Tips on safely creating cantilever arches ?

[tenurepro]

Greetings all,
Any tips on how to safely create cantilever arches ? I want to create this effect, while still having the whole structure be solid for mounting and fragging corals down the road?

thanks!

 

[Fish Think Pink]

Greetings all,
Any tips on how to safely create cantilever arches ? I want to create this effect, while still having the whole structure be solid for mounting and fragging corals down the road?

thanks!

Hello, we used acrylic rods to peg the overhangs together for stability as freestanding using just mortar seemed risky. Our center arch with cantilever sides (think letter W) turned out well. We also used lace rock on the sides of W as its a lot more porous which translates to (relatively) lighter.

We measured out space, built and cured it in our garage, then put in tank. If you look at the pictures in my build thread, our W formation is essentially '2nd level' on top of a larger cave structure we built for tang sleeping (and princess anthias hiding out). This also meant if a "wing" were to breakoff, drop likely to kill anything underneath (ordered acrylic rods different sizes, drilled rock, mortared pegs in place. Our W is not designed to be disassembled, but our other stacked rocks are also drilled and pegged (and in some cases reef mortar shaped to make bottoms more flat/sturdy). We don't have a lot of fish, so no one yet has claimed the W top cave as a sleeping cave, but everyone loves to swim thru (and I have a sun coral sitting inside there since they don't need light).

 

[1ocean]

I been using a hammer drill and a concrete grinder to modify the rocks I bought so that they fit snug and do not require any glue or rods. Yes I bought a rod to use but ended up not needing it...
I will post pictures on my build thread once the lights come on to show you. I am still building this 300. At this point I have to finish the cabinets and all the wiring. And also hook up the GHL stuff. But fish are in now.
Corals are still in QT. Just hit 80 days with no fish in with them...

 

[RedoubtReef]

acrylic rods as suggested with some type of mortar works well.

 

[Sleepingtiger]

I found cya and using aragonite sand to be the best. Glues hard in seconds. The joint comes out stronger than the rock itself.

Using acrylic rods is very hard because you have to drill the angle perfectly if you want the rock to come together the way you pictured it. Easy if you have flat base and drilling into a soft material like wood. But this is rock and the rock has an irregular shape.