ok - I've been researching this at length, and have seen a number of methods - but I still have some questions and concerns. My application is slightly different than the examples i have seen so I want to be sure..

my 3D dinosaur has a head with open jaws made out of hardened RKT. I almost lost the top and bottom jaw because the weight of the RKT pulled the structure down around the pvc pipe. I managed to save it and laid it down to harden (rather than right side up) and it's been sitting for a good week so is hard and set. My concern is that I have read butter cream can soften RKT, so I REALLY dont want to risk softening it and having the structure fall apart. Royal icing seems to be the other option (or modeling chocolate) to be honest, this thing is so big and the head wont get eaten (neither will the tail or legs) and to waste that much chocolate makes me cringe. So I am back to the royal icing....

Ok so if i use royal icing, will that weigh a lot? how will I get the fondant to STICK to the royal icing once it dries. Is there anything other than Royal icing that sounds like it will work better?

THANK YOU!!!

How about a thin layer of clear pipping gel?

what is piping gel- would it harden and fill in gaps?
thank you!

I am NOT an expert on RKT by any means, but using royal icing is a pain. No matter what you do you will get little bits of icing sticking up all over the place when it's dry and you have to sand it down, else your fondant won't be smooth. If you do manage to get the whole thing smooth, spritzing with a fine spray of water should make your fondant stick.
Last time I resorted to ganache, on small things the cost maybe wouldn't be a problem, but on a big dinosaur it would be expensive (more so probably than modelling chocolate due to the cream in ganache!).
Hopefully someone else with have some good ideas.

I use candy melts over my RKT, everytime. I started this last summer when I was doing a Buzz Lightyear cake. http://s314.photobucket.com/albums/ll426/ShelbyLynnCakes/?action=view¤t=Buzz4.jpg#!oZZ55QQcurrentZZhttp%3A%2F%2Fs314.photobucket.com%2Falbums%2Fll426%2FShelbyLynnCakes%2F%3Faction%3Dview%26current%3DBuzz6.jpg We had a spaceship that was crashing into the cake and was coming in on an angle. Made the ship, cut the angle, just perfectly, covered it in bc, then fondant and went to put it on the cake. It literally fell apart in our hands. It was very hot and humid out and it just was not going to hold together. So, we figured that candy melts has a high melting point. We used the same exact batch of RKT, redid our ship, hardened it in the fridge (again), and than painted on the melted candy melts. Put it back in the fridge to harden, and when it came out, nothing was going to melt that or have it fall apart. We haven't made anything with RKT since that we didn't put on the candy melts. It has held it's shape perfectly every single time. Hopefully this would work for you.

the candy melts are tempting - though i do worry about the weight and cost. the head is about 14" long, roughly 10" high, and maybe 8" wide. this is just the head. the legs and tail would be double that I saw the space ship (great cake by the way) but I am guessing by visual size, that the head is probably 4 times that size, or more - so with tail and legs - maybe 12 times the amount of chocolate would be needed. I can't recall how much the chocolate melts are, but I'm buessing this could be 30 bucks or more in chocolate? does that sound right?

I've been tossing some ideas around - since it's not going to be eaten, flavor is not an issue. I thought abou flour paste - like the paste they use to make pinata's - would that work? or would the moisture soften the RKT to much. what about a fudge variation - cooked until not quite hard so its like sludge (LOL) just some thoughts. I'm trying to keep the cost down. homemade fudge or something like it might be cheaper than the melts - but then again, risking something unknown on a multi-week project only to end in in disaster is not what I want....

oy

AC Moore has the candy melts at $1.99 for a one pound bag. I just melt them, and use a paint brush to paint the melted candy onto the piece. I usually figure on giving it two separate coats. It fills it the gaps and makes it solid. The space ship probably used about 3 ounces, at the most. I can't recall anytime we've used them that there was any discernable difference in weight. On a piece as large as yours there would of course be some extra weight on the whole piece, but I think it would dry hard enought to support the whole thing.

I use almond bark or candy coating to cover my rkt.
Just smooth it on with your hands and let the excess drip off, it will fill in any gaps and help the rkt hold their shape.
I've done it on a 3-D Yoshi before with an open mouth and it worked fine.
I did the lower jaw as a separate piece though and attached it using skewers and melted bark as glue, held fine.

thank you everyone!! I am actually kicking myself daily for taking on a huge project like this without ever having done anything like it before. I have baked cakes occassionally over the years (as the average person has) - and last year took a huge leap buying an stand up bear pan and made an elmo out of it for my daughter. that was adventuresome THEN. then a couple months ago I tried my first batch of MMF and did a cake just to see if I could make it.

Now, I'm attempting a 3D- Armature - RKT covered - Fondant Covered - nearly 2 foot high - Cake. I AM CRAZY!!! Everything has been a crap shoot on this and I am so far into it i can't back out now. I have this vision it's all going to fall apart and be a mess a day before my daughters party - or the day of...

I can't thank you enough for your replies. I am thinking the candy is the way to go. What about, however, the thing I have been reading about chocolate siezing when exposed to water - if that is the case, how do you get the fondant to stick to the candy melts after they dry? if you spritz with water does that ruin the surface? what can you use to make it stick? and again - THANK YOU!!

Tina

You don't use chocolate. Chocolate will seize..... And it has a low melting point. Candy melts are fake candy and comes in all kinds of color. They have a high melting point and aren't real chocolate. Because of the high melting point they stay hard in the heat.

I never tried candy melts , but when I did the Superbowl trophy I used RI over RKT and it did the job .you can look at the pict. ..sorry don't know how to attach the picture. Look helenecake.