I have not had much luck with RKT. If I just cover them in fondant, they turn out really bumpy. If I buttercream coat them, then they tend to fall apart. Don't know what I'm doing wrong. Any suggestions?
You REALLY have to pack them tight. After that, you can coat the object with melted chocolate or candy melts. Just paint it on. Then fondant or gum paste. 
This boat is my most recent rkt object
http://cakecentral.com/modules.php?name=gallery&file=displayimage&pid=1510758&sub=1510763
Thanks to both replies. WOW, diane706, your cake is awesome! I can only aspire to that someday. Right now, I'd be happy if my RKT didn't fall apart. The melted chocolate is a great idea. I had tried RI before, but it didn't hold. Next time I will try the chocolate. What type of fondant do you use? I love working with Satin Ice...just don't like the price. Do you make it or buy it?
Thanks for that nice compliment! I use Fondarific fondant for covering cakes. LOVE the stuff! It's wonderful to work with. I've been decorating cakes for many years and have experimented with lots of different fondants. This is the one that I have FINALLY settled with. Anyway, for covering RKT objects that won't be eaten, I use gum paste for the final covering. This is a stronger medium that will "hold things together".
I took a class from Colette Peters and these are the suggestions she gave the class:
1. Cut down on the butter as that is what keeps the treats soft.
2. Use a bit of corn syrup to help set it up as corn syrup hardens when exposed to air.
3. Let the shape you make harden a bit before applying fondant to or on it.
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