Is there a type of ship from the first half of the eighteenth century that could be sailed with a crew of a minimum of around 30-50? After doing some research all I've found were ships with crews of about 10 or less (schooners) or at least one hundred (ships of the line). Was there anything in between?
No ship of the line had a crew of 100. Minimum was 350 in the early 1700s, but most of them were needed to serve the guns rather than handle the sails.
All but the largest ships could be sailed by 50 very experienced, very careful, very patient men. 50 men could handle a frigate in a pinch, but 250 men would be needed reef topsails simultaneously, or perform an evolution with all plain sail set.
30-50 could be a typical crew for any medium sized merchantman. A large brig or full-rigged ship, but not an indiaman.
Are you looking for any certain region of ships?