[alanning]

“Modern mariners can tack against the wind by setting the sails at sharp angles. That wasn’t feasible 2,400 years ago because sails were fixed then.”

From the picture it seems the sail on the replica can pivot around the mast but looks like it would take a lot of work (and time) with all the rigging.

So is this quote’s meaning that modern sailboats can change the angle of its sail fast enough to be useful while the ancient ones couldn’t?

[sandworm101]

There was more to it than just sails. Keel and rudder tech had to evolve too. Tacking a ship upwind is a special thing that involves every aspect of sail and hull to accomplish. And the equipment to do it comes with drawbacks.

[codeduck]

square rigged vessels cannot make way upwind; they are limited to approximately 60 degrees either side of the wind, and would have terrible sailing characteristics in this position that would push them downwind to the level that they could probably not travel a true course within even 90 degrees of the wind.

lateen (think dhow) sails were around from about 200 bc but only became widespread later. They are more efficient efficient upwind and permit a boat to point close enough to the wind to move a meaningful distance "upwind"

[gerdesj]

lol.

You are quite correct - that boat isn't the same as a modern one and you've spotted it. The sail is fixed fore and aft (sheets) and it looks like you move the sheets around as you need. It has a yard which we assume works like our usual square rigged vessels but it doesn't. That vessel can work upwind a bit.

Zoom in on the modern yacht in the photo. It's staysail (front triangle) is luffing slightly (laminar flow is broken). That means that the old boat is working fine at the same point of sail as the modern boat. The old boat probably doesn't have a decent keel so will slide sideways a bit.

This sort of analysis needs proper sailors involved and it looks like none were.

[simmerup]

It's too much to expect an academic to engage SMEs