Do epic poems have to a rhyme scheme?

No, epic poems do not have to follow a specific rhyme scheme. While many traditional epic poems, such as Homer's Iliad and Odyssey, do utilize various rhyming patterns, there are also many notable examples of non-rhymed epic poetry. For instance, the Finnish epic poem "Kalevala" composed in the 1800s, is written in a free verse style, with no formal rhyming structure.