Here's what rhymes with mainskysail.
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 wale detail trail prevail email curtail quail exhale quale bewail braille derail unveil foresail grail impale wassail hightail carrell entail travail gunwale mainsail topsail taffrail pellmell lugsail fingernail pigtail countervail martingale monorail bobtail nonpareil hangnail ponytail swallowtail tattletale