The thought of building a siege engine is very exciting. I am in a group with Zak Rider and myself. We are having thoughts of building a ballista, but there are many things that can go wrong when building such a complex siege engine. For example, the wood might not be strong enough for the tension placed on the wood. And there is a possibility that the machine might not even work if it is not build to a high standard. But I am looking forward to building my first prototype.