Why is the {y} needed? I thought that it was needed only if the consonnant pair is forbidden? Sorry if it is a beginners question.{fd} is a forbidden pair, because it is unvoiced-voiced. {vd} and {ft} would be the corresponding voiced-voiced and unvoiced-unvoiced pairs.
Thanks, I didn't check enough "6. Consonant Clusters" in http://www.lojban.org/publications/reference_grammar/chapter3.html ...