Acrylic to Plywood

[ScottF83]

I have some DIY plans formulating and currently in the stage of deciding whether to use glass or acrylic after receiving quotes for both.

I'll share the plans later of course and I think you'll love them!

But first... my question... how do you attach an acrylic 25mm sheet to a plywood aquarium?

I've trawled the internet and can't find a good answer. Lots of talk about using the wrong sealants and leaks occurring, which of course I want to avoid, but nothing definitive or clear or put in the form of a simple picture.

I'm okay with the glass option... just correct aquarium sealant and a wooden beam frame to sit the glass within.

Thanks all
Scott

 

[jsker]

Yes on the glass question. Plywood, I am still out on the whole plywood thank thing. If I were going to do play, I would gel coat the interior of the box and embed the acrylic in the gel coast and then seal it. Doing the way I suggested, you would be better off buy a tank.

If you did the bracing with hardwood on the glass, I bet that would look pretty cool

 

[CodyRVA]

I shared this video a few weeks ago, might not answer any questions, but could give you some ideas...

https://www.reef2reef.com/threads/diy-200-gallon-plywood-bottom-aquarium.244290/

 

[ScottF83]

I shared this video a few weeks ago, might not answer any questions, but could give you some ideas...

https://www.reef2reef.com/threads/diy-200-gallon-plywood-bottom-aquarium.244290/

Yeah that video initially follows the exact same ideas that I saw on the 'DIY Aquarist' youtube channel. Also bought his book which has a full section on the subject.

It does show that glass is easy to work with, just get it in position and seal it with normal aquarium sealant.

But unfortunately doesn't answer the acrylic question which, I believe from what I've read, doesn't seal very well with the sealants we'd use.

Yes on the glass question. Plywood, I am still out on the whole plywood thank thing. If I were going to do play, I would gel coat the interior of the box and embed the acrylic in the gel coast and then seal it. Doing the way I suggested, you would be better off buy a tank.

If you did the bracing with hardwood on the glass, I bet that would look pretty cool

You'll understand why I am using plywood when you see the design It will be fully coated and sealed so the idea of just making the sealant thick enough to cover over the acrylic is interesting. I'd still like to see a definitive answer in an article or via someone's plywood+acrylic-window build.

 

[ScottF83]

Still can't find the answer

 

[AlexG]

I am building a plywood tank but I am going to go with glass. Sealing acrylic to plywood is something I have not seen a how to on. You might be able to use a gasket type of seal if you can't find a sealer that can bond acrylic to the epoxy used to seal the plywood.

 

[ScottF83]

I am building a plywood tank but I am going to go with glass. Sealing acrylic to plywood is something I have not seen a how to on. You might be able to use a gasket type of seal if you can't find a sealer that can bond acrylic to the epoxy used to seal the plywood.

I found a very old article that seems to wrap the acrylic edges in a bonding epoxy... But I'm not sure how I'd match the products used!

Glass would be so much easier but it's also 2-3 times the price for what I need. (attached)

 

[AlexG]

How big is the tank? Where did u get a glass quote from?

 

[Lowell Lemon]

Acrylic and silicone do not mix very well. However many large aquariums use concrete with a metal channel and "wet" set the acrylic panel in silicone with another channel that clamps the parts together. So the silicone just acts as a resilent seal. The metal channels are epoxy coated before assembly. So you make a mechanical seal and depend on the silicone as a gasket. Good luck.

 

[ScottF83]

How big is the tank? Where did u get a glass quote from?

That's 7 foot wide, about 300 gallons

Quote from Aquariums Manufacturing Ltd just shy of £1k for the glass in appropriately thick Optiwhite glass

 

[ScottF83]

Acrylic and silicone do not mix very well. However many large aquariums use concrete with a metal channel and "wet" set the acrylic panel in silicone with another channel that clamps the parts together. So the silicone just acts as a resilent seal. The metal channels are epoxy coated before assembly. So you make a mechanical seal and depend on the silicone as a gasket. Good luck.

Yeah the guy on another forum who built a ridiculously sized acrylic tank (4000+ gallons I think) used a metal frame to mechanically frame and seal the water in

It does lead itself to some methods I found with even more Googling (done so much googling lately... SO MUCH).... both use an element of what you said. The first is epoxy painting the plywood, setting the acrylic in and using "Dow Corning 795 Silicone Building Sealant" as a gasket. It holds the acrylic in place, glues itself to the epoxy and the water pressure does the rest.

The other method is more mechanical in using stainless steel bolts through the acrylic with "3M 5200FC" marine sealant. A specialised product used as a sealant and adhesive above and below the waterline on boats. So you simply line the edge of the acrylic with this stuff, screw the bolts hand tight and the sealant acts as a marine safe gasket. My design has a double layer of 2x4 wood around the ply (as a brace) the bolt heads can be easily hidden. As I type, this method is starting to appeal to me the most! I can source the goods in the UK easily and it's an easy method to understand - especially if it leaks, there aren't many things involved!

http://solutions.3m.co.uk/wps/porta...pair/GeneralBoatRepairs/SealantAdhesiveGuide/

What do you guys think?

 

[AlexG]

I would also consult a public aquarium if they have tanks sealed with large viewing panels of acrylic as the same issue would exist if they have a concrete tank. Actually I would message the user Pigpen on this forum he has a 20,000 gallon reef in his home. I bet he would have some ideas for you.

 

[ScottF83]

I would also consult a public aquarium if they have tanks sealed with large viewing panels of acrylic as the same issue would exist if they have a concrete tank. Actually I would message the user Pigpen on this forum he has a 20,000 gallon reef in his home. I bet he would have some ideas for you.

TWENTY THOUSAND?!?!

That's quite a tank.

I will do, thank you! I've emailed 3M technical support for their input too.

Seen some talk online of a good seal being made between the epoxy resin used to waterproof the ply, a two part acrylic solvent and the acrylic sheet.

Think I'd still go the bolt and marine sealant route but then perhaps overcoat with epoxy resin in a layer that crosses from the tank ply over the edge of the acrylic and maybe an inch over the tank-side of the acrylic. Solvent too so the molecules all mix up.

Was thinking on the way home tonight that I could build either a quarantine tank or sump out using the same materials to test the water holding ability of the above theory!!

 

[AlexG]

I agree with testing the theory. I think that is a cool tank design for sure. I was originally going to make a drop off tank but with its size 2 giant tanks for one system worked out to be a better design for me. I have a build thread going if you want to see my progress and design. Please share the test setup I am interested is seeing how it works.

 

[Pigpen]

It is scary the amount of bad info people dish out . there is only one way to do it right . Do you have the tank built yet ? did you form a rebate to hold the panel ? silicone will not really stick to acrylic and we do not use a pressure seal so you have to rely on surface area of the seal being small and the pressure being low . any form of mechanical bond between the tank and acrylic will leak very fast as the two will move quite a bit when water is added .most of us who know how to do this dont tell people as the liability id pretty high and everyone is sue happy .

 

[ScottF83]

It is scary the amount of bad info people dish out . there is only one way to do it right . Do you have the tank built yet ? did you form a rebate to hold the panel ? silicone will not really stick to acrylic and we do not use a pressure seal so you have to rely on surface area of the seal being small and the pressure being low . any form of mechanical bond between the tank and acrylic will leak very fast as the two will move quite a bit when water is added .most of us who know how to do this dont tell people as the liability id pretty high and everyone is sue happy .

No the tank is not built. I have not even purchased a single screw yet! This is all planning at the moment.

So what is the right way to do this?

A rebate to hold the acrylic, ok. But what products to make the seal? What order to apply them? Just a load of silicone in the rebate? Is that because it doesn't hold so it's just a forced sandwiched area?

Feel free to pm me instead. I won't sue haha

 

[Pigpen]

I will save you a huge headache . just get an all acrylic tank . dont bother with a plywood tank . I have been there and done that and dont wish it upon anyone .

 

[AlexG]

I will save you a huge headache . just get an all acrylic tank . dont bother with a plywood tank . I have been there and done that and dont wish it upon anyone .

I am in the middle of building 2 plywood tanks lol. I am using glass for the fronts though.

 

[blitz49]

Take a look at this , but I still would not trust acrylic bonding to wood. Remember acrylic warps.

 

[Lowell Lemon]

I will save you a huge headache . just get an all acrylic tank . dont bother with a plywood tank . I have been there and done that and dont wish it upon anyone .

I agree 100% on the plywood tank concept. The cost of marine grade and proper epoxy and all the potential problems would leave me sleepless at night. What about the worms that can bore right into the wood with no problem...yikes.

Make sure the acrylic panels are of the required thickness to prevent flexing and make sure the rebate is completely rigid. That is why public aquariums use concrete with a metal rebate with a metal back plate bolted around the acrylic and wet set silicone for large panels. I personally would never use this technique and build the entire tank out of proper acrylic panels. I would not pretend to be able to pull off a million gallon aquarium like the Outer Bay Exhibit in California. Acrylic panels were 12 1/2" thick and butt seamed on site for that display. If you are observant you can see the seams due to light transmission. Impressive build.