Fairly long words having but a single vowel. (see addenda* for longer words with more vowels)
These were found, in part, through use of the following command applied to dictionary.
grep -i ^[^aeiouy]*[aeiouy][^aeiouy]*$ $w|grep .......
lengths mightn't mustn't schnapps scratch splotch strength strengths stretch that'll this'll twelfth twelfths
* Addenda: fairly long words with only a few vowels:
| two vowels | three vowels | four | five |
first-class high-strung latchstring spendthrift (There are 59 ten letter ones,including: stronghold thriftless thumbscrew transcript transgress transplant triphthong well-known wellspring wind-chill witchcraft wristwatch .) |
backscratcher craftsmanship grandchildren half-and-half knight-errant long-standing self-destruct spindleshanks sportsmanship straightforth strong-minded strong-willed swashbuckling swordsmanship thanklessness thick-skinned thunderstruck transplendent transshipment worthlessness |
disenthrallment great-grandchild horror-stricken knight-errantry long-sightedness loving-kindness notwithstanding prittle-prattle self-government shortsightedness straightforward successlessness thoughtlessness trustworthiness will-o'-the-wisp |
anthropomorphism bloodthirstiness chromolithograph disestablishment disfranchisement great-grandfather misunderstanding poverty-stricken preterpluperfect schismaticalness self-instruction self-sacrificing straightforwardly thermometrograph transcendentalism transcendentalist transcontinental |