SOOO let's help make this a better cake making world by sharing just what I went through to make this cake;-)! Of course you might make yours different but here's what worked for me:).
This tutorial is broken down into different "phases": the neck, assumptions, the board, the template, and the cake.
First off here is a quick YouTube video with a brief description of our guitar cake:
Next here are more or less my 'steps':
Make the Neck
Since the neck needs to be very firm it should be done at least a week or two ahead of time. I made rice krispy treats using the same formula used here. I modeled it and utilized the flat table top to get a flat surface on one side and rounded the top by hand. Do your best with the headstock and if neccessary you can trim off areas when fully dried. After drying for a few days I covered it with a thin layer of gumpaste. Also, I made the guitar bridge with gumpaste since it needs to support some tension. After drying the neck for another day or so I then covered it with marshmallow fondant. Now that the neck is done time for the board but first..
Just like we have assumptions in engineering problems, I had to make some assumptions about this cake. I assumed I would use real guitar strings. Because really there is no other way of getting the effect of a really cool guitar cake using buttercream or dental floss!
THEREFORE the supporting structure had to be built in a way to support the string tension (even if it is minor). Which means I needed to somehow secure the strings to a support member that attached to the board itself. So now..
So it really helps to have the actual guitar you want to make especially if you want it to be life size. Trace the perimeter on a large piece of cardstock and cut out your template. Here is where I cut a slot for the support section necessary to hold the strings. Next..
Make Your Board
I purchase a 2' by 4' board at home depot and had it trimmed down so that it was somewhat larger than the cake itself. Also, I asked them to trim the scraps down to a size width similar to that of the string housing with a height that would clear the cake and elevate the strings just above it.
Before putting on the string housing structure I noticed the rice krispy treat neck really needed support. Even though it is firm there is no way it was going to stay elevated on its own. Soo... now what!? I built a supporting member out of strips of cardboard (using sheet cake boards). Next I covered the wood board and the cardboard support in cabinet wood print liner.
Now that the board is almost ready and covered take your string housing piece, position well (using your template), drill, and connect. Now for the cake!..
Believe it or not the cake itself is the last thing to worry about here;). This cake is ALL about the prep work of the board! ALSO make sure to make a cake board out of a half sheet board for the bottom of the cake using your template. And now that that is done on to the cake!
I baked a half sheet and a quarter sheet cake to meet the dimensions of my template. Let cool completely and then freeze (this way it turns out moist.. if you freeze before letting it cool it will dry out so make sure to cool completely!). Freeze for at least 24 hours. Carving turns out just *beautiful* if you freeze. If you don't expect a much softer, difficult to decorate, and not so clean look:-/.
Now it's time to work FAST! When you are TOTALLY ready bring out your cake, carve the half sheet portion using your template (don't forget the slot for the housing!), move it to the shaped cake board, position the top portion using the template, and move it over as well. Next fill your cake. At this point the cake will be much softer. Refreeze for no more than a few hours or so. Then crumbcoat in buttercream (again don't forget the slot!) AND add the guitar curvature by building up the buttercream down the middle center.
And now finally! After a few hours for the buttercream to firm at room temperature paint some water and next cut and cover with tan colored template version of marshmallow fondant. After the fondant has firmed for at least a few hours I sprayed it with metallic gold Americolor airbursh color. After that, It was detail after detail from the actual guitar.
Good luck with your guitar cake project!!