It’s done using ‘boat balls’. Never heard of them? Neither had I, until I found this post at the Old Salt Blog. It seems they’re sailcloth ‘bags’, each filled with a ton of water, and swung out from the mast to heel a sailing boat over on its side. That lowers the masts sufficiently for them to just scrape beneath the bridges on the Intracoastal Waterway.
The video clips below show how it’s done. According to the first one’s description:
The balls get swung out with an initial turn to port or starboard. The tendency then is for the roll to continue by itself, but is controlled by letting the bags out slowly with a line made off to each bag and running through necessary tackle to a cockpit winch.
Ingenious! Here’s a thread on a boating forum with more information.
Peter
I wonder if they could do that with The USS Ronald Reagan (CVN-76) by hanging a couple of F/A-18's over the side?
Looks familiar. See a tugboat go underwater to clear a bridge:
http://www.remedyandcrew.com/rxcruises/towboat/towboat.html .