Rhythms is the longest word without any vowel.
Dematoglyphics, miscongugatedly and uncopyrightables are the longest words without repeated letters.
The word which has vowels only is euouae, which is a musical term.
Now let us laugh at the language: Smiles can be considered the longest word as it has miles between s's. But beleagured can be considered even longer because it has a league.