I'm sorry you are having trouble with your angel food cakes. I am attaching a link to our angel food cake "how to" information.
One thing that is very important is to be sure that your bowl, beaters, spatulas and pan are all completely free of fat or oil, as this will prevent the egg whites from beating up properly.
Another tip is to be sure to add the sugar to the egg whites gradually, beating the mixture well after each addition, and beating to stiff and glossy at the end. When you fold in the flour mixture, you need to be very gentle, so that you do not break the foam that you have made by beating the sugar and egg whites.
Here is the link:
Answered 11/08/2012 by Marcia-BettyCrocker