[jyl]

So can the boats go faster with wind from a rear quarter than from directly astern? I don't understand how it works.

I have an unrelated question about boats. Assuming a boat is sailing with its hull in the water (not up on the foils), would it be faster if the hull were flexible? My logic is that wind means bumpy water (I think these are called "waves") and vehicles on bumpy surfaces are faster with suspension.