AI need some help with the sides of my cake. Working with fondant, No matter how hard I try, I cannot seem to get my cake sides vertical, with nice sharp edges at the top. It almost seems like my icing under the fondant is sliding off, and pooling at the bottom, giving my sides a bulbous appearance. Any advice or tips? Is my fondant too thin? Icing too thick?
AAre you putting your cake on a drum? It's a good way to get straight sides with the buttercream.
I guess you are using a butter based buttercream under the fondant? I use the 'upside down frosting method' to get sharp corners and this is the link to a video tutorial that will show you how to do it: http://jessicakesblog.blogspot.se/2011/06/video-tutorial-upside-down-frosting.html. It's revolutionized how my cakes look :) The other thing you need to do is let the frosted cake sit in the fridge for sometime so that the buttercream hardens before putting on the fondant. This gives you a nice hard base to work with. I usually let my frosted cakes sit overnight in the fridge before I cover them with fondant. You do need to work fast though when covering with fondant because due to the warm temperature the buttercream will start to soften a little. Using ganache instead of buttercream resolves this problem, but I haven't done it myself. Have been happy with how my cakes have turned out so far :)
It's good if you do have a nice thick layer of frosting to begin with. And when you roll out your fondant it shouldn't be too thin otherwise you will end up with it tearing. I think the usual thickness is around 3 mm (milimeters). Hope this helps and good luck!
This is the method I use for frosting cakes, similar to the upside down method, but you don't have to flip the cake. I prefer ganache, for me it's easier to get sharper edges-not that it can't be done with a good BC. Just make sure you let it harden as stated above.
Also, are you letting your cakes settle between baking, torting, and covering? This can help avoid bulging. It's difficult to diagnose without a picture, do you have a picture you can post of the problems your having?