There are, as I understand, three "schools":
1 - vav is always [v], also in words like השתחוו ,ופוה, ייקוו
2 - vav is [v] except AFTER u, e.g. in ופוה, where it is [w]
3 - vav is [v], except BEFORE AND AFTER u, so in ייקוו, ופוה, השתחוו it is [w].
(Words like רוח, נוח are a different matter - here the (unwritten) glide is always [w])
Which "school" do you follow on this website?
From what I've heard - and seen in G. Khan's book -, you probably follow school 1 or 2, I'm referring to ייקוו [jiqqɑ:'vu:].