I've been asked to do a two tier 12" and 8" round wedding cake it's a six layer rainbow cakes I always dowel and place cake cards in such a high cake but the bride does not want cake cards in the top tier as she wants to cut this on the day and wants the full effect of the rainbow the cake will be filled and covered in white ganache  then sugar paste but I am worried that the height of the cake could possibly sink or settle with out the support of the cake cards I will dowel the top tier but will this be enough to support such a tall cake it will not far of being 8" tall any advice would be great xx

i'm a little confused -- by cake cards do you mean cards or cardboards that the tier sit on? the bride cannot decide that for you -- you have to have the top tier on it's own board -- and i've never doweled a top tier -- i've put dowel under it to hold it up -- is that what you mean? you risk the cake caving in if it's not supported properly but i'm not sure what you mean by a cake card -- but i do agree that you risk failure listening to her

I've done a 6 layer rainbow cake that was only about 5 1/2- 6" tall.  Just don't make your layers so thick.  You will need to have have a good support system between tiers as that will be a heavy cake.  Also, make sure you use a sturdy filling.   If she wants to go with an really tall tier like 8", you really need the board for stability.  She can't have both....

@-K8memphis  I think she means the cardboard like in the middle of double barrel.  The bride wants to cut down through the whole tier to see the whole rainbow.

i see but i'm still confused because jay-jay40 says the cake will be 8" tall so that means one tier is 8" tall so with both tiers it's 16" tall then yes?

then i'm with jinkies and make thin layers so each serving will have the whole rainbow --

yoiks i didn't just agree with the bride did i?

Sorry for the confusion each cake will be 8" tall there will be a cake board underneath the top tier to support it on the bottom tier but also I will be stacking filling three layers of the rainbow cake putting dowels in then place a cake card on top then stack fill the other three rainbow cakes dowels in then ganache then sugarpaste but normally I would do this for both cakes to give the stability as they will be around 8" tall at 1" each layer without the filling I'm just worried if the top tier will not be as stable without the extra support in place if that's any more help xx

ok i got it -- so yes do like jinkies said and cut thin layers so that each serving will have the whole rainbow -- 8" tall is too tall to be without support -- 

when i make a cake like this i call it a 4 tier cake -- 

is she paying for all the servings?

I just made a cake with these sizes. My top was 8"x8" I had no problem with sinking or settling or sliding. I had s boats at the bottom and four dowels underneath it. No dowels or boards throughout the top tier. It sat out at room temp for 4-5 hours and was fine.

you were lucky

sure obviously it's possible but it's taking an unnecessary risk -- did you serve the cake where you made it or was it delivered by car somewhere and survived the ride as well -- if yes you're very lucky -- more power to you 

I've done a rainbow cake that was 7" high - each of the 6 layers were 1" thick with thin SMBC between; the cake was a 9" slightly carved round. Didn't have any issues at all - but the whole thing was also covered in ganache and then fondant.

Why would it slide? Unless you had an unstable filling or sat it in the sun it should be fine. I've done a few of these and never had a problem. There's a board underneath it and supports on the bottom cake to keep it from sinking. But it's only 8" high. Just make sure your butter cream is a good consistency and if your fillings are not buttercream just make a buttercream dam. Just have it refrigerated and transport it cold. It's only a two tier. 

sorry the particulars of this thread have been hard to pin down for me but if i made a sixteen inch tall cake that would be served as 4 tiers -- each serving would be a full rainbow and three of the tiers would be dowelled -- if i made one rainbow cake of my usual tier cake recipes i would be nervous to let it get much past six inches without help of some kind some skewers or carving off some of the edges -- yes 6 inches is about as tall as i'm comfortable going -- six inches finished product --

This is what I understood. She's making a two tier cake the bottom will be 12" and the top 8" . The top will be a rainbow cake so 7 layers. I believe she wants to put some cardboard in the top tier so maybe do four of the rainbow colors cardboard and then the remaining 3 colors. The bride doesn't want that she wants to cut down all of it and have the rainbow. So her question was if that is possible. 

Yes, she is talking about stacking an 8" double barrel on top of a 12" double barrel. That is essentially 4 cakes stacked.  You would not stack a 4 tier cake with supports in only 2 of the tiers.

K8 and I are advising her to tell the client that it needs supports or just tort her layers thinner so the cakes are closer to 6".  

Will it collapse if she doesn't?  Maybe not.  But, we are trying to tell her the correct way to do it.

Sorry there is some confusion it will be a 12" round and 8" high then the second tier is 8" and 8" high I will be doing six layers of colour in each cake  in the 12" round I will be layering thre e colours then dowel and cake card then layering the next three colours dowel then ganache then cover in sugar paste put a cake board under the 8" then I would normally  do the same for the 8" cake but the bride wants to cut this on the day and does not want any internal support as she wants the full effect of the rainbow colour im just concerned that a cake that tall with six thin layers will support its self and not settle etc hope this helps 

If your cake is of a sturdy type recipe, you can probably get by with the height on each tier of 8 inches without a cardboard somewhere in the middle of the tier.....but.....

Has the bride considered how difficult it will be to serve a slice of cake that is 8 inches tall?  That's won't fit on ordinary cake plates, and slicing and serving piece of that cake will be hard with the layers bending over and breaking while attempting to move the slice onto some kind of plate....plus that's a lot of cake or one serving.

For every 4"-6" of cake you need supports.  The support system is a super important part of the cake since that is what keeps the cake from falling apart.  So if you are doing an 8" high cake it has to have support in the first 4" of cake.  You need to let the customer know that you are the professional and know what can and can't be done and wont do something that could damage the integrity of the cake.

That being said, I have done rainbow cakes and ombre cakes quite often and they are usually about 5-6" high.  I would not do one that is that high, just doesn't make sense to me.  That high of a cake makes it so much harder to work with.  Also, I am with the bride, if I am ordering a rainbow cake I would want the full effect when I cut into it.