J JAC1 Aug 28, 2019 3 Sirius 21 Pioneer Valley Yacht Club Aug 28, 2019 #1 Hi everyone! I just purchased a 1979 Sirius 21. Here's my first dumb question - what's the hull material? I assumed it was fiberglass, but the previous owner's registration for says it's plastic. Can anyone confirm? Sorry, I'm new to all this.