My patterdale terrier dog hates my dad?

I have a 8 month old patterdale terrier and he hates my dad. My dad has tried everything to get him to like him. He takes him for long walks, he feeds him, he plays with him in the house. Usually dogs love my dad. My dog snaps at him, jumps up and bites him, generally just tries to attack him at all opportunities. There are some times where he loves my dad but then he quickly reverts back to hating him. The dog loves both me and my mum and never snaps or growls at us, or anyone else. Any suggestions of how to resolve this?