What about corbels?

I was wondering the same thing myself. My overhang on the widest part of the curve will be 12", and I was concerned about the look - not having any supports, columns, etc.

Then I searched up islands on houzz.com and found that about 50% of the island overhangs had some sort of visual or actual support.

What does your granite guy say?

Can I ask what the overhang will be on the working sides of your counters? I'm looking to minimize mine, and I'm not sure if 1/2" overhang will be ok or not.

We have 15" overhangs and hubby didn't want corbels so we installed Counter Balance Supports after doing a lot of research. They have worked great! The link below is our post and photos of the support installation.

NOT the greatest photo but you can see our island here:

And our finished kitchen decorated for Halloween :)

Here is a link that might be useful: Support for granite - no corbels

For an 18" overhang you really should have a support. Corbels will do, although our granite guys called them "knee knockers," as will a leg of some sort. We used these flat iron supports for our 14" overhang. If you hunt around on old threads, you'll see several suggestions with photos.

18" is LOT of overhang. a lot of weight. It would be best to create a table like structure here with and apron and legs. If you choose to do some type of steel tubing (NOT flat stock!) support, it needs to be anchored into a pony wall that is well anchored into your subfloor rather than cabinets. Cabinets won't be heavy enough to counterbalance 18" of heavy stone.