For anyone who's wondering:

a yawl is a two-masted boat with the after mast behind the steering gear: if the mast is before the steering gear, it's a ketch if the after mast (mizzen) is shorter than the foward mast (main); it's a schooner if the after mast (main) is taller than the forward mast (fore). All clear?

Oh, and a hooker is boat with a style of rigging (which escapes me for the moment), and not, er, something else.

Steve "hands to the futtocks" Parkes