Looks like you have a pretty good transcription of the Kingston Trio recording, Mr. Happy. The Kingston Trio Close-Up CD says the song was co-written by somebody named "Weissman." No doubt that's Dick Weissman who founded The Journeymen with "Papa" John Phillips and "Flowers in your hair" Scott McKenzie. I have the three Capitol Journeymen albums - apparently, they didn't record "Oh, Sail Away," and there were no recordings of the song other than the one by the Kingston Trio.

The song uses phrases from a number of traditional folk songs, but I don't think I'd say it's based on any one particular song. the Kingston Trio also recorded "Sail Away Ladies" in 1959 for the Here We Go Again album, but the song wasn't included on the LP and wasn't released until Kingston Trio reissues came out. You'll find more information at Kingston Trio Liner Notes.

-Joe Offer-