What kind of glue did you use?

The Alpha 40 has an aluminum wing joiner tube, so if you just saw it in half, you will need to replace the tube.

You may be able to saw very carefully, around the aluminum tube, and get it back apart. Then clean up the joining surfaces and try again. When I joined mine, I used 30 minute epoxy, and just sat there and held it for 15-20 minutes until it was cured. It is pretty tough to clamp with the dihedral angle, but the joiner tube and wooden dowel keep it straight, you just need to hold it together.