We berthed at the same marina as Dave for a few years when Tim first bought the yard. It is most definitely at the top of The Hamble and is a quite wonderful quiet motor of 20-25 min displacement cruise to the mouth. What we found was a new learning curve. Yachts under power would just pull out into the flow regardless and I have never worked out to this day if it was, ignorance to the unwritten rules, or flagrant use of the unwritten rules! Like, I have a mast, therefore Motor gives way to sail, but I am under motor way but have a sail therefore am I motor or sail......lets abuse the rule eh?
The sailing training schools on the other hand tended to be more polite, but they also didn't have the maneuverability at all stages to get out of the way of traffic. That's ok because they are slow and will eventually create a hole. That's again ok because heaving too is not so difficult, unless there is a spring tide running...
