I think that maninthestreet is more or less right. From what I've seen recently, things are becoming a bit more tolerant though, at one time some judges used to insist that all the main components had to be home-made before it escaped the 'kit' or 'semi-kit' definition, but that seems to be changing gradually. I'd say that judges at most shows these days would draw the line at a hull you hadn't made yourself, which means that if the hull isn't all your own work, then they wouldn't allow it as a scratch build. The inevitable result of this though, is that scratch build classes often tend to be a bit short of entries.
