Re: Urbanna for marina location
that dag gone channel in and out of Deltaville is such a pain, and like Caleb mentions, you really have to watch the depths. Urbanna has a lot of touristy things to do, and several festivals a year. There is limited slippage in Urbanna proper, but those are pretty decent weather holes for the most part. The town dock and area can get crowded quickly.
Couple of hours to the bay, and not near as wide as the Potomac so if you get to the bay and it looks ominous, you are pretty much compelled to head back up the river instead of across. Short sails, but that can hone your tacking skills. I don't recall much current one way or the other. You will get some wind tide every now and then.
The York may be a better choice, time wise from Richmond, with similar sailing and facilities to the Rappahanock, Deltaville excluded.
Best of luck