I always wanted to make a three sided bowl. This one didn't go to well. About half way hollowing the inside it Decided to come apart. Probably my fault for not setting it up right with the grain.

 

oops

Looks like there could have been an internal weakness at the bottom where the tenon was created. The white streak in the center of the tan area may have been the weak area. Hard to say for sure.

I had that same thing happen with a spalted maple piece wasn't even a 3 sided bowl.  I'm wondering if there was too much tension on the tenon from the chuck with the RPMs that caused it to rip down the grain and split.  Had to think on that for a hot minute.  But that's probably what caused it.  But that is just a random wild guess as well.

34 minutes ago, lew said:

Looks like there could have been an internal weakness at the bottom where the tenon was created. The white streak in the center of the tan area may have been the weak area. Hard to say for sure.

Have to agree with Dan, that was my first thought too.

Looks like a catch in the second pic. At the top point. But the tenon may have been weak with the spalted area.

Looks like you had it set up okay.  The wood looks weak at the break.  Spalted?

There were no catches. Good to know about the white part being a weak spot. I will have to remember that.