Hello everyone,
I am planning on making my son's 3rd birthday cake using the racing car pan star piped with buttercream. However, I would like to place it on top of a half sheet cake frosted with Pastry Pride. Do I pipe the car cake first then place it on the sheet cake or do I do all of it at once? Also, do I need dowels to support the car on the sheet cake? Your helps is greatly appreciated. p.s. I am working on uploading some of my newbie cakes.

Someone else may have a better way but I think I would put the cake on a board, decorate most of it and then place it on the larger cake (with dowels and powdered sugar in the area so the icing doesn't stick to the upper board) and then finish the bottom of the race car with the stars. For me there would be less time to get my arm stuck in the icing on the big cake while finishing the car!

Yes, you need to dowel it. Frost each cake seperately, dowel and stack.

Sounds like a cute cake!

I always place my character cakes on a separate cake board cut to fit and then decorate completely except for the border. I use dowel rods for support(usually the plastic white ones). After stacking the cake...I pipe a border around any of the cakeboard that is showing. Hope that helps!

I agree with piping then stacking with dowels. It is better to be safe than sorry.

Make sure you cover the board with something like foil or wax paper to keep it from getting soft.

now, do I need to cut the car's cake board to the exact shape of the car or is that jus really up to my taste? sorry for these dumb questions..

Unless you plan to serve both cakes separately, you really do not need to dowel or board them separately, just thought I would add that. Likely you want to serve them separately but a sheet cake can handle a character cake's weight without being boarded or dowelled, it is really for serving purposes that we do this.
You want your cake board for your car cake to be cut close to the size of the car so that when you put a border around the base of your car cake it will hide the board. So shaping it is the best bet.
Because you are using Pastry Pride, you might also want to put a sheet of parchment on the bottom of the board that your car cake will be on because Pastry Pride doesn't really crust and the board will likely stick somewhat to it. Because parchment is silicone treated, it helps stop the sticking issue. Most of the time we use a sprinkling of icing sugar in the area of where the upper tier will sit to help prevent sticking also but with the Pastry Pride, I don't think it will help much. Another option is shaved chocolate or coconut so that the upper tier is actually resting on that and not on the Pastry Pride covered cake.
If the cake will not be moved, you could also cut your dowels a bit higher than the height of the bottom cake's icing so that the cake rests on dowels and not on the cake but this will make it a bit less stable.
Hugs Squirrelly

Sorry, just wanted to add, I cannot get Pastry Pride here but my understanding is that it is a non crusting type of frosting sort of like whipped cream or Cool Whip would be so this is why there is more likelihood of having sticking issues with the board.
Hugs Squirrelly