[everforward]

How does one even attach a sail to a cargo ship that would move it at 10 knots? I'm not an engineer so it might even be obvious, but it seems like the mast would have to exert an incredible amount of force on the ship.

Then again, I guess the same applies to old sailing ship and they figured it out. It just boggles my mind.

[gpm]

Traditionally I believe the masts were held vertical by ropes, I imagine the force transferred through them (by tension) not the stiffness of the mast. But I'm far from an expert.