Being the owner of the Jeanneau 38 ketch
series which ran from 75 to 82 I cna shed a little light for you.
Rhosyn Mor is heavier, and has a thicker layup
than the newer jeanneus of similar size. The keel
is much deeper, and the ryudder is skeg hung. For her day she was quite radical- carryuing the beam all the way aft. She does have a tendency to pound slightly in heavy weather
( anything above 40- 45kt winds and 12-15ft seas.) THe deck
coring is of decent quality, and 30 years after build there are no deck leaks
. THe galley
is very small by later boat standards, and really has no room for an oven
. THe heads is also quite small, but adequate. At the time she was built Rhosyn was considered a largeish bluewater cruiser, now she would be considered mid size. WE have managed susteained runs of 7.5 -8 knots.