I want to make a cake carved from4 or 5 9 inch layers, do I need to dowel any of these layers, or can i just stack them up with nothing between them?
I would probably put one board in there after the third layer and make sure to central dowel with the spike driven into the base.
Anytime I carve I freeze all of my layers. I stack while frozen and carve. I then mark one side of my carved cake (usually just using a paring knife to cut down one side of the entire cake, just to line it back up again) Then I dis-assemble each layer, add filling or buttercream, and my rule of thumb is a cake board and dowels every 4" of cake. So if you are using 4 layers of cake (2" deep) then you would only need one cake board and then some dowels in the middle of the cake.
Anytime layers are stacked up there should be a cake board & some type of doweling every 4"5" of heigth.
You are wanting to stack 8"-12" high. It definately needs support! Also.......a 9" round cake 8" high will be very top-heavy and unstable for any transporting/moving around
I do usually put support boards every few layers but I have done cakes before that were 6-7 layers high with no boards, but using a large center dowel...I did my first big dino cake like this and it held up fine.