Construction techniques for acrylic aquariums? Rabbets / Lock Joints?

Oughtsix

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When I am constructing a woodworking project I frequently like to make use of rabbets (a dado on the edge of a board) for a bit of extra strength but mainly to make alignment when assembling much easier. I have a lot of woodworking experience but little acrylic construction experience. What do you acrylic experts think of this approach?


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This would be quite easy to accomplish with a router. Like my picture shows I would make the rabbet a little wider than the thickness of the sheet sitting in the rabbet so I would have a bit of a protrusion to smooth out with a flush trim bit. Maybe 1/32".

I would like to hear opinions???

I have also considered doing a simple lock joint but I am thinking this would be over kill.... or would it? It would certainly make alignment a breeze during assembly! I would most likely use a lock joint for the sides to the bottom and just use a simple rabbet for where the sides intersect the other sides. This profile would also be pretty easy to setup on a router, but would take a lot more care while doing the routing. A rabbet can be easily fixed if you have a jitter in your hand while cutting it. A lock joint would be much less forgiving.


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If I used rabbets or lock joints for constructing an acrylic aquarium what do you think it would do to the cementing process? I think I would use the stick pin method of inducing a gap to fill with the Weldon, then let the Weldon sit for a minute to soften the acrylic before pulling the pins and clamping. It seems like a lock joint would be harder to get a clear bond without air bubbles... but since I would only use the lock joints from the sides to the bottom I wouldn't be as worried about a visually distracting air bubble.

Thoughts?
 

BichirKing

Dovii
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my thought is this is way over kill so I like it! I was thinking of doing the rabbet or a dado then trim off the excess with a router on my next tank build. mostly to square it up since the pieces are not square to start with.
 

Oughtsix

Dovii
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my thought is this is way over kill so I like it! I was thinking of doing the rabbet or a dado then trim off the excess with a router on my next tank build. mostly to square it up since the pieces are not square to start with.
Thank you, I didn't think it was completely crazy! And who says there is anything wrong with overkill? :)

Just curious, what part of the acrylic is not square?
 
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BichirKing

Dovii
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Just curious, what part of the acrylic is not square?
so I got a free homemade 240g tank. po sealed it with silicone, tons and tons of it. I cut it apart using a router and a fence. when I put my square on the corners they're definitely not square. I was thinking about using a dado to seat the edges into with the Weldon40 in the dado. then use the router to trim off the excess. hopefully that makes sense.
 
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BIG-G

Goliath Tigerfish
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Because bonding acrylic is technically a welding process the strength all comes from how well the two pieces are bonded together instead of the shape of the acrylic.
The rabbit joint may work out okay, you could still get to the surfaces to make a proper bond. The lock joint just seem unnecessarily complicated and if it isn’t bonded properly will not add much strength.
 
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Oughtsix

Dovii
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so I got a free homemade 240g tank. po sealed it with silicone, tons and tons of it. I cut it apart using a router and a fence. when I put my square on the corners they're definitely not square. I was thinking about using a dado to seat the edges into with the Weldon40 in the dado. then use the router to trim off the excess. hopefully that makes sense.
Do you usually use a router for cutting acrylic... or was that just the easiest way to take apart the existing 240g tank?

The reason I ask is because I have a good cabinet style table saw but I have been really considering investing in a track saw for cutting 4' x 8' acrylic sheets. The track saw would also serve double duty for breaking down 4' x 8' sheets of plywood and other wood working projects. It just seems like a track saw with a proper non-ferrous metal / plastic cutting blade would be the best way to get really accurate straight cuts. I have pushed many pieces of sheet goods through my table saw but I inevitably skew the sheet a touch when doing so leaving a slightly imperfect cut.

I have noticed that most track saws have variable blade speeds. It seems like a slower blade speed would reduce the possibility of melting the acrylic while cutting it? My larger table saw takes a 12" blade and is 3 phase which I use a VFD (Variable frequency drive) to run it off my single phase house current. The VFD gives me the ability to change the blade speed to pretty much anything I want. Would a slower blade speed do a better job cutting 1/2" acrylic?
 
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Oughtsix

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Because bonding acrylic is technically a welding process the strength all comes from how well the two pieces are bonded together instead of the shape of the acrylic.
The rabbit joint may work out okay, you could still get to the surfaces to make a proper bond. The lock joint just seem unnecessarily complicated and if it isn’t bonded properly will not add much strength.
In woodworking glue joint surface area makes a big difference in the joint strength. But I agree with you, since the acrylic joint is essentially melted then welded together the surface area of the joint should not be as critical as it is when joining two pieces of wood.

Thanks for the input! :)
 

BichirKing

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I have used a table saw with a fine tooth blade and it cuts well. I used the router because I didn't want to try and use my skillsaw and fence. our semi local plastics shop uses a router for all of its cuts. the very long cuts they use a panel saw type frame but it has a router on it. the router leaves a perfect edge for gluing, saw blades not so much.

oh and as far as speed goes im sure theres a magic spot between melting and the fastest cut speed, I don't know what rpm it would be.
 
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Oughtsix

Dovii
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I have used a table saw with a fine tooth blade and it cuts well. I used the router because I didn't want to try and use my skillsaw and fence. our semi local plastics shop uses a router for all of its cuts. the very long cuts they use a panel saw type frame but it has a router on it. the router leaves a perfect edge for gluing, saw blades not so much.

Very interesting. A router does leave a very nice edge... I guess I didn't expect a router even on a panel saw type guide to be the main cutting platform in a fab shop. I guess most CNC work on acrylic is essentially done on what is basically a fancy router.

I will keep this in mind as I am planning my build, thanks.
 
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