I have a similar system on my com-pac 23. The boom rolls to reef the main. I'm not real fond of it. I've been told that this was an 80's main reefing system on some of the smaller boats. It is easy enough to convert to a traditional reefing system if you modify or buy a new main. Or you may be able to find a used main with traditional reef points (I did). Then you can keep your boom vang.
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