I understand, going is not an option.

Well, I think that an e-mail or a letter even might be the way to go. I would start at the beginning with the positive. "Dear dad, I am interested in repairing our relationship..." You know, start with the "I'm not writing to you to make you made."

Then, ease into it. Say, "something happened which you were unaware of at the time I stayed with you. I was young and afraid and didn't know how to share this information with you, and it has taken me a long time to even be able to speak about it to a therapist." That way, he knows it wasn't just him you were unable to talk to.

And I agree with the suggestion to say that he should respond when he feels he is ready.