This is the shot where the sail transitions. I did it with a few noise textures and animated a colour ramp to make them change from black to white over about 8 frames and disolve the sail on and off. This then goes into a mix shader with a transparent node to make the sail disappear when the noise texture turns black.
https://drive.google.com/drive/folders/1gNqJKPQ3WS4iymxYmqUtnLQHAgs-EPvC?usp=sharing