Joy asked me the other day if we should make the white version of the full petticoat as described in this tutorial as a full circle and not a half. After all, these petts go under full circle skirts.
There are several technical reasons why, and also why we don't gather the petticoat heavily at the waist either.
If you look at the way a full circle skirt falls, part of its charm is all of the folds that gracefully fall along its length.
See all those lovely rippling folds at the hemline? They are GOOD! And they look so lovely sitting out on the support of a full pett.
Now imagine if all those folds had frills sewn to them. The frills would also fold in and out and in and out, and these folds would be all ridgy and uneven. Lovely on the skirt, but lumpy when underneath.
So, a half circle, slightly gathered at the waist, is ideal. It will give you a nice cone of fullness to support your skirt. Too much gathering at the waist and we're back to the folds problem again.
Now FULL, gathered skirts, they are a different story, and one I am not telling here :)
Full gathered skirts have slightly different petticoat rules. :)