"Jeff, these don't have fin keels, they have full keels with a cutaway forfoot and skeg hung rudder. They point with the best and have one more races than many designs out there. I think you confused the K's with something else. Go to http://www.kettenburgboats.com and check it out."
With all due respect, I know the lines of a Kettenberg quite well. While there is a tendancy these days to call any boat with an attached rudder a "full keeled" boat, there is no resemblance between the keel on the Kettenburg and a full keel. In the days when the Kettenburg was designed (and I began sailing) a fin keel was any keel whose bottom was less than 50% of the length of the boat (sometimes quoted as 50% of the horizontal length of the sailplan) whether or not the boat had an attached rudder or not.
Look at the profile of the Kettenberg 38,(visualizing it without its rudder)
Or the Kettenburg 46 for that matter:
and compare it to the Cal 40.
You will see that the Cal 40, which no one denies is a fin keel, actually has a longer horizontal proportion than the Kettenburg. If you read Lapworth's contemporary descriptions of why he went to a spade rudder on the Cal 40, it was because he had been racing fin keeled/attached rudder boats like the Kettenburg and they were so foul handling that he sought a better underbody design that would improve handling and tracking. The Cal 40 was a revolation compared to these fin keeled/attached rudder boat (as they were called at the time that they were designed) because these early fin keeled spade rudder boats actually tracked better and were much easier to steer by virtue of having a much greater longitundinal monent of interia to their lateral plane than the boats with attached rudders.
In terms of hull sections the Kettenburgs had very similar cross sections as well, with comparatively firm bilges for that era, with a comparatively large fillet whether the keel joins the hull.
So while it is popular to rewrite history and deny that these are fin keels and these days to go so far as to call them full keels, that whatever you may chose to call them, it does not change the fact that these extremely short length keels/ with attached rudder boats are a real bear to sail in light conditions and at the heavier end of the wind spectrum. Add in the full ends and short waterline you end up with a boat that will not hold a course without a lot of tending and which is hard on a crew. There is real virtues to a well designed full keel, but calling a boat like this a full keel, even though it lacks all of the virtues of a full keel, is insulting to real full keels.