AI have a cake next week and can not find a styrofoam for a cake dummy! I need a 6 in. Can I use the cardboard and stack them up? If I can, what do I put around it to make it smooth before I buttercream and fondant?

Global Sugar Art has 6".  Also Dallas foam.  There are many sites.  You can google cake dummies and you'd be surprised how many there are.

AThank you! I don't have any time for something to get shipped to me, but I'll have to do that for the future! I'll YouTube as well!

I used those boxes with the lids that you get at the craft store (the craft paper brown ones that people paint and collage on).  I just ditched the lids and flipped them over.  They come in round, square, heart, etc.

I put a thin layer of piping gel on them.  I normally use crisco on my styro dummies but I was worried that the oil would weaken the box material.

See the dummies below...all boxes.

thanks you! 

funny thing is, if someone asked me to do those in real cake, i would freak worrying if I could get in all done in time!

not to mention the one with the quatrefoils on it is quite skinny and i would be so worried about it falling over!

i would probably suggest that i do something like this in fake cake where needed and do the rest in real cake.
 

AThose are gorgeous! That must have taken a lot if time! Thanks for the advice on the boxes!! Never would have thought of that

I've used stacked card board that I glued each piece together with craft tacky glue. Then I wrapped the project in foil to make the edges look nicer. You could glue ribbon to the sides of the foil for a more finished look. You don't have to wait for the glue to dry before you wrap it in tin foil. You can use it for the cake with in 24 hours.