I couldn't find conformation that they're illegal, except that the NAHCA rules state that you may not "modify the mast" whatever that means.

What always made me think that they were illegal was the description of them in the Hobie Cat catalog:

"ROTATING MAST FLOAT “HOBIE BOB” Helps to prevent turtling. Displaces 60 pounds of water to keep the mast from going full turtle (mast straight down), even when there's weight on the upper hull. This streamlined float is bracket mounted for easy removal for racing or trailering. It’s bearings allow rotation of the float to act as a wind vane for minimum drag while sailing. This mast float is standard on all Hobie 21 Sport Cruisers. The Hobie mast float will give you the time you need when preparing to right the boat without the worry of going turtle (mast straight down). It also helps prevent damage to your rig and sails that can be caused if the mast head contacts the bottom when capsized."

So...bottom line....I'm not sure! Anyone sure?

Tim