Plywood Tank Variation, Ballsy or foolhardy?

[cvermeulen]

I'll be waiting.....

Oh don't worry. I can't wait to share photos of this uber ghetto fab test. I have a broken pane from a 135 in my shop I'll glue the test piece to, put a couple 3-4 olympic 20kilo plates on and then use my engine hoist to lift it up a couple inches and let it hang for a few days.

 

[basslover34]

I like the thinking ... I've actually thought of it before as well.. but I really didn't like the look after mocking it up... I like the glass on the inside because it hides the silicone and makes for a cleaner look when you "dress up" the frame around the glass... JMO ofcourse.

Looking forward to seeing the test none the less as I'm sure that there is a use for this that I haven't fully thought out...

 

[D-007]

What ever happened to the test and possible results?

 

[Pharaoh]

I would be interested to see the results as well. Also, I had forgotten about this thread, which made me think of it all over again. My only two concerns would be, glue/silicone (which has been covered) and the strength of the sides. Since the sides are made of plywood, you would have to be absolutly sure that the side would not bow. This might put undue stress on the adhesive causing it to fail. Just some thoughts although I like the idea.

 

[RBE17]

It doesn't appeal to my conservative nature, but if the numbers support it, go for it. The psi rating you quoted, is that tensile or shear?

 

[cvermeulen]

The test I constructed is sitting in my frosty garage, waiting for me to grow some motivation and pile weights on it. Sorry, I dropped the ball on this project - huge economic cutbacks and whatnot have me trying not to do anything in the garage to save money. I've got three weeks off as of Friday, so I'll be out there puttering around, possibly making myself an updated algae scrubber for my 120 and building whatever other contract projects I can!

Edit: so hopefully I'll get this test started. I need to 'borrow' a 100lb steel plate from work to lay on the glass and lift. 100psi hanging for a week should be enough to inspire some confidence. After that I'll keep adding weight till it breaks.

 

[cvermeulen]

I would be interested to see the results as well. Also, I had forgotten about this thread, which made me think of it all over again. My only two concerns would be, glue/silicone (which has been covered) and the strength of the sides. Since the sides are made of plywood, you would have to be absolutly sure that the side would not bow. This might put undue stress on the adhesive causing it to fail. Just some thoughts although I like the idea.

That's a good thought. I had considered using a steel frame in the front of the structure in the beginning, mostly to cut down on the size of the bracing required. I'll have to run a seperate test to see how fiberglass adheres to steel though. In my experience so far a braced plywood tank doesn't bow significantly, so as long as it's designed properly, I wouldn't expect too many issues.

 

[cvermeulen]

It doesn't appeal to my conservative nature, but if the numbers support it, go for it. The psi rating you quoted, is that tensile or shear?

I think it's tensile. I haven't looked at the data sheet in a while. With 500% elongation though, the adhesive would just move along the shear plane until it was largely in tension anyway. One interesting thing I read was that when bonding to glass and fiberglass substrates, the failure mode of the glue was cohesive, rather than adhesive, meaning the silicone tore in the middle somewhere instead of pulling away from the substrate - that's good news as it means the material strength of the adhesive is a good indicator of what the joint strength between the two materials can be if properly done.

 

[RBE17]

I think it's tensile. I haven't looked at the data sheet in a while. With 500% elongation though, the adhesive would just move along the shear plane until it was largely in tension anyway. One interesting thing I read was that when bonding to glass and fiberglass substrates, the failure mode of the glue was cohesive, rather than adhesive, meaning the silicone tore in the middle somewhere instead of pulling away from the substrate - that's good news as it means the material strength of the adhesive is a good indicator of what the joint strength between the two materials can be if properly done.

Good deal. It sounds like you have your bases covered. I'd be interested in seeing how this pans out. It's too "risky" for me, but I don't even like relying on the water to hold the viewing windows in place on the plywood, home built aquariums.

 

[nolapete]

Think old school before all glass aquariums when every tank had a metal frame. Build a frame for the glass out of angle iron then bolt the frame to the fiberglass with whatever sealant in between. Set the glass in the frame with sealant and you're done.

My friend has two 22' x 4' x 3' plywood tanks in his house with pond liners in them. I'll ask him how he secures the glass.