glue in strips to hold the poret.

 

[Charney]

Silicone adheres very well to epoxy paints… pretty sure the same goes for gel coat. Those would be the 2 possible things ull b working with. Id def. go with glass over acrylic. There are some good silicone products these days that adhere a bit better to acrylic, but not nearly as well as they do to glass. Might have to scuff up the gel coat/epoxy for a bit better bite but not much. I think gel coat uses a wax finish. Id ask the mfg. of the fiberglass tanks how to prepare the surface for silicone depending on the coating. Even tho the tanks windows may be acrylic the silicone is more of just a gasket there so i wouldn’t copy that for trying to glue in strips to hold the poret.

thank you. I will look into that
Just realized i can buy fiberglass sheets
Is it hard to bond the fiberglass sheet to the tub?

 

[wednesday13]

thank you. I will look into that
Just realized i can buy fiberglass sheets
Is it hard to bond the fiberglass sheet to the tub?

Honestly id probably still go with glass since silicone sticks to that best. Itd be a weaker bond with the fiberglass sheets.

 

[andyroo]

Hi Wednesday,
Interesting: "Silicone adheres very well to epoxy paints…" is pretty much the opposite of my experience & most/all I've read in building both aquaria & ancient Boston Whalers (boats). My experience is that silicone doesn't stick to anything but glass, and pretty much nothing sticks to it in return. Yes, it's fine~great as a sandwiched gasket. Charney might get away with if the epoxy is highly roughened, but I'd (strongly) recommend a polyurethane sealant/cement (like 5200) for sticking to epoxy. Though 5200's not great with glass, it's better than silicone-to-epoxy. Silicone to glass & held as gasket is good, can back/lock with glassed epoxy to hold that sandwich.
Appreciating your massive experience, I'm curious for FishDance's response in this, as his experience is/was similar to mine.
GelCoat tends to be a polyester resin, though cures differently so more-or-less waterproof. It's used as the wet later on boats as it's way cheaper than epoxy, so the headache of setting gets mitigated in the factory's economy of scale.

Charney,
just make sure you're not setting polyester resin (fiberglass) in direct contact with water as it will soak/degrade, though that's for resins & not necessarily for factory-produced FRP sheets. The wet-layer needs to be either polyvinyl or epoxy resin, the latter being the preference for smaller & home jobs. You can do the structure with a poly resin as it's relatively cheap, but it's also stinky & nasty & toxic so ventilate the room (vinyl's far worse). For the final & bonding corners etc, epoxy resin ticks to old poly, but poly resin won't stick to epoxy very well. It doesn't stick to cured poly terribly well either. Roughen & clean.

 

[Charney]

Hi Wednesday,
Interesting: "Silicone adheres very well to epoxy paints…" is pretty much the opposite of my experience & most/all I've read in building both aquaria & ancient Boston Whalers (boats). My experience is that silicone doesn't stick to anything but glass, and pretty much nothing sticks to it in return. Yes, it's fine~great as a sandwiched gasket. Charney might get away with if the epoxy is highly roughened, but I'd (strongly) recommend a polyurethane sealant/cement (like 5200) for sticking to epoxy. Though 5200's not great with glass, it's better than silicone-to-epoxy. Silicone to glass & held as gasket is good, can back/lock with glassed epoxy to hold that sandwich.
Appreciating your massive experience, I'm curious for FishDance's response in this, as his experience is/was similar to mine.
GelCoat tends to be a polyester resin, though cures differently so more-or-less waterproof. It's used as the wet later on boats as it's way cheaper than epoxy, so the headache of setting gets mitigated in the factory's economy of scale.

Charney,
just make sure you're not setting polyester resin (fiberglass) in direct contact with water as it will soak/degrade, though that's for resins & not necessarily for factory-produced FRP sheets. The wet-layer needs to be either polyvinyl or epoxy resin, the latter being the preference for smaller & home jobs. You can do the structure with a poly resin as it's relatively cheap, but it's also stinky & nasty & toxic so ventilate the room (vinyl's far worse). For the final & bonding corners etc, epoxy resin ticks to old poly, but poly resin won't stick to epoxy very well. It doesn't stick to cured poly terribly well either. Roughen & clean.

thank you for the reply. Ideally i want to build glass chambers. Your recommendation is that i look into 5200's to mount the glass to the tub?

 

[jjohnwm]

I've never experienced or really even heard about any problems with silicone on epoxy; I've made a bunch of plywood tanks sealed internally with various epoxies and always just glued the glass front in with silicone. In fact, a few of my earliest tanks back in the 1980's didn't even have any kind of wood support under the glass to support its weight; the glass was just laid down onto the silicone and left to cure, so that when the tank was placed upright the entire weight of the glass was held up by the silicone alone...no little "shelf" underneath it to help out. Most of those tanks were in service for at least ten years, and some much longer than that. I always used plain old GE pure silicone, what they now call Silicone I.

Research is important before trying anything...but the downside is that if you do enough of it, you will always be able to find an example of somebody warning you that what you want to do is destined to fail. Caveat aedificator...builder beware!

Acrylic? Acrylic??? Who the hell builds tanks out of plastic?

 

[wednesday13]

Hi Wednesday,
Interesting: "Silicone adheres very well to epoxy paints…" is pretty much the opposite of my experience & most/all I've read in building both aquaria & ancient Boston Whalers (boats). My experience is that silicone doesn't stick to anything but glass, and pretty much nothing sticks to it in return. Yes, it's fine~great as a sandwiched gasket. Charney might get away with if the epoxy is highly roughened, but I'd (strongly) recommend a polyurethane sealant/cement (like 5200) for sticking to epoxy. Though 5200's not great with glass, it's better than silicone-to-epoxy. Silicone to glass & held as gasket is good, can back/lock with glassed epoxy to hold that sandwich.
Appreciating your massive experience, I'm curious for FishDance's response in this, as his experience is/was similar to mine.
GelCoat tends to be a polyester resin, though cures differently so more-or-less waterproof. It's used as the wet later on boats as it's way cheaper than epoxy, so the headache of setting gets mitigated in the factory's economy of scale.

Charney,
just make sure you're not setting polyester resin (fiberglass) in direct contact with water as it will soak/degrade, though that's for resins & not necessarily for factory-produced FRP sheets. The wet-layer needs to be either polyvinyl or epoxy resin, the latter being the preference for smaller & home jobs. You can do the structure with a poly resin as it's relatively cheap, but it's also stinky & nasty & toxic so ventilate the room (vinyl's far worse). For the final & bonding corners etc, epoxy resin ticks to old poly, but poly resin won't stick to epoxy very well. It doesn't stick to cured poly terribly well either. Roughen & clean.

Agree with ya 100% that 3m5200 is superior to regular silicone for most mixed materials. Theres some new ones out these days also like ms300 and m1 construction adhesive. My favorite is gold label aquarium and pond sealer but its hard to get in the states. Its alot thicker bodied than 3m and stickier. Ive only worked with pond armor and max acr with silicone. In both cases the epoxy pulled up with the silicone when i tried to remove it.

I know gel coat is different tho and id wager thats what most factory made tanks are using for the price break like ur saying. Viktor used gold label with success on gel coat even underwater to repair a separated seam.

 

[esoxlucius]

The inside of my fibreglass tank is some kind of epoxy I guess. I've often wondered what the "shelf life" is of the contact strength between the epoxy and the viewing window, which of course is bonded by silicone. Glass to glass, great, no worries there, epoxy to glass on the other hand, I haven't got a clue!

I've had my tank 5 years now and the glass panel is just held with silicone alone. The glass doesn't rest on some kind of lip or ledge that John mentioned. And as far as I can see the panel is solid, it hasn't slipped, or leaked, not one drop in all that time. It's a little unnerving actually because that glass panel probably weighs quite a bit.

So currently I'm on the side of the fence that suggests that silicone and epoxy are good friends! I just hope their friendship remains solid!

 

[andyroo]

Lads/Lasses,
I stand corrected - good, as silicone-to-epoxy anxiety has been one of the things curtailing my next-big-build.
My experience might be suffering from the odd-brand silicone that we tend to get; I might do well to find another importer.