Questions on bracing a plywood build with glass, and more...

[wannadivesteve]

Apparently with epoxy products take silicon adhesives pretty well and people are using them to adhere the glass panels on the front to the inside of the tank. Is the bond between glass and epoxied plywood as strong as glass to glass using caulk? Could you use glass cross bars and caulk them in on a plywood tank just as in an all glass constructed tank? I'm trying to figure out the best way to get my front panel in then add cross bracing after the fact.

For that matter, I'm likely going to have to build a tank on the spot considering the size I'm looking at, won't really make it through the door.... could a person in theory epoxy all panels ahead of time then move them in and caulk, or screw and caulk, the pieces together, as you would in a glass build, rather than building a single plywood structure then epoxying it?

Just curious. Thanks

 

[Lepisosteus]

you need to make one plywood structure before the epoxy. I don't believe people are using epoxy to attach the glass and the plywood, they still use silicone. Silicone does not stick well to wood but it does stick to epoxy. Use a wood frame, not glass

 

[wannadivesteve]

Perhaps I did not make myself clear. I was asking if attaching glass to epoxy covered plywood with caulk is as strong as attaching glass to glass with caulk, not attaching glass to wood using epoxy.

 

[wednesday13]

Perhaps I did not make myself clear. I was asking if attaching glass to epoxy covered plywood with caulk is as strong as attaching glass to glass with caulk, not attaching glass to wood using epoxy.

no its not as strong as silicone to glass... but plywood build windows are based on a different principle. the silicone becomes more of a gasket than a structural component as in an all glass build. The water pressure helps to make the seal with ur silicone gasket. The silicone will stick to the epoxy more than enough 2 get the job done. I build tanks lined with epdm liner and acrylic windows.. silicone does not adhere well to either material and my windows hold just fine due to water pressure. If you are worried of a good initial "stick" look into higer grade silicones like RTV, scs, dow corning, 3m5200.... as for the idea of using glass top bracing... no lol... u want any structural bracing done in wood then covered in fiberglass/epoxy like the interior of the tank or any area u want 2 keep from rotting out.

 

[Lepisosteus]

Perhaps I did not make myself clear. I was asking if attaching glass to epoxy covered plywood with caulk is as strong as attaching glass to glass with caulk, not attaching glass to wood using epoxy.

sorry then exactly what Wednesday said. With plywood builds the water pushing out on the glass creates a seal. The strength comes from the wood frame. Best of luck keep us updated

 

[wannadivesteve]

The original question was not about the glass front, it's about bracing. I'm fully aware about the gasket effect, I've heard of builds that used just a rubber strip and no bonding agent. I'm intending to use acrylic and a polyurethane based caulk for the front window.

I know all plywood surfaces must be epoxied to deter rot. Wednesday13 did answer the question on strength being less on a epoxy to caulk bond.

Specifically why I was asking, I wanted easy access to the tank window while bonding in the front acrylic, with the possibility of using glass top braces added after everything is in place rather than using wooden top braces. I've built both glass and acrylic tanks before, plywood is something I haven't worked with yet. I would prefer glass top braces, if there were no bonding strength issues, due to the fact light could pass through and I could use 12-15 inch wide braces rather than 3-4 inch wide wood bracing.

I still am wondering if there is a good way of bracing after the window is in place, using either glass or wood, so I have easier manipulation of an 8 foot span of acrylic and less risk of a sloppy job putting it in place. That's why I asked about caulking a fully epoxy sealed piece of wood in place after the fact rather than building it in prior to inserting the window.

Obviously if the strength of an epoxy to caulk to epoxy or glass bond is nowhere near as strong as a glass to caulk to glass bond then it would be a risk to bond after the fact using caulk. If the strength of that type of bond is the same or quite close that's another matter.

Are people successfully adding bracing after window placement on occasion, and if so, how? There's an easily found website about a plywood build in HawaII that implies he did, but with no specifics on how the joint bond was made, just a reference to it being time to add braces. It would be curious to hear how anyone is successfullying adding bracing AFTER windows are in place. I know epoxying the joint after the fact is a possibility, but that sounds kind of messy and I'm not sure what would happen if you got any of the epoxy on the acrylic.

I hope this clarifies my questions.

 

[wednesday13]

y so much worry of adding some braces on after the window install... simply screw or bolt them on? my 650 gal is made of steel angle iron...i just lag bolted my 2 top braces onto the frame after the window went in using 4 1/2"x3" stainless bolts. most all of the diy builds i see in wood use 2x4's or the hardwood ply used 2 make the rest of the tank for a couple braces on top. epoxy ur wood pieces before hand, pre drill the holes and slap em on. if ur worried past that u can silicone or epoxy over the joints/screws/bolts after there on.