Here's what rhymes with mainsail.
fail sale sail veil hail shale vale hale faille male scale mail pale tail tale avail jail nail rail frail gale whale bail stale wail assail bale dale inhale pail snail flail kale unveil wale trail entail email quail quale braille grail impale monorail wassail hightail detail prevail travail curtail exhale bewail derail gunwale topsail foresail taffrail lugsail carrell pigtail ponytail countervail bobtail nonpareil pellmell hangnail fingernail martingale swallowtail tattletale