In addition to bringing all the parts into the same file, there are a couple of other things that need to happen to create the sloop. Some of the parts need to have the materials from the hull and the cabin added to them, and all of the parts must have their relationship to the hull defined. Objects that are fixed to the sloop, such as the cabin, will be joined to the hull to create a single object. Objects that move, such as the rudder, will have the hull parented to them.
Let's start by attaching the mast, the boom, and the gaff to the hull:
4909OS_09_sloop_hull_cabin.blendor the file with your hull and cabin.