Cats are out again

hi all thanks for this video. just a question what is this ball on the top of the boat ?

Thanks for posting. I am new to RC sailing and want to get one of these. Did they require extensive waterproofing before use? If so, how and where?

Fun to see the Force 60's on the water.  Thanks for posting the video.

Plizzz more wind ! and Joysway, plizz build them larger ! (mini40)