Complex sentence: Brig-sloops are the same as sloops except for their rigging; a sloop is rigged with three masts whereas a brig-sloop is rigged like a brig with two masts.
Split into simpler sentences: Brig-sloops are the same as sloops except for their rigging. A sloop is rigged with three masts whereas a brig-sloop is rigged like a brig with two masts.