My first red oak board bow also snapped in the mid limb when I first went to shoot it.
For me, it was that it had a hinge on it due to sloppy tillering, and all the force went right to that spot.
I do have to say, when you get ready to start tillering, put some pics up. You'll get lots of great feedback from a whole bunch of eyes. My next bow will be tillered that way.
You can also use imgur to host pics, it's free, and you don't even need to set up an account. it's at imgur.com
best of luck!