I had the same problem when I got my first Fisher a F30 the wheelhouse window in particular were rotten, as you say a brass block used to join two pieces of aluminium frame hidden beneath a piece of damp canvas lining. I think a chemist would think I was describing a battery. I tackled Northshore about this ( mine was a Northshore built boat ) and they said that was the equipment they were supplied with to build the boats, remember at that time they were building for Fairways. I spoke to some one who had a Pennington built F30 of the same age ( 1973 ) and they said they didn't have any trouble at all. Obviously their window frames has been manufactured by someone who remembered their chemistry lessons. I have a Fairways F 37 ( 1978 ) and the problem is not present in the window frames, so I imagine they had sorted it by then. Regards, Terry